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November 24, 2017
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  • Steve G

    If it doesn’t feel right, just buy a new bike.
    That’s always the answer, right?

    • Chuck

      Even if it does feel right , buy a new bike ;) n+1

  • jules

    stay tuned for the next article in our series on stems.. the effects on handing of slamming your stem

    • Nathan Hosking

      Great article, as I just slammed the stem on my ‘event’ bike and found I was too bunched up in the traps with a 90mm stem – changed to 100mm and found I’m much more relaxed in the shoulders/neck at the end of an intense 1hr crit.

  • Mark_Kelly

    You left out chainstay length. I know that sounds bizarre, but I have seen many cases where people with very long stems needed them because their chainstays were too short. You touched on this in the comment about weight distribution but did not elaborate.

    At the other end of the spectrum, if the stem is very short it is often because the wheels are too big, the answer can be as simple as 650B.

  • velocite

    The major factors in bike stability as I see it are wheelbase and trail. Weight distribution needs consideration also, but the primary determinant of that will be wheelbase. I agree with the Tom Kellog’s remark to the effect that a short stem -> steering wheel and long stem -> tiller, but not that a short stem results in ‘twitchiness’. Surely twitchiness relates to stability and therefore principally to wheelbase and trail – not to stem length.

    The stem length on my road bike is 100mm, which I suppose is ‘medium’, and the weight distribution is 59% rear 41% front. I could shift more weight to the front by fitting a longer stem, but I would need to get a shorter frame to keep the reach right. At this time I can’t think of why I would want to do that – unless I wanted to experience more of a tiller than a steering wheel. I would be quite interested to try that just to see what it felt like, just not at expense of a new frame! But I expect it would be a non-event.

    • Superpilot

      Twitchiness from shorter stem comes from having a shorter arc to achieve the same steering angle compared to a longer stem. The ends of the handle bar are moved less distance to achieve the same steering input. Hence, the same steering movement on a shorter stem provides more steering movement, making the bike more responsive to the rider input. You are correct, twitchiness can come from wheelbase and trail, i.e. a track bike (shorter/steeper) versus a touring bike (longer/shallower). But then you can make the bike more reactive by altering the stem length. I recently switched from 110 to 90mm (sore back), and I concur it is more twitchy. E.g. riding one handed when feeding or some other admin on the bike is way more twitchy (rider input/holding the bars reacts more to road bumps, and also quicker reaction to rider input), but the bike rides the same when hands-off-bars doing up a jacket (independent of rider input, bike geometry and balance alone influence this).

      • velocite

        I understand all of that, but to me it’s not helpful to conflate the inherent twitchiness of a frame with the effect of stem length. If I read a bike review and it suggested that the bike was twitchy and it turned out to be because of a short stem I’d say that was misleading. You can’t make a car understeer by increasing the steering ratio, even if you do alter one aspect of the driving experience. And of course bike rider experience is a function also of handlebar design, specifically the width, reach and the length of the drops – and where you’re holding them: on the tops, the hoods or the drops.

        I would have thought that after a bit of time on your 90mm stem you’d have adjusted to it, and forgotten what the longer stem was like. No?

        • Superpilot

          You are right, the car wouldn’t suddenly under or oversteer, these are differences in front to rear traction, and inherent in the design. As you say, changing the steering ratio does make it feel more or less reactive. So it is the driver input and their feeling that is altered.

          Like any change in the bike, you get used to the feeling and alter your input to suit. But you do remember how the old setup felt. I do feel it even more necessary to descend in the drops, but they are also more comfortable. And that is from someone who used to use the drops a lot and comfortably previous the change anyway.

          But that is not for mostriders, just can afford a new frame to fit a longer stem :)

        • Bjørn Haug

          Velocite – the title of the article is “How does stem length affect a bike’s steering and handling?”. It points out that on two otherwise identical bikes, the one with the shorter stem will be less stable, more responsive to steering and can appear more twitchy, and it explains why. These are highly relevant facts to cover in an article about stems.

          Sure, there are other properties of a bike that can impact stability and twitchiness to a greater degree that stem length can, as I am sure everyone will understand. If some don’t – the article even spells it out: “When viewed in the context of the entire bike, the influence of stem length is relatively minor.” The article is not dedicated to explaining all aspects of a bike causing instability or twitchiness!

          As for your last comment (rider quickly getting used to different stem length), even this is already covered in the article “Most riders will quickly adapt to any stem length as long as it serves the reach they need.” Bottom line – not sure what your argument is. The article is great and informative on the topic it sets out to cover.

    • peter

      try a frame with a shorter top tube and put a 130mm stem on, make sure your saddle to bars is the same , the handling at speed is much better.

  • BrickDescender

    Froome is still staring at this article…

    • Ollie

      Clever ????

  • Stem envy? Check out Andrey Kashechkin’s 200mm stem

      • jules

        what is he compensating for?

        • Arfy

          With a stem that long it’s not your knees at risk of hitting the top of the steering tube …

          • jules

            oh, I just realised what he’s compensating for – a World Tour licence :-)

      • SeanMcCuen

        whoa, wtf?

      • Nick

        He’s smashing 79 watts without even sitting on the bike

        • Henry

          LOL thats the HR box…
          “Cyclists heart beats while bike is static – shock”

        • PlodrPete

          Motor output?

    • Pete

      Yes, he has a long one but it doesn’t look terribly thick. I wonder how stiff it is

      • SeanMcCuen

        stiff enough.

      • LeeRoy

        stop it

  • echidna_sg

    just dont go changing your bars from 3t ergonova pro to ergonova ltd without checking the reach… I gained about 15mm of extra “stem” thanks to this!

    • winkybiker

      This is an excellent point. With a variety of bar geometries and dimensions available, this needs to be considered. Switching between a short/shallow bar and a traditional bar is quite significant.

    • Richard Smith

      What!? I have both of these bars and the reach is identical on both of them. The 3T website confirms this. Please post pics.

      • winkybiker

        I was thinking the same thing. I have the “Rotundo” and they quite different to the “Ergonova”, though.

      • Steffo

        I have inspected and measured the counterfeit 3T bars. They look similar to an ergonova until you run a tape measure on them. I’m guessing this is the case here.

  • Simon N

    Something not mentioned here is mechanical advantage. A shorter stem can result in more immediate steering, but requires proportionately more effort, vs a longer stem that needs to be pushed more, but requires less effort. Or at least, that’s what I think is happening. If true, it may explain why a long stem feels solid on a descent (when your position is locked in), but a tiny bit wiggly on a climb, when you’re moving about on the bike.
    I don’t know. I’m not a stem scientist.

    • Hamish Moffatt

      Isn’t that the what the “Steering Arc” section is getting at?!

    • jules

      the physics of steering are complex and in fact – disputed. it involves precession and is not as simple as the stem acting as a lever. you actually push forward on the bars to steer the bike, so in that sense, lengthening the stem doesn’t increase your leverage (which would be measured from hand position to longitudinal axis of bike) anyway.

      • Arfy

        I thought that as you counter-steer you push the “inside handle” of the bars forward so that the front wheel turns slightly outwards, resulting in your balance tipping the bike into the corner and the mechanics of the bike then turning the front wheel to compensate. Is this disputed, I’m interested to know?

        • jules

          no it’s based on precession. leaning the bike doesn’t make you turn, rather it’s just good old rotating the front wheel so it tracks around the curve you want it to. the question is how to make a spinning wheel rotate in that way (around the vertical, or near vertical axis). if the wheel was stationary, pushing your RH against the bar would rotate the wheel to the left. but when spinning, it rotates to the right – due to complex physics. conventionally this is explained by precession but apparently that’s now disputed, or at least I read.

          • velocite

            My understanding is the same as Arfy’s. Everyone initiates a turn by counter-steering, whether they know about it or not. You turn the bars to the right to cause the bike to lean to the left, after which you can steer into the turn. I believe precession actually assists this process, because the gyroscopic effect of the spinning front wheel means that turning it to the left makes it want to lean to the right, which is what you want. I am open to enlightenment on this issue, however!

          • Alan

            Yes, there is such a thing as precession. No, it is not very complicated. See http://scienceblogs.com/principles/2015/03/24/how-does-angular-momentum-emerge/

            However, precession has very little to do with the steering and dynamic stability of a bicycle. See http://rspa.royalsocietypublishing.org/content/463/2084/1955
            Unfortunately, this requires a good understanding of matrix algebra, anholonomic constraints, advanced calculus and asymptotic stability.

            I wrote a review article on this subject, many years ago, but got little further than
            Sharp R.S 1985 The lateral dynamics of motorcycles and bicycles. Vehicle Syst. Dyn. 14, 265–283

            Too long, didn’t read version: despite its familiarity and apparent simplicity, there are only a few dozen people in the world who understand bicycle steering (I’m not one of them) and they all agree that precession is not particularly important.

            • Mark_Kelly

              There’s also a follow up paper (http://www.sciencemag.org/content/332/6027/339.short ) where these authors show that a bicycle constructed with counter-rotating wheels (to eliminate precession) and negative trail is still stable, putting many old myths to rest.

              • Arfy

                I find all this quite interesting, even if I don’t follow exactly where all of the math derives from. Are there similar models for a bicycle with a rider, enabling us to explore the differences in contact points to bicycle handling? From the article it seems that bicycle dimensions are based more on subjective than objective science.

  • maxy

    Funny that in MTB stems are shrinking by the year. 150mm t-bone back in the day, now the cool kids run sub 60mm, and there’s a real movement to get frames longer and stems shorter.

    • Frank

      I think this goes hand-in-hand (pardon the pun) with the movement for wider bars in XC and Enduro. Once you have a 710mm (or wider!) bar you need to shorten the stem reach to accommodate the effect of a larger distance between your hands.

      • winkybiker

        There’s a MTB that is stored in the bike locker at work. The bars are so wide, each of the racks on either side are unable to be used. Just ridiculous.

    • sps12321

      also goes along with the increased ease of steering at slower speeds.

      • Santoman

        plus the fact that, when negotiating a steep trail, there is no need for too long a stem to weight the front wheel. I went from a 90mm stem a few years ago to a 50mm one nowadays (and from 710mm to 780mm-wide handlebars) and the difference in control when things get steep and tecnical is amazing.

        • RC

          But then what happens when you climb? Does your front tend to wander more since there is less weight over the front wheel? I just went from a 125mm stem to a 40mm stem on my MTB, and my knees hit the bars while turning. I may have to try a 60mm or 80mm stem. But I don’t see what the big deal is with the short stem. I don’t really notice anything different. I originally wanted a shorter stem to make manualing easier so that I could bunny hop.

  • SeanMcCuen

    good article. dialing how you interact with a road bike takes a fair amount of thoughtful consideration, it is nuanced and a game of millimeters.

  • CC

    Matt – great article, though really…it’s all fashion -:) hipsters are rocking old school steel, with 60mm stems and uber long top tubes…

  • Hollis Duncan

    I’ve got a beater that I’m considering putting a 90mm stem on. I currently ride a 110mm stem but always on the bar top. If I go to a 90mm stem I think I will ride on the hoods more. In this case a shorter stem may actually put my position more forward. Whereas the opposite is true if we’re talking road bicycle where majority of the riding is done on the hoods.

    • jakub

      Riding on tops all the time indicates incorrect reach. Shorten your stem.

  • peter

    I always choose a frame that has a 53.5 top tube so i can use a 130mm stem, im 5’9. I once read that Mr Colnago designed his frames around a 130 stem being used.

  • brucegray

    A more pragmatic treatment of stem length would start with center of gravity relative to bottom bracket.

  • jakub

    I think that far more detrimental to correct weight distribution on bike is saddle setback, not stem length. Any serious bike fitter will try to achieve this by first setting setback correctly, rather than addressing stem length. Steve Hogg explains this on his blog in more detail. Correct stem length should mainly ensure proper reach to bars…

    • velocite

      Is it not pretty well universal to position the saddle such that your kneecap is vertically above the pedal spindle? If so you can’t use it to adjust weight distribution.

  • Cyco

    You also need to look at body proportions when selecting a TT/stem combo for a rider fitting.

    Forearms like Popeye and a long stem would give a huge front wheel weight percentage, but the longer stem is needed to give some weight on the front wheel for the rider with skinny arms, and a big gut, who can’t/won’t lean forwards.

  • Allez Rouleur

    I’d love to see some more photos of those classic steel bikes. A few of them look awesome.

    Also, not sure about the lead photo of the Deda 35mm bars/stem – never seen someone not wrap a round bar on the tops.

    Yep, I have a bike stored at a pals and when I ride my modern LOOK out there (compact geo) with a 110mm stem, then jump on the bike (traditional geo) the 80 mm stem makes the handling feel really weird for the first bit of the ride. That’s why I picked up a NOS Cinelli XA in 110.

  • jason hamlin

    a nice reference for people if they’re unsure about what they’re sold at a LBS. I just built a late eighties 49cm bianchi 7speed road bike into a flat bar town bike for the wife. The existing, extremely short stem puts rider weight behind the front wheel contact patch, which is twitchy at slow speed, almost impossible to ride no handed, add a heavy messenger bag from the grocery store, the problem is worse. Touch the “grabby” front brake, at slow speed and it’s downright dangerous. timely article which explaines why she now has bandages on her knees, palms and a destroyed brooks leather o-ring grip!

  • Solar Sailer

    I love my S-Works Venge with 100mm Alu stem + Carbon bars but the front of the bike can be very ‘twitchy’. The whole bike is insanely light which might be part of the issue. I contrast it with my training/commuter bike which is about a kg heavier and the steering is much smoother.

    If I understand the article correctly would adding Alu Bars to my Venge (effectively adding more weight to the front) help calm the steering down?

  • Rohan

    Matt clearly isn’t very good a physics as that section on weight distribution is incorrect. The load must pass through the hubs. The percentage of weight that passes through the front and rear hub is dependent on the centre of gravity of the rider and bike. Doing some quick napkin maths. Moving the riders hands forwards by 50mm may move the riders COG forward by say 1/3rd of that (assuming the rider doesn’t slide forward on the seat) which would be approximately 17mm and it won’t move the bike’s COG so you may be looking at a total COG change of 15mm. So with a bicycle with a 1000mm wheelbase you are looking at 1.5% change in the load on the front hub. I can’t see that making much of a change to how the bike steers.

  • justanotheropinion

    Cycling has now been reduced to stem length. Plenty for the mammals to talk about now at the coffee shop, just be careful when clad in Lycra.

  • elevenvelo

    There are just too many variables to be able to simply pin it down – frame geometry, bars, saddle position (fore/aft), rider’s physical size etc. etc., and like a lot of other things about frame design, there is a certain amount of black magic that each frame builder has that rarely coincides with other frame builders.

    As mentioned below somewhere, the weight distribution factor is nominal, unless you are out of the saddle. Stem length will affect the way the steering responds unless the bar width is altered to match, as has been mentioned with mtb’s. From where I sit, what affects a bike handling most is the fixed combination of wheelbase and overall geometry – CS length, BB to front axle, rake and trail. As these are fixed, you might (for example) be able to quieten down a twitchy bike with a longer stem, but it’s still a twitchy bike and the addition of a longer stem will cause other issues. Same in reverse, a ‘slow frame’ can have the steering be sped up a touch with a shorter stem, but it’s still a slow frame.

    And of course this does not even take into account personal preferences in set up and bike responsiveness. EG. I prefer a fast handling frame over a slow one as I want the responsiveness when I do something on the bike. So for me, a ‘steeper’ frame with a 100mm stem is a good combo.

  • ronboi

    Shorter top tube(when keeping head angle the same), and the longer stem = shorter front wheelbase and easier drafting on the rider in front of you. 2cm,,,,or better 3cm can be beneficial.

  • Mario R

    I think cockpit length is more vital than stem length… There are several handlebar reach dimensions available, starting at 72mm to 90mm. although for arguments sake, buying a stem to adjust cockpit length is more cost effective , if you have the right handlebar shape that you would like to keep.

  • Spanophile

    Motorbikes have no stem length at all. The handlebars come from the top of the forks.The only logical difference stem length can have is over weight distribution. Narrow handlebars do make for twitchy motorbikes or bicycles but stem length does not affect fork movement as there is no leverage effect.

  • Phil Hig

    Interesting article, but it does not answer the question: I’m buying a new bike, I’m 5 feet 7 inches tall (170cm), inside leg 30 inches (76.5cm), shoulder width 15 inches (38.5cm), torso length 60cm (23inches), arm length (armpit to end of clenched fist) 66.5cm (26 inches), neck 5 inches (13.5cm). Type of riding = road, club rides or sportive. What length of stem should I buy ?
    Been riding the same Raleigh 531 tubing bike for 25 years. Frame size 21 inches.


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