Login to VeloClub|Not a member?  Sign up now.
December 15, 2017
December 14, 2017
December 13, 2017
December 12, 2017
  • raphanatic

    the pro peleton fly down massive mountains at very high speeds – does anyone know how much melting of carbon wheels happens with them? I don’t recall any events. Perhaps they’re all too light and don’t brake much for rim overheating to be an issue

    • Andy Logan

      Most if not all would be running Tubs, so no problems when it comes to heat.

      • jules

        pros also have good braking technique, i.e. not dragging the brakes down the hill to wash off speed

      • reippuert

        = all of them will be running tubs.

    • James Huang

      Very little, if any, I’d say. But keep in mind that you’re talking about the lightest and most skilled riders in the world. They’re hardly representative of the norm.

      • George Darroch

        And we go faster downhill, because we’re heavier. At least, *I think* that’s how it works…

        • James Huang

          Nope. *In theory*, we descend at the same speed no matter what we weigh. A heavier rider will have more kinetic energy at the same speed, though, so brakes have to do more work for the same amount of deceleration.

          • David Morse

            Hi James. It’s typical that rider CdA will not increase proportional to an increase in weight. It is possible – and common – that a heavier rider will experience an increase in gravity’s force (relative to a lighter rider) without experiencing a matched increase in air resistance. Meaning – heavier riders will descend faster than lighter riders, much to the same effect as a bowling ball will freefall faster than a feather (unless in a vacuum).

            • James Huang

              Oh sure, David, go ahead and toss real-world air density into the equation ;)

            • Steel

              We’re getting close. It’s buoyancy that is the difference, not mass. Buoyancy is all about density. Kg/M3 of rider.

              Density difference between light and heavy riders is marginal and counteracted by aerodynamic drag.

              I can descend faster at 74kg than 78kg, because I can hit turns fasterand brake later.

              I’m going to start a webpage just to clarify this question forever more.

            • markpa

              I’m guessing many have already seem this but it’s still excellent viewing https://www.youtube.com/watch?v=E43-CfukEgs

          • Arthur M

            Allow me to correct you, it’s not speed which is constant no matter the weight, it’s the acceleration from gravity.
            If two people have the same aerodynamic one their bike but different weight, the heavier rider will reach faster speed when descending.

            You will reach your final velocity when the gravity force (which is a function of you weight) equals the friction force from the air (not function of your weight, but function of your speed and aerodynamic).

            You are correct about the braking part tough.

            Edit: Didn’t see that David Morse already corrected you

      • Spartacus

        They are also all on tubs, certainly for mountain stages

    • JS

      One of the biggest reasons for this is that Pro’s are in race situations where they don’t need to brake as much as a regular rider – open roads to allow better sight lines, never getting caught behind really slow cars or riders, and just being better skilled and not scared of descending, which is still a reason many keep their brakes on. BUT, when you look at what happens when the pros need to keep their brakes on during a descent – 2015 Tour of Oman neutral roll-out is your answer. Failures galore!

      The first three years Rapha offered Randonnees, I was the guy leading the French ones (and in on a few others too) – during that time, ~15 trips x 6-12 riders, we had only one pair of carbon clinchers that made it through a trip. He was a very capable rider / skilled descender, but if we’d had fog on a descent, I’d still have swapped him to alloy. All the others, and there were a great many, failed – one catastrophically (sorta like that test). It was to the point that we offered wheel swaps at the top of cols and if we had a rider who insisted on descending on his carbon clinchers, we’d quietly keep a guide with him on the descent, so we could be there if/when he started to feel the pulsing of a void section of rim.

      Yup – 20 years on, and still not ready for prime time.

      • redhead322

        Wow, thank you for sharing the about the Rapha Randonnees. I’d never descend a mountain pass in carbon clinchers either. A blowout there means the tire is coming off… and at those speeds that would result in a nasty crash.

    • Ben Colman

      They are running on tubular rims. Due that, the stopping surface its not in lateral
      contact with rubber.

      • reippuert

        + tube is not exposed to the heat absorbing rim.

  • Noah Sears

    It’d be cool if there was a way to move the braking surface away from the rim somehow.

    • Carl Sechrist

      Like near the hub, away from the spokes?

      • James Belford

        Has this been invented.? We should all go with this new-fangled concept.

        • Sean

          It will be to dangerous

    • Marco Kall

      But what should we call this new system? Maybe we could replace the brake cables by hydraulic fluids. And use some sort of small metal rotor for braking…

      • tanhalt

        Hey! Here’s an idea…what if the metal braking surface was made as large of diameter as possible and then INTEGRATED into the rim itself?? Just think, then the calipers could be centrally located on the fork and frame in the strongest locations, AND they could be made much more aero as a system. That sounds like the logical performance evolution, no?

        • Nathaniel Bacon

          I need to go check one more time, but that sounds just like my HED Jets.

  • Ragtag

    Good article and view point.

  • Neuron1

    Any information on Campagnolo wheels?

    • James Huang

      Sorry, not from me. But that just furthers my point: you shouldn’t really have to ask, should you?

      • Doubtful Guest

        Who asks? If had a friend crash from a latex tube blow out, it wouldn’t make me ask if all latex tubes are prone to blow out. If I had 3 friends with similar experiences, then I’d ask.

        This was a strange article, and a reverse-engineered test, but the upshot is a lot of free advertising for Alto. Win-win?

    • MarekK

      Ze germans in bike/tour magazine have done testing of carbon clinchers a couple of times – plenty of top brands with spectacular failures. Campagnolo (Bora One IIRC) came out as one of the few that didn’t fail the torture test. Bike also tends to be pretty good at defining extreme but realistic conditions… the usual german highly technical approach. Article was from 8/2016.

      • Neuron1

        Thank you, I’ll look into that. The reason I asked was because Campy is famous for over engineering things to hold up in the real world, despite the equipment being marginally heavier it is sturdy.

        • Antti Salonen

          Current Campagnolo Bora as well Fulcrum 40 and 55 carbon clinchers are remarkably light though. My Fulcrum 40C’s are 1370 g, which is really quite light for clinchers with a wide rim and 40 mm profile. I don’t think there’s a lot of over-engineering in there, but good engineering no doubt.

          That being said, where I live there are only small rolling hills. When I go to anywhere with long descents, I switch to aluminium rims.

      • Bobby Sweeting

        We really wanted to test a Campy rim but weren’t able to get our hands on a new one! Hopefully we can find one in the future and amend the video to include the results! I’ve heard that Campy and Shimano both do very well in heat transfer testing.

    • Bobby Sweeting

      We really wanted to test a Campagnolo rim but weren’t able to get our hands on a new one! Hopefully we can find one in the future and amend the video to include the results! I’ve heard that Campy and Shimano both do very well in heat transfer testing.

  • bigstu_

    Before we get hung up on what constitutes “real-life” conditions, would you drive over a bridge that had only been designed and built to “real-life” conditions?
    Automobiles are typically designed with a factor of safety (FoS) of 3.0, pressure vessels with an FoS of 3.5 to 4.0, and buildings with an FoS of 2.0 for each structural member – but only because loads are so well known (since we’ve been constructing them for several thousand years).
    So why does anybody think a wheel designed with an FoS of 1.0 is desireable???
    And if you are a wheel manufacturer that wants to demonstrate the suitability of your wheels, don’t bother showing me examples of the lightest and skinnest Pros who do their best to brake the LEAST.
    Never settle. And, as always, enjoy he ride.

    • fat coppi

      Planes have a FoS of 1.1. Just something to remember before take off ;)

      • bigstu_

        Yep, the ‘ol lets trade safety margin for weight/$$$ what could possibly go wrong?

        • jules

          for carbon wheels, I reckon there should be 2 categories of wheels:
          1. race wheels, which are mostly what we have
          2. descending scares me a bit and I weigh 100kg wheels, which account for cyclists who ride the brakes down steep hills, and which won’t explode as a result.

          • Wouter Em

            They probably could make those wheels and they would be as heavy as or maybe heavier than aluminium rims. So would you deck out the extra cash for a set of flashy carbon ones? Didn’t think so. Carbon is bling and light weight so it’ll always have slight trade-offs in other areas. I think wheel manufacturers are doing a nice job keeping the balance sensible. This Alto test is a nice piece of marketing gibberish but that’s it, wouldn’t pay too much attention to it.

            • James Huang

              The sad thing in all of this is that Alto may very well have done some fantastic development work here in terms of the heat durability of a rim-brake carbon clincher rim. But unfortunately, there’s so much skepticism around the topic in general that it’ll be hard for the general public to immediately accept the claims at face value.

              • Larry Theobald

                It would have been interesting (though certainly not in the companies best interest since they’re selling carbon) to see this test run on a conventional aluminum rim/wheel. We’ve all heard the myths and legends of tires blowing off (usually this involves a tandem) due to braking heat, but the closest thing I’ve ever seen was a guy squirting water from his bottle onto his rear brake/wheel and watching it turn to steam. This was on a long descent after a Giro stage so there was lots of traffic and I’d guess the guy was dragging the brakes way-too-much? But zero evidence of failure, unless you count the failure of the dolt to move away from the center of the road while he was watering his brake!

          • Chris

            We have #2. Disc brake wheels.

      • Cody Leuck

        Aircraft have specific operating envelopes that are strictly followed. With a bike any Jane or Joe Blow, of any weight and any skill level can do whatever they want. Yet any failure that occurs is often believed to be a manufacturing or design flaw. Correctly using the right (quality) tool, for the right job is conceivably a part of the problem.

    • Nemeseri Andras

      In this case the comparison would be better with Formula 1 race cars. These wheels were design to give the best weight, aero performance and safety combination. Everybody knows the solution to safer breaking: massive alloy rims or disc brakes. They both will be heavier and less aero. These wheels were designed to be fast, light and to be raced. If you are not a racer or don’t know how to break properly you shouldn’t ride these.

      • Ragtag

        Formula 1 race cars are not sold to amateurs to race around on open roads, so the comparison may not be appropriate.

        • Nemeseri Andras

          You are right, but plenty of cars designed for racing are available for the public. It’s like complaining about open traffic breaking performance of a Porsche 911 / Ferrari from 200 mph. If you are stupid enough to use a racing equipment on open roads without proper experience it’s your choice.

      • donncha

        Except that racing cars have better braking than normal road cars, the exact opposite of bike wheels.

  • Mr Fisher

    About 10 years ago I had a Lew tubular rim problem descending Sonora Pass. Up to 27% grades with lots of corners at over 9000 ft. It started to delaminate, thump thump thump on the rear. I weighed 155 lbs. I stopped and let it cool and opened up the rear caliper brake. I am an expert descender, Cat 1 for 10 years, winner of the Death ride and Transalp. I start again and try not to gain much speed and try to go no handed with my arms spread to slow my self. made it to Lee Vining that day and did Tioga pass the next day on the same wheel and back to the start in Sonora. If I had been on the clincher version it’s likely the rim/tire would have exploded!
    In my experience, high altitude, steep twisty descents are a great real world brake test, or a 250 lb rider who feathers their brakes and wants to go safely slow the whole way down. The un-real acid test is to try the wheels on a tandem.
    Your right on about standards.
    All said no way I would want to ride that pass on a carbon clincher rim with rim brake, I just don’t trust it.

  • Mr Fisher

    O yeah, Altitude, I have done Sonora back in the day with the first Campy sidepulls and alloy tubular rims. I was at the limit of the profmance of those brakes. the rims got so hot! The air cooling is much worse at altitude.

  • bigstu_

    Isn’t a high temperature resin supposed to be less ductile? So how durable are these wheels in comparison to others?

    • James Huang

      Even if that’s the case, I’m not sure how big an issue it would be on the road since those rims would rarely see impacts.

      • bigstu_

        Unseen and unavoidable potholes in early morning twilight bunch rides often have nasty sharp edges that transmit shock loads to the rim. More common than you think. Remains a mystery to me why people don’t use training wheels for such things but there you go.

        • James Huang

          I’m not saying it doesn’t happen. But it’s not usually a primary design concern for road wheels.

          • Nazgul350r

            I seem to remember a 3 spoke wheel failing do to a rim strike. ;)

            • James Huang

              Several, in fact.

    • Bobby Sweeting

      Yes! They are slightly more brittle. We had to offset this in our laminate schedule to ensure that our rims remained able to pass our internal impact testing. We are UCI qualified to 40 Joules (the video is on our Facebook page) but that is honestly an easy mark to hit. We test every product that we sell to 90 Joules of impact without delamination or lateral/radial runout over 1mm.

      • bigstu_

        This is tremendous news and worthy of an amendment to the original article to emphasise that point. Being able to improve product performance in one area without compromising another is highly commendable. Thanks for the additional information, it’s elevated these wheels to the top of my consideration. Now if I can just lose enough pounds to get on them…

        • Bobby Sweeting

          Thanks Stu! We would have loved to include more info in the video about our new rims, but we honestly didn’t want to have any promo material in the video itself. We really wanted it to be an unbiased study, not an advertisement.

          Also, we’d love to help you lose those pounds! All of our wheels have an unlimited rider weight and are tested up to 400 pounds of radial load per wheel. So you have nothing to worry about, and can hop on a set whenever you’d like!

          Please let me know if you have any other questions at all. I’m more than happy to help!

          • bigstu_

            Making it hard to say no Bobby…

            • Bobby Sweeting

              Haha, I do what I can! Our R-Symmetric hub geometry gives the wheel so much more balance and responsiveness. It’s amazing how stiff they are, even under the biggest riders. If you’d like, just shoot me a message through the contact page on the Alto website. I’ll make sure you get set up with something that will be perfect for your needs!


  • jules

    I’m always dubious of claims that a given carbon wheel resists over-heating. There are some unavoidable fundamentals with carbon wheels and braking:
    – braking energy is converted into heat energy. you can’t avoid that.
    – heat energy tends to… heat the rims. this causes rim temperature to increase.
    – the rate of temperature increase depends on a rim’s heat capacity (can’t remember the tech. term – the amount of material available to spread the heat through) and heat dissipation properties.

    basically you can make some gains with material properties, but I suspect those are mostly a given and gains are small between wheel brands.

    the major gain is in heat capacity, which you can increase by adding material, which adds weight. and heat dissipation, which is linked to rim shape/profile.

    there’s not a lot to play with there. whenever I hear a wheel manufacturer claim big gains in carbon heat management, I am suspicious. I can only guess they’ve got a heavy rim with more material in it.

    • James Huang

      In what I’ve seen, carbon rim makers don’t usually claim that their rims don’t heat up as much as others; rather, that they’re better able to handle the heat without falling apart.

      • Ragtag

        Yeah Carbon wants to disguise itself as Alu in that use case. :)

    • James Browning

      It all depends on the grade of CF being used, working in the space industry we get to design with fibres with a thermal conductance higher than that of aluminium which result in a structure which feels like aluminium to the touch and not like plastic (it feels cold as it dissipates heat very quickly). However, the raw material $/kg would blow your mind!

    • Il_falcone

      Watching Alto’s video and seeing their test results shows that their rims just stay much cooler when the speed is very similar to the speed reached by other wheels. This last part is important as it indicates that – if the motor is always providing the same power – the decelerating power created by the brake is also (nearly) the same. So same power, same speed, but significantly lower temps means the heat conduction in the rim must be much better. Making the heat spread into the whole rim faster seems to be the key improvement here. The surface of those aero rims is big enough in order to dissipate that amount of heating power through radiation and heat conduction. The fact that those rims are all more or less black also helps to increase the power that can be dissipated through radiation. But for this to happen it’s important to spread the heat all over the external surface of the rim to increase the surface that actively radiates and conducts that heat away from the rim.

      • Yeah, it pretty much needs to be that they radiate heat better, or else they have some super high temp resin that no one else is using yet. If they are able to radiate heat better, it’ll be interesting to find out more about how they have achieved that. My understanding is that carbon isn’t a great heat conductor, and that is particularly true when you are talking about cross fiber conduction in a unidirectional ply. There was a company that was doing radially embedded copper wires in their carbon rims that would conduct heat from the braking surface down toward the spoke bed. Can’t recall the name of the co. but I think they were Swiss perhaps, although this was a few years ago and they don’t seem to have revolutionized the industry with the tech, so I am not sure how effective it truly was.

    • Bobby Sweeting

      Those are good thoughts! I just wanted to pop in to say that our new rims actually use less material, and are slightly lighter, than our 2017 models! This is because the resin additives allow it to flow more readily throughout the matrix, so we can use less of it to fill all of the small air gaps. This tight compaction is what gives the rim better heat dissipation properties without forces us to increase the number of plies in the laminate schedule!

  • Jobu

    I guess this is one reason why everyone should run disc brakes with carbon rims.
    Is there a real weight advantage for the low profile carbon clincher runs vs a similar aluminum rim? I can see it happening on the deep dish ones.
    Those spokes have a lot of tension, more so with the lower spoke count wheels and drive vs non drive side. Is there any worry about some kind of plastic deformation with carbon rims?

  • Warwick

    With all the R&D and “expensive resin matrices” etc going into carbon clinchers we don’t yet seem to be getting a cost advantage in disc specific rims, which should be expected shouldn’t it? Enve and Zipp (as an example) charge more for the disc versions of their wheels which obviously don’t need to be built to resist the same amount of heat, or have as much manufacturing time spent on making brake track to exacting tolerances.

    • Jason Rico

      But other factors come into play with disc brakes. For example: The spoke bed now needs to be stronger and thicker to resist the wind up and twisting of the spokes during braking. With a rim bake you don’t have that issue.
      Also, because in current disc brake bike applications the user is ‘likely’ to use the bike off road (Gravel, CX etc) and when used this way the impact resistance of the rim but also be increased, usually with a more expensive resin.

    • Bobby Sweeting

      I’m not sure about those guys, but I can tell you about our own production costs! The rim cost works out to be about the same, as we use the same resin and construction process as our rim brake models. The disc brake hub, however, is must more expensive because of the rotor tabs and added machine time. That’s why our disc brake models are marginally more expensive than the rim brake models!

      • Warwick

        Many thanks for the reply Bobby. There is a slight cost in the difference between non-disc and disc hubs, but it is slight, at last check CK R45s were about $100NZD more for the disc set.
        But I was focussed more on the rims, and your comment does somewhat illustrate my (poorly made) point. Why use the same resin and construction method for a disc rim? It doesn’t need to dissipate heat, or resist any clamping force (although I’m guessing that may be negligible?) Why not design and manufacture them totally differently, using a different resin, less material for lighter rim weights, non traditional flat side walled designs etc.
        I’m not getting at you or your company just more interested in why the industry hasn’t gone this way, yet.

        • Bobby Sweeting

          Absolutely, I’m always happy to chat. You’re correct, many rim manufacturers use a lower quality resin, lower quality mold (aluminum instead of steel) and lower quality building technique (machine built instead of hand built). They may charge more because they can, and simply improve their margins. For us, the resin properties come down to more structural improvements than just heat transfer. The resin additives allow it to flow better throughout the matrix, which fills gaps and voids to improve impact strength. It also allows us to use less of it, which makes the rims lighter. To answer your question, we COULD use a completely different process with our disc brake rims and likely get away with it, but that’s not what we’re interested in doing. We want to release the best possible product that we’re capable of!

          As far as the profile goes, are you referring to a hookless design? If so, you’ll notice that we did that for our new disc brake rim models! Check out the profile on our CCX line, which is a high press hookless profile that can be used with our without a tube. It is disc brake specific and about 100g lighter than a standard hooked clincher model.

          I hope that helps! Please let me know if you’re curious about anything else at all.

  • Robert Merkel

    Interesting article.

    That said, there’s a safety margin, and there’s overkill. The Enve wheels lasted over five minutes, and the rim was over 300 Farenheit by that stage. Wouldn’t that kind of heat have blown the inner tube long before the rim deformation happened?

    • Il_falcone

      But the inner tube did not fail in the test.

  • Husain Bushehri

    What Alto is doing is trying to be a Volvo: they are marketing their product’s safety through spectacular crash tests. As for real life studies, maybe someone needs to look in detail at the wheels used in events like the Haute Route or Maratona delle Dolomites. Surely they feature they toughest testing ‘real world’ conditions.

    Of the thousands of riders, how many are on carbon clinchers? new or old? what percentage of riders experienced delamination?

    • by7

      my personal experience at Haute Route was that my carbon clincher (China made stuff) began to “melt” mid way Stage 1 and by end of Stage 7 it was completely toasted…
      I am good descender with 30 years racing experience, but racing in unknown roads open to traffic obviously requires some feathering time by time…
      That rim was only the 1st of a long series of carbon clincher who did fail… Now I use a pair of Campagnolo Bora and let’s see how they goes (and I keep a pair of Shamal Mille ready for mountain events…)

  • Ross

    Raoul from Luescher Teknik has some good info on his website and also a youtube channel about carbon wheels (and frames). It would be good for CT to interview him.

    • Check the podcast archive, there was an episode that featured Raoul maybe a year ago or so.

      • James Huang

        Yep, I think I’ve included him two or three times in various articles now. He’s an incredible resource.

  • Cruz er

    Riding the Santa Monica and San Gabriel mountains with frequency. I will tell you people destroy carbon wheels all the time. It doesn’t matter the brand, I’ve seen them all.

    Raoul from Luescher Teknik calls carbon clinchers “Black Metal” or “Black Aluminum”-meaning the design copies an aluminum part without consideration that it is carbon fiber.
    This is true. If they were designing a clincher carbon wheel from scratch (and aluminum did not exist) what would it look like? Nothing like it does now, for sure. They cannot solve the issues without significant R&D, which they are not willing to do. 20 years tells us that is the truth.

    I don’t think it’s a coincidence that the industry made the hard sell on wider, lower psi wheels and at the same time moved hard towards discs. It is much easier to reduce the stress on the clincher with lower psi, and move the braking to a disc. Solves a lot of problems and makes sense for the industry.

    Brake pads and surface treatments are just band-aids to prevent liability.
    I applaud Alto because they did something, as James H rightly pointed out, should have been given within the industry over a decade ago.

    • Hroch

      Well I wonder how long would a disc brake last before failing due to overheating in a test designed like this- constant braking of 1200W of power.

      • James Huang

        In that context, a hydraulic disc brake would most likely begin to fail due to the fluid heating up to its boiling temperature. In that situation, you’d progressively lose hydraulic pressure, but nothing would catastrophically explode. Also, once the system cooled down so that the vapor turned back into fluid, the system would work again.

        • Il_falcone

          At least according to my experience with current brakes you are likely to damage (dish, soften) your rotors permanently if you continue to brake while waiting for the “warning sign” that the boiling fluid and loss of pressure / vanishing point of engagement formerly was. That’s maybe due to a) using materials for the pistons which conduct heat much less into the fluid than massive aluminum pistons did back in the days and b) designing the pistons so that they touch the back plate of the brake pads only with a ring surface and not with their full face anymore.
          I recommend riders to give their brakes some respite when during a long descent their sound suddenly changes or they start to fade. If you stop then you usually get away with a brake that when back to lower temps will work like it did before you cooked it.

        • Larry Theobald

          At Interbike 2017’s Tech Seminar Campagnolo showed photos from hydraulic disc brake testing they conducted. They admitted the loads and forces their testing applied were far in excess of what could happen with a bicycle and rider but clearly showed Company X’s product completely destroyed with Y’s severely roasted but still functional while Campagnolo’s looked barely used. They declined to reveal the names of the other brands tested Results and conclusions similar to this wheel test – a demonstration of superiority, but not necessarily in a way that’s related to real-world use.

  • J Connell

    I have worked for years in bike shops near the Alps and I have seen many brands of carbon clincher rims heat damaged. Often the client will report that she/he had used these rims without problems for thousands of kilometres, only for it to fail when he/she was on a cyclosportive or cycling holiday, ruining the trip. Sometimes the client is not used to descending and will drag the brakes excessively, or they will be stuck in a group that descends too slowly, forcing the rider to brake excessively. But even amongst expert descenders riding in competent groups there are still problems due to unexpected hard stops or decelerations. On open roads mid summer, one might be forced to brake violently due to a car full of tourists stoped for photos mid hairpin, or one might be forced to brake excessively when stuck behind an RV or farm vehicle through a series of tight turns. Few riders will have problems under perfect circumstances, but on the hottest day of the year, stuck behind a slow group or vehicle on a long descent, carbon clinchers just might try to kill you.

    Certain brands are catastrophic, but even with some of the better carbon clinchers in the business (campag and zipp) you get inconsistent/diminished brake performance when the rims heat up and are never quite as confident as with a good pair of aluminum rims. If the client insists on deep section carbon, push them towards tubs for the mountains. If they are open to shallow clincher rims, push them towards alu.

    • Il_falcone

      I agree with much of what you say here. But certainly advising “normal” riders to opt for tubulars to be used for alpine riding is outright dangerous. Even professional mechanics who glue a lot of tubulars sometimes get it wrong and as a consequence tubs hop off the wheel or rotate on the rim and tear off the valve. Tubeless tires on aluminum rims is the safest solution for bicycles with regards to brake heat. They can deal with even more heat than the best commercially available disc brake setups.

      • J Connell

        Living and wrenching at the foot of the alps, I am certain that carbon tubulars are safer than carbon clinchers for the mountains. That said, aluminum rims are safer still and a better choice for most rim brake applications.
        The high end road market here is still mostly tubulars, for weight, tradition, and safety reasons. It is a point of pride for locals to ride tubulars at all times. It blew my mind when I first moved here, but with a professional, multilayer vittoria mastik one glue job, there is very little risk for even a large rider of rolling a road tub. In the event of a flat or blowout with a tubular, deceleration can be carried out in a far more controlled and safe manner than on a flat clincher tire. Heating the glue enough to rotate the tub with braking force is sadly a possibility. Typically the tub will start to bunch up behind the valve before it tears and the rider will sense a thumping sensation from the wheel. Only if he/she continues braking hard will they manage to shear the valve. Looking at the state of heat damaged tubular rims (both clincher and tub) that have passed through my hands and the weight and rider profile of the clients who have brought hem in, I strongly suspect that the client who will catastrophically liquify tub glue on carbon rims will also risk exploding carbon clincher rims of similar quality. And if the client insists on latex tubes, the tubulars look even better as the heat sensitive latex tube is protected from braking heat when sewn up in a vittoria or veloflex tubular.

        • Il_falcone

          I certainly did not want to doubt your experiences. They are surely sound. But what I meant is that glueing a tub to a carbon rim so that it can be safely used in the mountains is a job for an expert who definitely knows what he’s doing and is aware of the responsibility he has for his customer’s life. I doubt that even regular average home mechanics are up to that job and to be honest the vast majority of today’s shop mechanics certainly are not.
          If a rider on a tub manages to puncture a tub during a ride or an event in the mountains and then decides to install a new tub in order to be able to continue that ride or for the next day I would not consider this to be safe at all.

          • Gluing tubs isn’t rocket science it’s contact glue. Follow the right procedures and you’ll have good results.. the other thing is to check the glue job before using it. If it’s not worked as it should it’s easy to spot.i take tubs for big mountain riding. Secret is if it’s an important event put new tires on..

            • Kayrehn

              Yup, it isn’t hard at all. I’ve seen many YouTube videos of proteam mechanics gluing on tubulars and I definitely take more care in the glue application compared to their swift brushes over the rims.

          • reippuert

            Gluing is not rocket sience.. its just a bit messy.
            The main problem for non pro mechanichs will to to a straight glue job and avvoid a minor thumping arround the valvle.

            Besides toufo tape is quite easy to do roadside and very safe.

      • reippuert

        Risk of fatal disaster on any tub no matter how lowsy the glue job is is far less than risk of a clincher blowout on aluminum rims. – The latter will happen before the tubluer glue overheats enogh to leave them rim. And you will certainly feel if the the glue is beginning to melt and hav ample time to brake from high sppeed before the tire leaves the rim.

        Tubless rim brakes on both carbon and aluminum is way more dangerous than tubular. Clincher and tubless suffers from the same design flaws.

  • lefthandside

    James – are tubeless carbon rims much safer?

    • James Huang

      In the sense that there’s no flimsy butyl (or latex!) tube to melt and blow up, yes. But in terms of the rim’s structural integrity due to brake-related heat build-up, no.

      • reippuert

        Could actual be even more dangerous. All it takes for the seal to brak is an overheaed tyre bead. And that blowout will be even faster than with clinchers.

        in my humble opinion: carbon rimes requires either disk brakes or tubular tyres.

  • DT

    I noticed that the alto wheel speed during the test was about 1mph higher than all of the other wheels. So doesn’t heat up as much but also doesn’t brake???

    • Il_falcone

      That’s a minor difference. The friction coefficient on their rims seems to be a little lower. But the decelerating power the wheel has to deal with is the same as power = (friction) force times speed. If the motor supplies the same power (1200 Watts) and the speed is kept constant at a relatively low level (where the rotational aerodynamic drag of the wheel is insignificantly small) then that power is transferred into heating power.

      • DT

        Works about to be about 5% better friction force.

        • Il_falcone

          Which only matters if the force which your hand controlling the front brake is capable of is very low. Otherwise you’ll have to pull that lever just that tiny little bit harder. With contemporary rim brakes even riders with somewhat weak hands are able to create a higher friction force than what the bike is physically able to transfer to the ground without the rider either launching himself over the handlebars or locking the front wheel up if he manages to lower his COG significantly.

          • DT

            I think you’ve missed the point.
            All reviews these days comment on the braking performance. What alto have done is lowered their braking performance in favour of heat management.

    • PBI

      You are absolutely right !
      As an Engineer, I have to explain how an eletric motor works ! Cause this testing is just a Fake Article to me !
      1200W is a nominal input power. If the motor is not controlled by a constant electrical Intensity, the real power of the motor differs from one test to another, depending how good is the braking performance of the Wheel.
      The Bontrager for example has good braking performance, so the temperature is getting high quickly, and you can see the speed decrease cause the motor faces strong resistance. The motor maybe consumes 1200W at the time.
      With the Alto rim, the speed not decrease, The motor doesn’t face much resitance, It maybe consume just 600W during the test.
      Without any resitance, the motor would consume 5W to turn freely at maybe 22mph. The speed of the motor is controlled by the voltage, and whithout any resistance, the Wheel wouldn’t turn at 50mph !!!
      Just don’t believe small brand with fake testings ! Trust famous companies, they do real testings ! ;)

  • Antti Salonen

    The really interesting bit for me are the temperature graphs at 18 min 2 s of the video. The Boyd wheel was at 300+ F and still going up fast, seemingly unable to dissipate the heat. Based on that graph alone, I would never-ever buy that wheel if I had to do any serious descending.

    Enve and especially Zipp look like they could’ve made it. They both stopped heating, never got really hot, and Zipp was already cooling when it failed. You can argue about the validity of the test protocol, but it does reveal some serious differences in the materials.

  • dj_burkhardt

    Disappointing that the article just glossed over HED wheels. Rumor has it that Steve Hed refused to offer a consumer carbon clincher because of these exact issues – their Jet Black wheel line combines the best of a deep carbon wheel alongside best in industry braking.

    The new Vanquish series is a disk-carbon clincher, which seems to be the only truly safe way to ride hard on carbon clinchers.

    • James Huang

      Sorry, that definitely was not the intent! I spoke with Steve firsthand about this ages ago and yes, you’re correct. I’ll revise the caption to make my point more clear. HED’s position on the subject was obviously rare, and also extremely admirable given that he easily could have raked in a bunch more sales had he been willing to compromise his principles.

      On a related note, I have a review of HED’s Jet 6 Black aluminum/carbon clinchers coming shortly. Spoiler: they’re awesome.

      • dj_burkhardt

        Thanks James! Always a fan of your writing.

      • Jesse Nofziger

        @Jame@disqus_ZiZ7FkAYnw:disqus IIRC HED’s issue had always been that it was the tires themselves that couldn’t stand the high heat generated from braking, not necessarily the wheels. And in this video you do see a lot of tires blowing off the rim before the rim actually fails. This is a twofold problem – the tire can’t handle the heat, and at the same time, the rim can’t dissipate heat fast enough to keep the tire from overheating. Interesting that we hear wheel manufacturers talking about higher and higher Tg resins but not about the rim’s inherent ability to transfer heat faster. Maybe it’s time for an ‘ice-tech’ carbon rim :-)

        • tanhalt

          The tires are blowing off the rims because the rim is softening so much that the rim beads deform and can’t hold them in place.

  • Jonas/BETA

    Having worked at one of the bigger wheel brands, I had an insight on the problems with carbon clinchers. The main problem is that there is almost no Asian manufacturer that has useful testing equipment and standards for rim brake carbon rims, but still most of them offer such products. So it is no surprise that the best rims we tested were made inhouse by the respective brands. Also a lot of crap coming from the western world, just saying.
    The Alto testing protocol has a lot of flaws, starting with the 1200 W, which is really high (if my math is right, this means a rider of 80 kg keeps a speed of 36 km/h on a slope of 15%, using only one brake, and disregarding any aerodynamic drag). Then, measuring the pulling force at the lever does not mean you control the actual braking force, which then depends on the friction coefficient between pad and rim. Which also means that rim and pad combination indeed have an influence. Everyone who once had oily pads on a disc brake knows that the rotor goes blue, meaning more heat in the rotor. In my experience, newer Zipp rims are almost impossible to destroy by braking. Maybe Altos’ rims are 10 times better, but it is totally irrelevant.

    • James Huang

      Thanks for the comment, Jonas, and that’s an excellent point on the inconsistent braking force.

      Now where are we at with that fancy frame of yours? ;)

      • Jonas/BETA

        Nice you still remember that frame. Well, that project took a few unforeseen turns, but hopefully I can provide one to you next year. It got even fancier by the way: https://instagram.com/p/BaXxQlsDKrm/

    • Jonas/BETA

      A few more observations from the video:
      – the speed of the Alto wheel is the highest, meaning friction coefficient and therefore braking force are lowest. Also more convection which helps to cool the rim.
      – the speed at phase 2 is comparable to the other rims at phase 1, even though at the upper end of the range.
      – looking at the temperature curves, many rims are close to (theoretical) peak temperature when they fail. On the Alto rims, the temperature drops after about the same time where the other rims fail (this is normal, because the brake pads heat up). Adding more time is good for show, but does not mean much.
      – for some wheels, the weight is rocking up and down, creating unstable breaking force.

  • Stephen J Schilling

    when I bought my last bike, I make the conscious decision to throw money into wheels. And while I live in Zipp’s backyard, I wanted nothing to do with them or their carbon. Instead I have a 1550g pair of tubular, low profile Alu rims. And spent significantly under $2K. Technically, they are CX wheels.

    In return I have wheels that I have absolute confidence in.

    And inspite of smacking two major potholes with, only have a scuff on the brake track. I do not have the belief that any carbon rim would’ve been completely safe after that.

    Which brings me back to James’ main point: if I’m spend my own money on wheels, there really shouldn’t be an open debate on this. Not for the mass market.

    • pervertt

      Same here. I went for the best aloominum wheels I could get, placing more weight on safety and durability than shaving a few grams off the bike. Aero means nothing to me at the pace that I ride. Mind you, I like carbon, but there are a few places I would not have this material on my bike – the handlebars, the stem, the saddle rails and of course the said wheels.

  • Larry Theobald

    Thank you. Mille Grazie. Merci beaucoup, etc. etc. I admit to thinking carbon clinchers were a bad idea from the very start and suggesting (well, pretty much insisting) that our bike tour clients NOT use them on ANY of our tours in Italy. It reminded me of when titanium (a material not as strong as steel ,contrary to public opinion) was used in place of steel for square-taper BB spindles – with similar catastrophic failure. I wonder why the US Consumer Product Safety people (or other consumer testing entities worldwide) have not looked into this issue? Thanks again for having the guts to write and publish this, I’m sure you’ll get plenty of grief from both the makers and users. Something about the look of carbon fiber seems to overwhelm common sense while the public assumes if someone is making and selling these wheels, they must be 100% safe. Remember Spinergy Rev-X? I can remember working in a shop with clients who returned wheels which failed (luckily for them, not catastrophically) multiple times – only to insist on being given another pair. When I’d suggest that perhaps they should ask for a refund or sell off the wheels and use something that wouldn’t fail they were outraged!

  • MadBlack

    Thanks James, you have summarised why I have never touched a full carbon clincher in 20 years of their existence. People are way too gullible to marketing. Aluminium rimed wheels can easily be built to within grams of a carbon clincher and will provide braking performance under any condition. However, I’m looking forward to my first full carbon disc clincher on the next roadie.

    • Crash Bandicoot

      You’re better off with tubulars or alloy if you’re not racing, The biggest issue I’ve seen with CC’s is that if you get a flat at speed in a bunch its very easy to crack them while slowing down (note it will typically take longer to slow down in a group just because you’ve got to be aware of the rider behind you) this is a non issue on tubulars.

  • Tyler2017

    There’s so much wrong with this test, as many others have pointed out, that I’m not sure where to begin. So I’ll just start here:

    “What we didn’t want to do was have a different pad on every rim, because the data wouldn’t mean anything,”

    Ummm, what? Most manufactures design their rims specifically for certain pads, some even say that using other pads will void the warranty for the rims.
    So they’ve basically just proven that you shouldn’t use wheels in ways that void their warranties.

    Also, regarding the excuse about the test conditions being only meant to keep the video from being too long. First of all, time lapse photography. Second, I’m not a physicist, but wouldn’t a longer test at realistic, lower wattage potentially mean exponentially longer wheel durability? As in, wouldn’t the wheels then likely be able to dissipate heat at a rate that keeps them from failing at all? Leaves me wondering how much longer the long version of this would be.

    Also, don’t brakes in the real world actually slow the wheel down, eventually stopping it? Do anyone’s wheels keep spinning at the same speed regardless of time and force applied?

    Maybe I’m too cynical, but this test just seems like a marketing ploy.

    • Ryan Mason

      Seeing that we’re a co-sponsor (I’m one of the Co-Founders of Spark Wheel Works) I’ll comment on this. At the initial talks of starting this project, we shared the same concern over not using manufacturer’s specified brake pads, however the realization was that we needed to eliminate as many variables as possible and by introducing so many different pads, we’d have no significant information to provide. Ask yourself this, if you were directing the test, would you legitimately feel like any significant information would be attained by using the manufacturer’s spec’d pads? You’d have some failure data, but how could you translate it into significant information?

      It should also be noted that the pads used (SwissStop Black Prince) is considered one of the best performing pads on the market….and SwissStop manufacturers almost all of the OEM pads for the rims we used. So at the end of initial discussion, we agreed that this was the best approach to, at the very least, walk away with useable information.

      Secondly, the test wasn’t design to model real world conditions in the sense of increases/decreases of braking power, short segments of no braking, etc. It was designed to simplify variables to a point of understanding actual failure points under linear load and braking rates. There’s no reason why we can’t do another test with additional variables (forced cooling on the brake tracks, modulated brake forces, etc) but the manfuacturers of the rims we used as well as other manufacturers need to pony up for this test. We provided all the rims for this test to ensure there’d be no tampering of the rims from the manufacturers themselves. Yes, it’d be nice to test 10 rims from each MFG to confirm results but who’s going to pay for that?? It should be the MFG’s that are selling 1000’s of these rims per year.

      If you think this is a marketing ploy then take the next step and ask yourself what we and Alto have to gain from this “marketing ploy”? Either their rims are actually as safe from heat delamination as the test shows and riders who purchase wheels with the rims will have the comfort of knowing a manufacturer has done everything in their power to ensure the customer’s safety, or this was a marketing ploy and Alto is about to have massive amount of poor feedback on new rims, which I imagine will lead to immense distrust in their product design and implementation. Knowing Bobby first-hand, I’m willing to bet the latter option isn’t the case.

      • Ethan

        “however the realization was that we needed to eliminate as many variables as possible”

        But, the brake pad should not be considered a variable, it should be part of the wheel as that’s what the manufacturers intended. At the very least, if it’s not economically feasible to test and destroy another batch of wheels, test just a couple with their intended brake pads to show that the difference is minimal. It’s strange that you are so into real-world performance but neglected this pad issue.

        “ask yourself what we and Alto have to gain from this “marketing ploy””

        Alto and you guys get exposure e.g. from CyclingTips. I don’t really hear much about Alto, and have never heard of Spark Wheel, so this is great PR for you guys.

        • Ryan Mason

          The point of the test was to determine heat dissipation rate. There is no way to compare composite structural integrity unless the same pad is used on each test. If we did perform a test with supplied pads we could result in test that would look like this: open mold rim from ebay that comes with cork pads may last 10 minutes, and the ENVE rim with ENVE pads may last 8 minutes. Is the ebay rim of higher quality in terms of heat dissipation rate? Of course not. Everyone knows that. The cork simply causes less friction and less heat, but braking performance goes to absolute crap. If we standardized the cork pad to all rims including the ENVE, we’d expect the ENVE outlast the ebay rim tenfold. Thus, standardizing to a single pad distributed to all tests is required. Hope that helps clarify.

          Re. marketing, please understand where we’re coming from: for the cost of this project we could have spent our coin and time to produce five marketing driven videos that would likely derived much more positive feedback compared to this project, but our interest was generating data that, until now, hadn’t been generated. From the independent standpoint of a wheelbuilding house, we’re extremely thrilled with the results because it confirmed our hopes that the rims we supply on our custom wheels (four rims within the test) do very well in heat dissipation testing and certainly eek out off-the-shelf competitors on this heat dissipation rate test.

  • Jon

    Safety and, in a related sense, durability will always be relative measures (common sense would support a minimum standard should be imposed). Certainly, safety/durability will be used as differentiating factors by which products will be marketed. (As evidenced by the marketing video – note, I didn’t all it a documentary)

    As it pertains to your thesis – (20 years in…) I think you answered your own question.

    The industry has moved to disc brakes… (with respect to the vote being “out”, pragmatically, it seems not up for debate – are you aware of any manufacturers investing R&D dollars in refining the rim-brake paradigm?)

    More importantly, the industry would change if discs weren’t here and the “cost” – based on the actuarial analysis by their product liability guys/insurers – indicated loss of earnings due to product liability claims. Cycling isn’t an industry known for huge margins – I would imagine the potential to be whacked with a $30MM claim and the concurrent damage to one’s reputation would sufficient risk to catalyze change…

    In your research, did you learn what percentage of the wheels, in use, are estimated to be carbon, non-disc clinchers? And, of that percentage, how many users, in that cohort, will subject those wheels to the conditions that could result in a failure? Also, it would be interesting to know what the attorneys (product liability guys) think of the risk…

  • Vivre

    Does tire, and specifically bead, quality affect ability of the tire to remain attached to the rim in a (non catastrophic) failure? In my rather dull sensibility, using a high quality carbon rim mounted with a high quality tire and tube might reduce probabilities for detachment. What of using a tubeless-ready tire albeit with a tube? Would the bead shape of tubeless ready clincher make the combined components somewhat safer?

  • Crash Bandicoot

    I won’t get too much into detail on this because frankly James does a great job in the article but essentially this is a tragedy of greed and laziness. Instead of using carbon for Tubulars, and Disc brakes only the industry decided to get lazy and make a compromised product to gain market share. It was a smart move because nowadays you cant show up to a group ride without seeing carbon clinchers and the industry has somehow managed to pitch folks that if they don’t spend 1000+USD on a set of racing wheels they won’t be able to hang in a group ride. I race on Zipp 404 FC’s which are clinchers, luckily I live and race in a flat area. Personally my next wheels will be second hand tubulars from a cost perspective and safety perspective they seem like a much better buy and since I only use race wheels for racing ease of changing a flat is the least of my concerns. And yes I am still keeping up with group rides on my $150 alloy shimano training wheels.

  • Rob Arena

    Interesting that the FSE wheel failed at the lowest temperature in the group by a significant margin. This confirms my experience, I had two of their rear clincher wheels fail in a six month period. The Zipp wheels had a much higher temp failure and time to failure. I have several Zipp Firecrest models that have years of use and no issues at all at the brake track. FSE claim the failure was the result of operator error and refused to warranty. This test indicates otherwise.

  • Daryl Brice

    Run Disc brakes, problem solved. Your welcome.

    • Alex Croft

      Your grammar is as underdeveloped as disc technology for road bikes.

  • Richard Wittenberg

    This test is only ONE element of rim safety. You need heat resistance AND impact resistance to failure. You also need a rim bed which properly holds the spoke and stays together under over the long haul. It would be helpful to have this information alongside the melting failure information for a more complete analysis. Also, what is the point of using a testing protocol that does not represent what goes on in the real world? Using higher wattage over shorter time is not a substitute for lower wattage over longer time. Wheels do dissipate heat over this time so doubling the load is not a substitute at all for time.

    Do you have any data on the temperature at the brake track at failure? This is far more important than wattage at time.

    • Alto’s full-length video has all that data including the cool-down rate for each rim.

    • Larry Theobald

      All good points but the folks who did this test were mostly interested in proving the superiority of their product vs the others. I see nothing wrong with that. CPSC or someone like them should do the testing you describe and the wheels should pass the tests before being offered for sale. One thing I wonder about – did this test include other wheels that were equal to or superior to the Alto product and did they simply leave those results out? There are some major names in the carbon wheel biz missing here. How did they decide on the wheels to be tested?

      • Bobby Sweeting

        Hi Larry! I agree, there are some major brands that we would have loved to include. Mainly Shimano and Campy. Unfortunately, rims are very expensive! Spark Wheel Works provided all of the rims for this test, and we literally got as many as we could! It was limited by the vendors that they work with and the availability. If we can get our hands on any new rims from other major manufacturers then we would like to amend the video and repost it with more tests. The more information and data we can provide to the customer, the better.

  • Alex

    The Mavic C40s aren’t foolproof either. My buddy melted some on a descent and he isn’t exactly hefty at 160lbs. Good descender too.

  • Mondo Rodriguez

    Carbon Fiber is a joke…in my 35 years of riding everything from high end and low end Road Bikes, MTB, Backpacking MTB, Commuting, and BMX…yes, BMX to this day, watching carbon fiber failures and full fractures in my friends bike frames, handlebars, crank shafts, wheels and spokes has proven to me that CF is merely a novelty that has no place in most of the rigors of cycling. The constant inspection of such parts, and worrying and asking “does that look like a hairline?” makes my aluminum pinned and welded wheels, gusseted and welded frames, CroMo cranks and aluminum bits and pieces worth every single ounce over CF. Pedal Harder and Faster…

  • Keir

    With tubulars you have an excuse to abscond to the workshop to put on another layer of glue and enjoying a whisky from the workshop decanter while avoiding house duties. Or am I missing something?

  • Bmstar77

    What does 7lbs or 9lbs of force feel like at the lever? Is that like a constant -5% descent by a mid-weight rider keeping the bike at 20mph or so? Or is it more like a heavy rider on a -15% descent? And I’m not sure how the “135lb of radial load” translates to descending inertia. Maybe I’ve missed something. Either way, great test by Alto as it’s created a lot of discussion.

    • James Huang

      Unfortunately, the force at the lever doesn’t really tell you anything on its own about how much actual braking is happening. Alto’s test is interesting, but as others have noted, it’s not a true apples-to-apples comparison since the deceleration force isn’t held constant across all the wheels tested.

      But nevertheless, I agree that the test has been very good in terms of generating some much needed discussion. Carbon clinchers are a lot better than they used to be, but I still don’t have anywhere near universal confidence in them.

  • Adam K

    As heat is caused by friction – the rotation speed of each wheel on test would be good to know. I.e was the alto spinning at 5kmh faster as the rim itself is more slippery and thus generating less heat.

    Calls for a standardised test representative of a weight / gradient and time should definitely be introduced. I have a friend with a set of enve’s who is a strong guy and done 50,000km and they are like new. Another guy weighs 120kg and has blown up 2 by going down a very steep descent. At a certain weight – to me it is almost failing duty of care for a salesperson to sell a carbon clincher to such a rider

  • Geoff

    Realistically speaking, given the marginal gains associated with carbon rims, do carbon clinchers make sense? If you need the performance benefits offered by carbon rims, you are probably racing at a fairly high level, in which case you probably would be using tubulars anyhow, to get the marginal gains you need to win races. That raises the question then whether carbon clinchers aren’t still just a vanity product, aimed at gullible consumers with cash to blow?

    • jules

      carbon clinchers are handy for races you want to ride to

    • cnm

      Chad from Mavic here – I wont spend much time commenting on the test (at least here), but I would like to offer some input on this question. One of the reasons that full carbon clinchers exist is to meet the demand for aerodynamics. First, to achieve the best aero shapes with aluminum is quite difficult. Imagine the Zipp 454 NSW made from aluminum!? It’s probably not even feasible. Second, to make an aero wheel out of aluminum would be far outside of what cyclists would accept for weight. Even if you compare a full carbon clincher rim to a hybrid (alloy rim / carbon fairing) rim, at any depth, the carbon clincher will almost always be lighter. Not by a lot … but enough that those concerned by weight will demand the lighter option.

      Then, there’s the cache of full carbon. HED has a very nice hybrid option as do we in the Cosmic Pro Carbon Exalith. They are aero, reasonably light and have great braking. However, the demand for full carbon is such that these wheels are incredibly underrated.

      I hope this helps give some scope on the demand for full carbon clinchers. Happy to discuss further.

      • tanhalt

        Equivalent depth and aero performance carbon/aluminum hybrids and full carbon clinchers are typically within 10s of grams of each other and the hybrid solution has dramatically better braking…something many of the same folks who desire full-carbon clinchers see no problem adding the additional mass (and aero drag) of basically 400-500grams (total system increase) to obtain by asking for bikes with disc brakes. It really IS all about looks…oh, and it’s “cachet”, not “cache” ;-)

        • cnm

          Thanks for bringing back the painful memories of losing the spelling bee.

          • tanhalt

            Well, to be fair, they’re not English words, but French…then again, seeing as you work for a French company… (just pulling your chain).

            • cnm

              Oh putain …. ????

        • Ryan Mason

          Could you elaborate on which models you’re comparing in your statement, “Equivalent depth and aero performance carbon/aluminum hybrids and full carbon clinchers are typically within 10s of grams of each other”? In our analysis, this is incorrect. Take for example, the Mavic Cosmic Pro Carbon Exalith compared to the Cosmic Pro Carbon SL UST, which are essentially the exact same wheelset save for the carbon hybrid versus full carbon rim band. The latter model is close to half a pound lighter. My point is that it’s almost 200 grams lighter, which is 20 times more than your statement claims. You can also compare the ENVE SES 4.5 wheel set which is both wider and deeper than the aforementioned hybrid wheel set, and you’ll find the ENVE is 100 grams lighter. While you may not care to acknowledge this as an important difference, there are plenty of riders that we interact with on a daily basis that do, and to brush their interests aside as ill-informed or irrelevant seems to miss the entire point of our test.

          • tanhalt

            How about Zipp 404 Firecrest clinchers = 1723g (claimed) vs. Hed Jet 6 Black = 1673g (claimed). Enve 4.5 = 1526g (claimed) w/DT240 hubs, but the front is only 48mm deep and the rear only 56mm deep, both of which are significantly less deep than the 60mm of the HEDs and the 58mm of the 404s, so it’s not really a fair comparison to that.

            Looks like the hybrid construction actually “won” the weight battle in the comparison between the Jet 6 and the Firecrest 404s…not to mention there is data out there showing they are most likely faster aerodynamicaly as well. Not all hybrid constructions are equal, obviously ;-)

      • Ryan Mason

        @c@disqus_U25ZXK2jpR:disqus Please see my comments below regarding the hybrid carbon vs full carbon comparison. The majority of riders we interact with feel that the 200 gram exchange is enormous given the amount of money they’re investing in their wheels, and thus, if they can find a carbon clincher in which they can learn to brake responsibly, provides lighter rotational weight, and is also stiffer than the hybrid carbon option (so far, no one has mentioned lateral stiffness comparision between hybrid carbon and full carbon wheels) they see no reason to consider the hybrid carbon. In our opinion (that is, the opinion of Spark Wheel Works), Mavic and ENVE did very well on this test and we were hoping for these results from both brands (epsecially ENVE).

    • Based on my experience in the biz for 3+ decades, I believe your last sentence pretty well sums it up. YES is the answer to all three charges.

      • cnm

        @larrytheobald:disqus – please see my comment below … there are plenty of people who do not fall into any of those three categories. They are people who are looking for an aero advantage in a lightweight package. Only realistic way to achieve that is with carbon. And in terms of “who” this customer is … it wouldn’t be fair to make a blanket statement that they are vain, gullible and frivolous with their money. What’s wrong with people who enjoy spending money on something that they really enjoy? Is it the same story with the person who buys an expensive car, or a boat or a nice watch? Maybe a nice suit? Or perhaps an expensive cycling trip? People “nerd out” on things and there’s no fault that should be pointed at someone for wanting to buy carbon clinchers. …. IMHO.

        • Since you’re a guy who derives an income from selling these things, I’m going to suggest you might lack an objective viewpoint on this subject? While we do enjoy support from “official suppliers” none of them expect me to be a corporate shill who blindly endorses everything they make or has a problem if I suggest clients NOT use a certain product during their time with us in Italy. My comments and suggestions are all based on experience rather than whose name is on the check.

          • cnm

            @larrytheobald:disqus – no problem Larry, I respect your opinion and only offer an alternative viewpoint. My points were my own and not those of someone (corporate shill !? come on…) who is deriving income from selling “these things”. I had carbon clinchers before I started working at Mavic so that’s pretty objective !! Happy riding !!

  • Durianrider Vegano

    Want to see what happens when a carbon rim fails at high speed mountain pass?

    See if you can spot who had alloy rims on that day and who was running carbon.

    • cnm

      @durianridervegano:disqus – that crash had nothing at all to do with carbon wheels … Matt Brammeier, the rider in the crash, said he was taking too many risks trying to bridge to the leaders and had a bad line into the corner and was out of control … an unfortunate rider error.

  • RobertW

    Looking at the test, it appears that Alto lasted the longest on account of it having the lowest friction, thus the worst braking. In the real world one would be obliged to squeeze the lever harder to stop and explode them at the same time as all the others.

    • jules

      no, all tests applied 1200w load. that’s the braking force. if it had lower friction, it wouldn’t have held the 1200w load.

      • James Huang

        That 1200W is the input load and does not indicate how much braking is going on. In effect, what we have here is the same rider on the same descent, but decelerating at different rates.

        We dive into this in the latest podcast, which should be posted today or tomorrow.

        • Bobby Sweeting

          The energy input into each rim is the same, as it comes to an equilibrium at 1200 Watts. This includes the motor input, caliper force, coefficient of friction, and kinetic energy of the wheel.

          All of the rims ran within 1.5mph of each other and (in the case of Alto in phase 2) with a 2lb lever force variance. With an average adult being able to grip at 100lbs, this essentially means that all of the rims have about the same stopping power. You wouldn’t notice a 2-5lb difference in pull strength in the field in order to modulate power during braking, so it’s inconsequential. I hope that clears things up a bit!

    • cnm

      @disqus_Q6QtMuQzkT:disqus – Hi Robert, Chad from Mavic here. You nailed it on the head. One of the biggest flaws of this test is that the variables do not control / account for the brake track texture and, as the Alto has none, they have a big advantage in this scenario.

      • Bobby Sweeting

        Hey Chad! Just to clarify, none of the rims are textured except for the Zipp, Enve, and Mavic. If the energy input into each rim is identical and the speed is variable and displayed, I’m curious to know why you believe the test is flawed. Especially considering the Alto phase 2 test, where it ran slower and with more friction than others but still without failure.

        • cnm

          @bobbysweeting:disqus- Hi Bobby. I don’t want to get into a big discussion here, but our thoughts about the test will soon come via various outlets. We also had a chance to talk about carbon clincher safety outside of this “test” – hopefully that will be valuable for everyone. What I will say here, and everyone can take this for as they wish, is that our engineers (both product and testing) came with the same feedback (independently) as nearly half of the brands which were tested. We aren’t saying the efforts weren’t noble … but, in (not just our) opinion, there are too many things that are peculiar, or “off”, about the test to make it credible and useful for anyone who is considering carbon clinchers.

          • Bobby Sweeting

            We certainly don’t need to get into a discussion, but I’m very curious to know what issues you guys could have with a test that has literally followed the scientific method to a T in order to gain a direct comparison between composites properties. For the record, the only brand that has reached out to me so far has been Knight. They approved of the test protocol for the most part, they simply wanted their rim back for inspection.

            I also encourage any brand that has an issue with the test to bring an Alto rim to their facility, test it on their own jig (with any carbon brake pad, it won’t matter) and publish the results for the world to see. As far as I can tell, Alto has been the only brand to actually publish the results of a heat transfer comparison test, as opposed to just talking about it. It is easy for competing brands to say “the test is flawed, our rims are great,” but I hope that we will inspire them to prove it.

            • cnm

              @bobbysweeting:disqus – what I encourage, if you’re keen, is to have a discussion about this offline and we can share with you not only our feedback on your test … but also how we perform our tests. You would be welcome to adapt your test to include our methods / recommendations if you agree with our points. Then, you could rerun your test with all of the same wheels to see the results – we would even offer ours to you at no cost. Alternatively, we would offer to put your wheels on our bench and, if you agree, we can publish the results. We’re open to the collaboration and our ultimate goal is to achieve 100% consumer confidence in carbon clinchers.

              • Bobby Sweeting

                I totally agree. It cost Spark a fortune to get all of the rims for this test, but it was the only option at the time. If every manufacturer would agree to discuss the test protocol and submit a rim to be published, I think that would be excellent. Please feel free to write us on the contact page of our website, and it will come straight to me. Our ideal scenario would to have a few rims from each brand in order to operate the test a few different ways, in order to measure different variables. But it can be tough to talk companies into supplying free test rims, as I’m sure you know. I appreciate your willingness to be open with the public about your testing and results!

  • by7

    my worst experience was a carbon clincher which lasted literally 4km of a twisting descent…it was brand new , cork pads. After 4k downhill it was already delaminating and I had to open the braks and crawl back home using only the rear brake. replaced by manufacturer under warranty.
    I have probably gone through 4-5 delaminated rims (or somehow deformed). It is enough to get stuck behind a bus in a narrow twisting road and you are at risk of failure…
    Now I keep:
    – Bora Clincher for rolling courses and general use
    – Campagnolo Shamal for serious mountain courses where I do not want to take risks
    – Carbon tubs for special occasion and more predictable mountain courses

  • Brian Racerhead


    I had a catastrophic failure on a Reynolds Wheel,while racing the Race across America, while going down the “glass elevator”. At 45-50 mph, the front wheel failed, fortunately I was able to stop without injury. Without overstating it, I could have died. Please see their response below.

    “I apologize for the delay in response we’ve been a little short staffed lately, I understand your circumstance, however, I want to be clear that this is NOT a manufacturer defect. This is caused by overheating the brake track causing the resin to change forms.

    Web: http://www.reynoldscycling.com

    9091 Sandy Parkway,

    Sandy, UT. USA 84070


    My question is, If the “cycling press” has been aware of this issue for 20 years; why hasn’t there been more written about this issue?

  • David Walker

    I think that most everyone is completely missing the boat in their complaints about the Alto tests and are asking the wrong questions. James as well. I have seen complaints about not using the manufacturer’s recommended brake pads, different braking surfaces, etc.. All of that is completely irrelevant to the test and does not invalidate the test. For the test Alto put 1200W into the drive motor and a fixed 7 pounds on the brake lever. The different wheels then rotated at constant, and different, speeds until they failed. What that means is that EVERY rim had 1200W of heat applied to it. Regardless of pad or braking surface. The varying wheel speeds are the result of the different braking surfaces, etc.. However, that does not change the fact that with the SAME amount of heat input to the wheel the various wheels ended up at different temperatures. And most of the wheels failed at that amount of heat input. All well and good and perfectly valid. However, the important question, that nobody seems to be asking, is if 1200W is a reasonable power input or not? For a quick calculation a rider+bike that has a mass of 80kg traveling at 50km/hr dissipates 771W in braking to a stop in 10 seconds. The same 80kg rider+bike descending at 100 meters/minute while traveling at 50 km/hr (12% grade) dissipates an AVERAGE 400 W of braking power to maintain a constant speed once aerodynamic drag is subtracted. So, the 1200W chosen is high by 2 or 3 times typical braking loads. And probably do not represent what happens in the real world. I think that the flaw in their logic is that they said that they turned up the power to reduce the time to failure. However, that is not a reasonable approach because at a given braking power each of the wheels will reach some steady state temperature. If that temperature is below the critical temperature for the resin then the wheel can withstand that temperature FOREVER without failure. The lifetime to failure at different temperatures is very nonlinear. If a wheel can maintain a safe temperature at normal braking loads then its behavior a braking loads 3 times that amount is pretty much irrelevant. Since the wheel never sees that in real life. So, the correct way to so the test is to apply a typical braking load at looking at steady state temperature and time to failure.

    • Bobby Sweeting

      David, this is the most spot on analysis that we have read on the internet thus far!

      You are correct about the energy input to each rim, and that is what frustrated me about the recent podcast with the Enve and Mavic engineers. They claim that by increasing mu (coeff of friction) at the rim, there is more energy input to the rim. You can’t create energy! Even if mu is increased, the angular velocity of the rim will decrease until you reach equilibrium at 1200W. These speeds were displayed for full transparency. So the amount of energy into each rim is identical, and the amount then conducted and converted to heat relates solely to the properties of the composite and resin.

      You are also right about the 1200W input! We do not test our prototype rims with this standard, we use an interval test that more accurately simulates a descent in the real world. However, in order to get an accurate and easily understood composites comparison, we chose to create a destruction test. The factor of safety from this test can then be extrapolated over many years of use. What I mean by that is this: you are VERY unlikely to get a new set of wheels and run the brakes on day one until the rims fail. However, you are likely to reach the glass temperature of those rims multiple times per week, for just a few seconds at at time. Like any material, the resin will begin to break down over time from cyclical loading. The rim may develop a bulge, and eventually fail if it isn’t caught. With this test, we wanted to show when and how rims failed, and create a metric that would be directly proportional to long term durability due to resin stability and Tg. Nothing more, nothing less. We would have to test with a different protocol and with brand specific pads if we wanted to see real world heating and cooling curves, but that’s a test for another day!

      Thank you for the excellent input, you clearly understand the physics here at an intricate level.

      • David Walker

        I’m not a composites engineer so the question I have is what is the long term effect of occasionally going above Tg? I can imagine two scenarios- 1) the epoxy gets a little softer and then, provided the duration is such that delamination doesn’t occur, it gets harder again as it cools and there is basically no long-term effect, or 2) the epoxy gets softer and then when it cools and hardens again it ends up slightly different structurally than it was before and has cumulative damage over time. I don’t know which is true. Also, even if the second case were true, if it takes 25 years to fail then it doesn’t matter nearly as much.

        • Bobby Sweeting

          That is a great question. Resin (once cured) responds to heat and structural loading just like any thermoset or plastic. Once it’s heated and loaded (by the tire), it loses some capacity to resist stress as it’s tensile strain becomes compromised. This is why carbon clincher failure is still an issue at most bike shops. It isn’t instantaneous failure after one use, but slow delamination over a period of a few years. Our goal for this new rim project was to develop a resin that wouldn’t be effected by this heat fatigue, because the conductive properties were such that you would never be able to reach the resin glass temp in the first place. It’s been a fun (and very long) process!

December 15, 2017
December 14, 2017
December 13, 2017
December 12, 2017