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by James Huang
May 9, 2018
Photography by James Huang
TECH NEWS BROUGHT TO YOU BY BIKEEXCHANGE
The Canyon Aeroad CF SLX is widely regarded as one of the top aero road bikes on the market, and the company recently expanded the model’s capabilities by adding disc-brake versions last year. In another truly long-term test, CyclingTips US technical editor James Huang has spent more than a year on a mid-range 8.0 Di2 model to see if the new configuration has tempered the bike’s appeal — and if any issues have appeared over time.
In short, the Aeroad CF SLX Disc loses a bit of the magic of the standard rim-brake version, but it’s still a superb aero road bike, and an incredible value, too.
Canyon debuted the first-generation Aeroad CF in May 2010, and I remember the launch event well. It was held in Italy at Il Borghetto di Andrea Tafi, a tiny cluster of vacation-getaway apartments tucked in the picturesque Tuscan landscape, and run by the famed Italian cyclist. The setting was beautiful, and the riding was fantastic.
I also remember being somewhat underwhelmed by what Canyon had presented.
Despite this taking place nearly eight years ago, the aero road bike category was already becoming fiercely competitive. Scott was arguably leading the way with its groundbreaking Foil, one of the first to use the then-revolutionary Kamm-tail truncated-airfoil tube shapes that would become so prolific in later years.
The Canyon Aeroad is one of my favorite aero road bikes, and the new disc version does nothing to temper that sentiment.
Canyon took a more conventional and intuitive approach with the original Aeroad CF, focusing on reducing frontal area and minimizing abrupt shape transitions on the molded carbon fiber frame (similar to the Felt AR and Cervélo SLC-SL of the era).
The company hadn’t done any wind tunnel testing at the time, and the only drag tests performed were all simulated using computational fluid dynamics software. Even so, no specific aerodynamic data was offered at the time.
Although the bike was comfortable and handled well, the skinny tubes left it feeling soft and vague under power. And without any hard data to support Canyon’s murky claims, it was unclear if the Aeroad CF was particularly aero at all.
Canyon clearly learned the mistakes of its half-baked first attempt, as demonstrated by the introduction of the second-generation Aeroad CF SLX in July 2014. While the original Aeroad CF felt like a middling attempt to keep the big boys within sight, the new machine instantly thrust Canyon to the forefront.
The frame shape is visually striking, but also effective in terms of reducing aerodynamic drag, based on independent third-party testing.
This new model was not only truly aero — and one of the best in that arena, according to independent third-party testing by Tour Magazin — but its modern Kamm-tail tube shapes also greatly improved the overall frame stiffness thanks to their dramatically wider cross-sections. It was noticeably more solid up front when sprinting or climbing out of the saddle, and the newly bolstered down tube, bottom bracket area, and chainstays yielded far-snappier reflexes when you put down the power.
Even better, Canyon managed to do all of that while still maintaining a decent chunk of the original version’s excellent ride quality. Add in the remarkably attainable pricing of Canyon’s direct-to-consumer business model, and it’s easy to see why the current Aeroad CF SLX has been so successful (you can see our review of that version here).
Canyon updated the Aeroad CF SLX yet again last year, this time with disc-brake versions for riders that desired better stopping performance (myself included). And so it was that I took delivery of an Aeroad CF SLX Disc 8.0 Di2 long-term test sample, equipped with Shimano’s Ultegra Di2 groupset, Reynolds Strike deep-section carbon clincher wheels, Canyon’s usual H11 Aerocockpit CF integrated carbon fiber aero handlebar-and-stem combo, and a Fizik Arione saddle.
Actual weight, without pedals, was 7.70kg (16.98lb) for a larger-than-it-sounds size XS.
I’ve spent a lot of time on the rim-brake Aeroad CF SLX in the past, and am quite fond of that bike’s performance characteristics. Much to my relief, nearly everything I enjoyed about the rim-brake version of the Aeroad CF SLX carries through to the disc-brake edition.
No review of an aero road bike would be complete without discussing its aerodynamic performance, of course, and while aerodynamic efficiency is always difficult to ascertain from the saddle, especially at more moderate speeds, there is nevertheless a tangible difference between the Aeroad and a modern round-tubed bike as the speedometer needle rotates further clockwise.
The flat-back profile of the seatpost not only helps with aerodynamic efficiency, but also with rider comfort.
Simply put, the Aeroad CF SLX Disc is a joy to ride at higher speeds, and it’s quantitatively easier to maintain a brisk pace — as is always the case with aerodynamics, the faster you go, the more advantage you get.
Part of the credit surely goes to the sleek design of the bike itself, but the way it aggressively positions its rider obviously plays a major role as well. The stack is low and the reach is long, just as it should be for a bike like this, although only more flexible riders will be able to fully take advantage of what the Aeroad CF SLX Disc has to offer.
Either way, high-speed cruising is definitely the Aeroad CF SLX’s strong suit, not a lightning-quick jump off the line. Like the rim-brake Aeroad CF SLX, the disc-brake version is substantially stiffer and feels more efficient than the original Aeroad CF, but overall rigidity still isn’t on par with Canyon’s Ultimate CF SLX, or any other top competitor that focuses on stiffness over aerodynamics.
The Aeroad CF SLX hardly feels soft, but blistering acceleration isn’t one the traits that I would associate with it. And before anyone casts aspersions with tales of Canyon-sponsored riders Luca Paolini or Alexander Kristoff successfully sprinting for the line aboard an Aeroad, keep in mind that structural efficiency matters, but at the speeds those guys travel, low drag matters more.
The Aeroad CF SLX Disc is a natural climber regardless, especially with the versatile 52/36T chainrings and 11-28T cassette that Canyon provides stock with each one. The relatively low weight helps in this regard, as does the very good chassis stiffness.
Also helping with out-of-saddle climbing (and sprinting) in particular is the one-piece integrated carbon fiber cockpit, which is stunningly rigid; combined with the straight 1 1/4″-diameter steerer tube, it provides a very direct connection with the front wheel when you’re pivoting back and forth, even as the rest of the bike occasionally wags a bit behind it.
Visually, the Canyon Aeroad CF SLX is arguably one of the best-looking aero road bike options out there.
It’s once you crest the top of the climb and start rocketing down the other side that this new disc-equipped version can really spread its wings. The direct-mount version of Shimano’s Dura-Ace rim-brake calipers are about as good as it gets, with very good power, excellent lever feel, and great control. But it still can’t compare with what even Shimano’s Ultegra-level hydraulic disc brakes offer on the road, especially in wet conditions and when using carbon rims. There’s a weight penalty for sure, and were I still living in the flatter Midwestern area of the United States, I likely wouldn’t feel compelled to go this route. But I live in Colorado, where descents can last 20 minutes, and I’ll happily lug a couple hundred extra grams uphill if it makes for a faster and more controlled flight back into town.
Handling is expectedly quick, with the sub-meter wheelbase and tidy 415mm-long chainstays making the Aeroad eager to change direction. Some might even dub it twitchy, but it’s certainly appropriate for the segment. Don’t forget Canyon uses its most aggressive fit geometry here, so it’s clear what the Aeroad was designed to do. This is a bike that looks fast because it was meant to actually go fast; it doesn’t just play the part on the showroom floor, and then let its rider sit upright like a sail in the wind.
The geometry of bike handling
Comfort-wise, the disc edition of the Aeroad CF SLX is a bit of a mixed bag. I was always impressed by how composed the rim-brake Aeroad CF SLX rode. It wasn’t exactly cushy, but it was far more planted and smooth than appearances would suggest, even with the skinny 23mm-wide Mavic tires (and 13mm internal-width rims) that came stock.
Canyon has since gone more progressive, using 17mm-wide Reynolds Strike carbon clinchers here and a staggered 23/25mm front/rear Continental Grand Prix 4000s II setup here. But even with the increased air volume, something was amiss.
The rear end of the Aeroad CF SLX Disc felt pleasantly familiar, soaking up road buzz and doing a decent job of attenuating bigger impacts thanks to the D-shaped seatpost, the matching D-shaped seat tube, and the lowered seat stays, all of which have been shown to improve rider comfort by allowing for more flex than similarly sized round tubes and a conventionally configured seat cluster. Whatever reinforcing Canyon may have done to the Aeroad CF SLX Disc’s rear triangle doesn’t seem to have made any impact on how the frame feels on the road.
But it’s a different story up front.
The fork crown blends in nicely with the frame.
This new disc-brake fork is necessarily beefed up relative to the rim-brake Aeroad CF SLX version, and the ride comfort seems to suffer as a result. Compounding the issue is the integrated cockpit; it’s a gem when muscling the front end around, but combined with the rougher-riding fork, it transmits every bit of road texture to your hands, for better or worse. It also doesn’t help that the bars are only partially wrapped up top. The shape may be comfy, but there’s still no replacement for a layer of cushy foam, and the stepped surface of the H11 Aerocockpit CF that clearly demarcates where the tape should end isn’t entirely conducive to wrapping further inward.
Componentry-wise, there’s not much point in here discussing the ins and outs of the Shimano Ultegra Di2 groupset my test sample arrived with, seeing as how it’s now been replaced with the newer Ultegra Di2 generation in the time this long-term test has been conducted. But Canyon has carried on with the Reynolds Strike carbon clinchers, and like the Aeroad CF SLX Disc’s ride quality, my opinion on those is a little mixed.
The Reynolds Strike carbon clinchers certainly feel fast, but despite claims to the contrary, I also found them to be more susceptible to crosswinds than I would prefer.
The blunt, 62mm-deep profile feels fast in a straight line, but even with Reynolds’ fancy “Swirl Lip Generator” ridges straddling the spoke holes, it still feels more susceptible to crosswinds than I’d prefer. Canyon is clearly open to progressive thinking when it comes to spec, as evidenced by the staggered tire sizes, but there are merits to doing the same with rim depth.
Reynolds already supplements the the 62mm-deep Strike with the 41mm-deep Assault, and it seems like this would make for a versatile combination that would still be fast, but also more manageable in a wider range of conditions. Much of the appeal with buying a Canyon is the comparatively low pricing, after all, so it seems logical that a Canyon buyer may not be all that interested in buying a fleet of aero wheels to suit the day at hand.
This is subjective, of course, but I also don’t feel the hubs befit the sleek look of the rims. They’ve held up fine over the past year, and the rear hub has a reasonably quick 10-degree engagement speed on the conventional pawl-type ratchet mechanism, but visually, they’re disappointingly bulky and lumpy.
One key advantage of the disc version of Canyon’s aero road machine is the increased tire clearance, and there’s heaps of it on tap. The narrowest pinch point, in between the chainstays, measures nearly 40mm across — more than enough room. Given that, I quickly decided to swap the stock wheel-and-tire setup in favor of Enve’s superb AR Disc 4.5 and 28mm-wide Specialized S-Works Tubeless clinchers (which puff up to nearly 31mm on those ultra-wide rims). The effect on ride quality was unquestionably positive, and if Enve’s aero data is to be believed, they’re just as speedy. Even better, I dropped roughly 200g of weight in the process.
The deep-drop, classic-style bend fosters a long-and-low position.
Needless to say, once the Enves went on, they didn’t come off.
Unfortunately, the Reynolds wheels’ 25mm-wide external width precludes going with anything wider than a 25mm-wide tire to match (lest you mess up the aerodynamics). Canyon has stuck with the Strikes and the 23/25mm staggered tire setup for the current model year, but unless your roads are absolutely pristine, I’d advise at least switching the front tire to save your hands.
JRA with the Angry Asian: Does frame compliance still matter?
It’s often the details that don’t garner attention until you’ve really had a chance to spend time with a bike, and Canyon deserves plenty of accolades for what it’s done with the Aeroad CF SLX Disc.
There’s been no creaking from the wedge-type internal seatpost binder, nor a peep from the PF86 press-fit bottom bracket shell, despite plenty of washings. But I’d still like to see Canyon include some sort of rubber cover to help prevent water from sneaking into the frame around the post. There’s a decent-sized hole at the bottom of the frame to let that water escape, but I’d prefer it didn’t get in there in the first place.
The internally routed rear brake hose never rattled inside the down tube, either. That’s because Canyon stealthily equips the down tube of Aeroad CF SLX Disc frame with a small zip-tie anchor that securely holds the hose up against the inside of the down tube. It’s a bit tricky to replace, but only if you’re not familiar with the prescribed process, and truth be told, the electronic transmission and hydraulic brake lines mean you’ll likely never have to dig around inside the frame tubes, anyway. The plug is basically invisible when a bottle cage is mounted, too. It’s an ingeniously simple — and effective — solution.
Routing rear disc-brake hoses through the down tube makes for a clean appearance, but it can also result in annoying rattling. Canyon does away with that by cleverly incorporating a zip-tie that tightly pulls the hose up against the inside of the tube. It’s a smidgeon of practical genius.
Also residing inside the down tube, down near the bottom bracket, is the Shimano Di2 battery, which is held in place with a snug-fitting plastic bracket. It’d be a pain to replace the battery if it’s ever required, but Shimano’s enviable track record with battery reliability and longevity means it’s unlikely you’d ever have to.
A small pocket on the underside of the integrated cockpit tucks the Di2 junction box up and out of the way, eliminating any unsightly zip-ties, but leaving the LED indicator and function button readily accessible. The plastic tab that holds the box in place is flexible enough that you can pop the box out to access the charge port, too (although users should still exercise caution to prevent cracking the plastic).
That integrated cockpit creates complications when attaching accessories, too. Canyon does offer (as an optional accessory) a tidy custom bolt-on mount for Garmin and SRM computers, but other brands aren’t officially supported, nor is there any good way of attaching a forward-facing LED blinker if you’re so inclined.
Canyon offers the H11 integrated carbon fiber cockpit in multiple sizes, but buyers unfortunately can’t select a specific size when ordering the bike.
Those issues pale in comparison with the fact that Canyon doesn’t allow Aeroad buyers to select cockpit size when ordering — a potentially major complication given the non-standard setup. I generally run a stem that’s longer than usual for my preferred frame size, for example, and while Canyon was able to supply me with a longer Aerocockpit than what is normally supplied with an extra-small Aeroad, regular buyers wouldn’t enjoy the same luxury.
Length-and-width options are limited, too. In my ideal world, I would have run a 120mm-long stem and 410mm-wide Aerocockpit, but Canyon only offers that length with a 430mm-wide bar.
It’s apparently possible to swap size after the fact, but doing so is hardly convenient, nor can you wander into your local Canyon dealer to facilitate the process (although the pain is lessened somewhat by the exposed cabling up front). Then again, for this price, I suppose some buyers might be willing to make some concessions.
Canyon’s first-generation Aeroad was a half-baked attempt at the category. The current Aeroad CF SLX is anything but.
The minimal branding is much appreciated.
Canyon utilizes Kamm-tail tube shaping on the current-generation Aeroad CF SLX, and highlights the cross-sections’ flat backs with contrasting paint.
The flared intersection between the seat tube and seatstays seems to divert air around the upper section of the rear wheel.
Without a rim-brake caliper in place here, the seatstay area looks particularly clean.
The Kamm-tail theme even runs through to the headset spacers and top cap.
The PF86 press-fit bottom bracket will undoubtedly put some people off, but as far as non-threaded formats go, this is one of the better ones. Notably, it remained creak-free throughout a year of testing.
The head tube and fork crown combine for an elegant frontal profile.
The integrated wedge-type seatpost binder holds tight, and also stayed silent throughout testing. That said, it’d be nice if Canyon included some sort of cover here to prevent water intrusion.
The partially external cable routing doesn’t look as neat as fully-internal setups like on the Trek Madone, Giant Propel, and Specialized Venge ViAS. But whatever negative impact it has on aerodynamic performance will likely be more than offset for most riders by the ease of service.
Canyon provides two sets of water bottle mounting holes on the down tube depending on your particular needs. For single-bottle users, the lower position supposedly makes for better aerodynamics.
The ends of the thru-axle dropouts are capped for a finished appearance.
The rear dropout is capped as well.
While I wouldn’t characterize the Canyon Aeroad CF SLX frame as a couch, it’s surprisingly comfortable for what it is.
Proprietary seatposts are becoming more common on aero frames. The lack of choices is a little disappointing, but the stock version thankfully works well enough that most riders won’t have any reason to complain.
The slim top tube doesn’t make for earth-shattering torsional stiffness, but it’ll suffice for most riders.
The elegant shaping masks the oversized dimensions of the chainstays.
Tire clearance is generous all around. The stock 23mm-wide tires are shown here, but 28mm-wide tires fit just fine.
There’s heaps of daylight between the 25mm-wide rear tire and the seatstays.
Even down here, there’s quite a lot of room. Actual width between the chainstays is nearly 40mm.
Every Aeroad CF SLX is equipped with Canyon’s H11 Aerocockpit CF integrated bar-and-stem. Unlike some other aero handlebars, this one is actually fairly comfortable to hold up top.
The included headset spacers are profiled to match. A separate locking collar secures the headset adjustment so that subsequent bar height changes don’t affect bearing preload.
The stepped outer skin of the H11 Aerocockpit CF makes it clear that Canyon only intends for riders to partially tape the tops. That’s a bit of a bummer, though. The shape of the tops is surprisingly comfortable, but the grip is certainly more secure with a full tape job.
Flat-mount disc-brake calipers are used at both ends.
Interestingly, Canyon equips the Aeroad CF SLX with 160mm-diameter rotors front and rear, instead of a staggered 160/140mm setup, which arguably makes more sense.
The mounting bolts for the rear brake caliper are recessed up into the chainstay for a cleaner appearance.
Hidden inside the base of the down tube is a holder for the Shimano Di2 battery.
The Canyon H11 Aerocockpit CF includes a small pocket on the underside for a Shimano Di2 junction box. The placement leaves the button easily accessible, but you still have to remove the center cover and pull the junction box out to plug in a charger. Canyon uses the same two holes for an optional computer mount, with versions available to fit Garmin and SRM computers; no other computer brands are officially supported.
The press-fit bottom bracket will undoubtedly turn some riders off, but the fact of the matter is that it provides more room than a conventional threaded shell. Canyon makes good use of that additional real estate, too, equipping the Aeroad CF SLX Disc frame with chainstays that are ultra-fat, but yet still provide impressive tire clearance.
The DT Swiss thru-axles have removable levers that easily snap into place. As a result…
… just one lever can be used to undo both wheels, or you can opt to leave it at home entirely for a cleaner look (provided you make sure you have a multi-tool on hand in case of a flat).
The cradle hardware on the proprietary seatpost can be reversed for less offset if needed.
These hose connectors, supplied by Shimano, greatly speed up bike assembly since the two halves of the system can be individually pre-bled, and then screwed together for an airtight fit. However, they’re also unfortunately ugly.
Canyon choose the stock tires for the Aeroad CF SLX Disc more for speed than versatility, with a narrow 23mm one up front…
…and a slightly wider 25mm one out back. It’s a smart combo if speed is your primary concern, but it also limits the Aeroad CF SLX Disc’s utility to paved roads in good condition. I ended up swapping to wider tires early on in the test process, along with wider wheels to match, since the Strike’s 25mm outer width precludes the use of higher-volume tires without adversely affecting aerodynamic performance.
I also wasn’t a fan of the bulky-looking hub shells, which, to me, don’t seem fitting with the aero theme.
Unlike higher-end Reynolds wheels that use Industry Nine hub internals, the Strikes use more generic units produced overseas.
Reynolds says the Swirl Lip Generator — the small ridge that runs on either side of the spokes — reduces drag and improves stability in crosswinds. Does it work? It’s hard to say.
Current Canyon Aeroad CF SLX Disc 8.0 Di2 models now come with Shimano’s updated Ultegra groupset, not the previous-generation stuff shown on this long-term test sample. Either way, though, the frame is fitted with a metal plate on the side of the chainstay to protect against chain suck.
The suede-like bar tape is grippy and relatively cushy. The ends are secured with nifty caps that expand outward as they’re pushed into the bar for an extra-tight hold.