Damon Rinard, Cervelo Engineer says:Hi John, Thanks for your comment. I like your article on crank length - very balanced in my opinion. It's a good reminder that "shorter is better" isn't the message - the message is "choose the crank length that works." Thanks for the link, I'll recommend it to others who are curious about changing crank length. Cheers, -Damon Rinard, Cervelo Engineer

John Verheul says:Hi Damon, I've been talking about stuff like this on the internet for some time (as have you of course), here's just one example: http://jbvcoaching.com/Cranklength.asp I wanted to say though, I think this is the best writeup I've ever seen on the various factors that got into choosing crank length for different athletes, and different applications. Not surprising at all, you know I've always been a fan of your work. Keep it up!

Damon Rinard, Cervelo Engineer says:Hi Edwin, Nope. Most of the structural benefit (stiffer, lighter) of BBright comes from the frame itself. The GXP is an excelent stiff crank system and will work well in your R3 Team. Cheers, -Damon Rinard, Cervelo Engineer.

Gibson says:Damon, Question not involving crank length directly but the cranks themselves. I have an R3 Team and I'm currently using a Rotor 3D+ crankset, but I'm going to be switching back to my SRAM Red GXP cranks. Is there going to be a significant lose in stiffness when going from a full on BBRight crankset to the GXP which requires an adaptor to go from 24mm to 30mm. Thanks Damon Edwin

Damon Rinard, Cervelo Engineer says:Hi Joe, to my knowledge 165mm is the shortest BBright crank. But I don't know everything. Anyone can help Joe with options for a shorter crank for BBright? Cheers, Damon

Joe says:Hello Damon, As a practical matter, are there cranksets out there under 165mm that will fit the new Cervelo P5, or BB adaptors that make it possible? I use 150mm cranks on my P3SL, but they require a square taper BB. Thanks, Joe

Damon Rinard, Cervelo Engineer says:Hi Veloflyte, Thanks for mentioning your experience with different crank lengths. Many of your comments mirror the feedback we get from our athletes, especially your comment about the crank length "making" you pedal faster or slower. I'd rather say the cadence is "automatic" but that's just semantics I suppose. Also, you may recall Bernard Hinault used to recommend *not* changing saddle height for different length cranks as well. It's an idea that's currently being considered for further detailed investigation. Thanks again for your comments. Cheers, -Damon Rinard, Cervelo Engineer

Veloflyte says:In response to what Ton Anhalt said about changing the saddle position for different crank lengths... Many years ago while I was working at the Wheelsmith Inc. in Palo Alto, CA, we had Miguel Indurain's Tour de France time trial bike at the store on display for a while. Now of course the bike had Miguels signature 180mm cranks on it, but there was one piece of information I got through the grapevine from Miguel's team mechanic... When switching form 175 to 180 cranks from his road to TT bike, Miguel didn't change his seat height at all.!! This was an interesting piece of information so I decided to pursue the idea further. I am now a strong believer in this type of fitting. I use three different crank lengths for my amateur racing here in California. 180 for the really hilly events, 177.5 for the moderately hilly, and 175 for any criteriums I might do. It really is an ideal situation in my opinion. My saddle is set at the highest point possible for the 180mm cranks, then I just leave it there and alter crank lengths accordingly. It leads me to consider the possibility that people should measure their seat height not from the bottom pedal, but from the bottom bracket center.

Veloflyte says:Look....after two+ decades of racing, training, and trying every crank length from 150mm to 190mm, I can give you the basics of this whole crank length equation... If you use long cranks, you pedal slower and have more immediate torque. If you use short cranks, you have to pedal faster to make up for the loss of torque. Using short cranks is good for short, fast events (I mean really short..like less than 1 hour). Using long cranks is good for longer events, like a long time trial. But..no matter what crank length you use, in order to go faster, you have to pedal faster. So..given the choice between a short crank that you MUST turn quickly to develop power, or a long crank that you can Learn to pedal faster to develop power, but have the ability to pedal slowly, especially if you're climbing, I always choose the long cranks. Short cranks are good for repeated, quick accelerations. Long cranks are good for steady state power development...like climbing or Time Trialing.

Damon Rinard, Cervelo Engineer says:Hi Tom, I understand. Naturally we adjusted the bars in the wind tunnel, but not in between the pairs of runs presented below. It would be interesting to follow the "Anhalt Protocol" and see the results! Cheers -Damon

Damon Rinard, Cervelo Engineer says:Hi maurice, I think we agree, except perhaps for this part: "...given the same downward force and the same cadence." In Martin's study, the subjects chose *not* to keep the same cadence. They self-selected a different cadence that balanced the change in crank length. The muscle-fibe-shortening theory explains this well. Cheers, -Damon

Tom Anhalt says:Hi Damon, I'm sorry if I wasn't clear, but I was wondering about other bar and saddle adjustments in the wind tunnel results...I'm familiar with how the Martin study was performed :-) If one moves to shorter cranks, in order to keep the relationships between the "touchpoints" (i.e. the saddle, the bars, and the pedal IN THE POWER STROKE) consistent, then IMO it's important to move the saddle forward the distance of the length change along with moving the bars up and forward as well commensurately.

maurice says:Hi Damon, I am not presenting an argument either way I feel that crank arm length is individual. Having said that as most of the effective force component that drives the bike forward happens on the downstroke longer cranks given the same downward force and the same cadence will generate more power, period. This is a function of torque, which is the length of the lever times the applied force. We get power when we multiply this by rotational frequency. There is no getting around this equation. The issue presents itself when we look at the individual athlete and if on the up stroke they are compromising power or wasting extra energy trying to turn a bigger crank (or risking injury). When changes are made to crank arm length neuro muscular adaptation takes between 7-10 days, this is always the last system to super compensate. Having said that we are doing a lot of testing on athletes at different crank arm lengths and there are some arguments in favor of shortening or lengthening the crank depending on the individual. we have seen some long term mid range power increases at longer crank arm lengths (we power test Ironman athletes at about .85 exchange ratio or about 75% of VO2 max) Having said that the biggest single issue we have with athletes is imbalances left vs right. So we are more focused on this as we view fixing issues left vs right leg as "free speed"

Damon Rinard, Cervelo Engineer says:Hi maurice, There is no free power. In your scenario, the "extra" power is provided by additional work the rider on long cranks has done: the foot has gone farther (around the pedal's path) with the same force. In practice, the RPM decreases. (See my reply to Trevor below.) So the "extra" power doesn't arrive. Cheers, -Damon

Damon Rinard, Cervelo Engineer says:Hi Trevor, What would you say if I told you a rider's natural cadence changes instantaneously with crank length? Individuals have an optimum muscle shortening velocity. Because of the geomtry of the various leg joints, a constant muscle fiber shortening velocity gives a roughly constant foot tangential velocity. So for the same "optimum" muscle fiber shortening velocity, the self-selected cadence naturally changes.

Damon Rinard, Cervelo Engineer says:Hi manuel, Short sprints aren't TTing for sure. But Dr. Andy Coggan, respected physiologist and competitive cyclist, can't think of any physioloical mechanism that would change the result in sub-maximal eforts. If you feel better on longer cranks it may be true in your case. But don't base conclusions on Fabian - he might not know either! Cheers, -Damon

Damon Rinard, Cervelo Engineer says:Hi James, You askgreat qestions, the answers to which I do not know! Sprinting is a avorie of Dr. Martin's. Maybe I can ask him to consider your theory. Cheers, Damon

Damon Rinard, Cervelo Engineer says:Hi ron, Correct: lowering the bars to keep hip angle constant is often an element in lowering aero drag wth shorter cranks. Yes, maintaining a contant leg extension. Cheers, Damon

Dam Rinard, Cevelo Egineer says:Hi Tom, Dr. Martin only changed sadde height, no changes to bar height, saddle position on the seat post, etc. You may be right that bars *could* be adjusted, but considering how insensitive power is to changes like crank length, I wonder if any significantly different results would be found. Jim has suggested *not* changing sadde height a well, on the thory that some power is thought to be aided by pre-tensioning the muscle fibers. -Damon

maurice says:Watts are a function of rotational frequency (cadence) and torque. Torque is a function of applied force times the length of the lever (in this case the crank) Gearing in no way shape or form affects leverage, it affects the force we apply against a resistance (in the case of a bike the gears we choose) There is no leverage "myth" plain and simple if you increase the size of the crank and were to apply the same force at the same cadence your wattage would go up with longer cranks. If you were to attach a machine that applied equal force it would produce about 12% more power at a 180mm crank than at a 160mm crank. So according to accepted and tested principles longer cranks would create more power. Thankfully we are not a bunch of machines racing in labs, so the main issue is the strength and frequency of firing patterns and how they are affected by changes in crank arm length, there is also the strength of the athletes joint structure and how that will be compromised by going longer/shorter. So which is better long or short? Depends, on the event (long cranks might be bad for crits!) and the athlete, if you are a "spinner" it is unlikely that you will feel better on longer cranks, If you are a "masher" who turns over at 50-60 rpm then a bit longer might feel better!

Al says:Certainly shorter cranks are better for smaller riders. Additionally to the aero, comfort & clearance benefits, it becomes easier to unload the saddle for more balanced cornering. It is always necessary to gear down with smaller cranks however. The same gear will "stall" more readily on steep hills, and your preferred foot speeds for given momentum levels & gradients will remain the same.

Trevor says:I think crank length has more to do with a riders cadence preference. Riders with powerful legs and lower cadence would get more out of a longer crank. Riders who get more of thier speed from higher cadence with less leg power will lean to a shorter crank. I think this is the reason TT and Tri riders lean twards a shorter crank as they get more of thier speed from heart and lungs (higher cadence) verses raw leg power (low cadence). It was once explained to me you can get your speed from legs or heart/lungs. High cadence is heart/lungs and lower is using more legs. The key for a rider is to know how much you can get from each over the race. Stage racers will use heart/lungs more as the recovery time for legs can be days while heart/lungs can recover much faster.

PETER-D. MUNOZ says: I will be getting the Cervelo s5 next year. I found your article inciteful and a conformation, if nothing more, 170 better than 172.5, if only for better ground clearance. Technically 2.5 mm will not hurt me, if I experiment, but 2.5 mm will make a big difference in not hitting the ground with my pedal-on very tight turns in a race. Heh, that is part of the adventure. Why not go for a little veriaty. By the way, I am 5'7" so it would be a minor change, but have the potential for greater effects. Gentleman, let us not ever be stuck on any one oppinion, but be open to other statistical possibilities-especially when it could improve seconds or even minutes-hey with great imaginations, great things can be possible. CERVELO IS THE BEST! THANK YOU.

manuel says:i still think that longer is better. maybe the problem is that dr. martin uses short four seconds sprints in his test ,and that effort has nothing to do with a TT or the bike leg of a triathlon. b I think that short crankarms are better for sprinters, medium for roadies and the longer ones for time trailers. I am not sure ,but I believe that fabian Cancellara uses 175 mm crankarms in his road bike and 177,5 in his TT-bike.

Tom Anhalt says:Damon, was only the saddle height changed along with the crank length changes? IMO, for an "apples to apples" comparison, the bar height should be changed accordingly, along with the saddle and bar fore/aft position to maintain the same leg-pedal relationship through the "power stroke".

James Parker says:A GREAT article guys. Very informative and reassuring for many riders out there including myself... I wonder if any thought has been given to sprint efforts say in a road race. Shorter cranks and in turn a higher cadence at close to max effort repeated would yield lower fatigue would it not? Or worst case promote a more efficient recovery?

Tim says:Great article! I'm sightly over 5'9 riding a 51 S2 with a 172.5mm crank and I've just ordered a 170mm crank as I've felt that my knees are too tight to my chest when I'm in the drops or with the aerobar popped on. I've heard from fellow riders and triathletes who have switched down crank sizes that their cadence has gone up and has made the transition from bike to run easier. Another brightside is that I'll have a little less two overlap which can be frustrating at times. Thanks for ther great info!

ron says:is it possible one potential reason for inclusive aero data being that a shorter crank length would allow a lower position while maintaining a similar upper leg to torso angle. So if this upper leg to torso angle was controlled for maybe the results would correlate better? also the aero data is, I assume, maintaining a constant leg extension. One point for power data is that a change of crank length vs the radius of pedal travel is really only a difference of less than about 0.5% and would likely be swamped by other variability in the system and would fall into the measurement uncertainty and not show any statistical difference assuming for statistical significance they use at least a probability difference of 0.5 or put another way outside the 95% confidence interval for the compared data sets. In the end as is stated in Dr. Arnie Baker's book on bike fitting that one should not change crank length for TT or Tri. In short I tend to agree with Damon, it is not going to really make much of a change one way or the other. What you believe (the placebo effect) is probably more influential than the biophysics of the change. As well with longer cranks there is the issue of ground clearance when turning and would probably be bad in criteriums or tight courses where it might be possible depending on the frame size for the the pedal to hit the ground.

Don says:Very informative, thank you. It is an issue that I have have thought about. When opportunity arises, I will likely choose the 165 mm crank length and will feel more confident in my choice.