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Old 09-07-12, 06:42 AM   #1
dbg
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Do sprinters use a longer crank or a shorter one?

Asking here in 50+ so I don't get flamed for asking a dumb question... I wonder if the added leverage is a good thing or a bad thing. Anybody know what the top sprinters prefer?
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Old 09-07-12, 09:21 AM   #2
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Back in the '80's when I first got into cycling I set my bikes up "by the book" of conventional wisdom at the time. That resulted in a 172.5 crank arm. My current bike has a 175 crank arm and I've noticed no difference regarding stress on my body.
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Old 09-07-12, 09:35 AM   #3
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Outside of Velodrome racing, ... on the Road, the sprinters do the same
hundred mile + day, as every one else, they just get themselves
with teamwork, of course, to the front,

and just go a little bit faster, than the next person, in the last few yards..

The cranks as part of bike fit ,I expect is same as anyone else their size..
leg length , etc..
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Old 09-07-12, 09:43 AM   #4
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You need to differentiate a bit between track sprinters and road sprinters, but, as a general rule, I believe sprinters tend towards shorter cranks, because:

A. You get higher rpm's for the same circumferential pedal velocity.
B. They are "Quadzillas", with enough torque to offset any reduction in leverage.
C. They tend to ride in very aero positions (especially on the track) and the shorter cranks allow a lower position without having your legs hit your body.

A top sprinter can be turning over 200 rpm, and they don't want anything to get in the way of their ability to do that. On a team Sky rest day at the TdF, they had a cadence competition. Cav won it by turning 220rpm.
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Old 09-07-12, 10:00 AM   #5
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I doubt 5mm matters that much..
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Old 09-07-12, 10:03 AM   #6
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Sheldon Brown on crank length: http://sheldonbrown.com/cranks.html
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Old 09-07-12, 10:18 AM   #7
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Originally Posted by bruce19 View Post
Sheldon Brown on crank length: http://sheldonbrown.com/cranks.html
When you say "sprinters", that puts you into racing territory, which was not Sheldon's primary interest, but I believe he was right to point out that shorter cranks are easier to spin, and to discount the overall effect of the difference. It's certainly a marginal thing, but the Great Britain team just pointed out to the world how important marginal gains can be. If you are racing, you want every advantage you can get. Racers I know who have experimented with different lengths haven't noticed big differences in power/rideability - unless it affects space between their legs and torso.

One other factor, not specifically related to sprinters, is that a long crank length also puts you at a disadvantage cornering. I use 175 cranks, and I will scrape the pavement with my pedal in a turn before my competitors with shorter canks do. That's a disadvantage, particularly in criteriums.
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Old 09-07-12, 11:45 AM   #8
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Most track sprints depend on leg speed in a medium gear (e.g., 88 to 94 inches), while most road sprints are conducted in the biggest gear you've got, so there's way more torque involved. As a result, for example, I would use 165mm cranks on the track (I was most successful in points races, which require the ability to recover fast from sprints happening every two kilometers, so you want to be spinning in order to flush the lactic acid from those efforts), and I would use 175mm cranks on the road (because I was such a lousy climber, I needed the extra leverage on the climbs, but it also came in handy for the flat sprints in 53x14, my best sprinting gear on a flat road - note that it's slightly lower to give me a better jump and to take advantage of more leg speed from being a trackie!).

You can see how much torque is involved when you look at the head-on camera angles in the big road sprints, especially at the Tour. Cav's bike is rocking way over to the side; he's just reefing on those bars! However, I find it quite notable that Peter Sagan has a much "cleaner" sprinting style, with the bike more upright. Mike Walden always told us to try to keep the bike upright as possible, as hanging it way over scrubs speed because you're rolling off the tire's sidewalls. I kinda think Cav could actually sprint faster if he kept his bike more upright, but then, you've gotta do what works for you.

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Old 09-07-12, 12:34 PM   #9
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Grand tour racers have the capability to change equipment every day and change bicycles during a stage. I know Wiggins did this and maybe Cav does as well. So Cav could start a race with a particular gearing and crank setup and change bicycles with 10k to go configured for his sprint. Once one gets a "good" bike fit using conventional fitting practice, it takes someone who really knows himself and has a specific event / race in mind to tweak things further.

I wanted to focus on pursuit at the track so I set up my pursuit bike with the same crank length as my road and TT bikes. Some pursuiters use longer cranks with the idea that they can pursuit faster in a bigger gear for the same leg speed. And as AZT said, the trend is to shorter cranks to get better aerodynamics because one can go lower and maintain separation between the thigh and chest.

I started doing the 500 meters which requires an explosive start and great finish. My 172.5 cranks are great for the start but limit my leg speed. So I could trade off shorter cranks for theoretically a slightly slower less explosive first pedal stroke but greater top end finish for the same gear. Testing and practice is the only way to test different configurations to determine which will yield a faster time. The same is true in gearing. I can use a 92 or a 94. I will start faster in a 92 but top out sooner than in the 94.

Match sprinters want maximum jump, acceleration and leg speed so typically they will favor 165 mm cranks and they typically, do not start from a standing start or it is not relevant. A smaller gear will require greater leg speed for a given speed but accelerate faster. Victoria Pendleton and Anna Meares, who were silver and gold medalists, respectively, are examples of spin versus force. Pendleton has some of the best leg speed I have seen and great acceleration. Meares uses a bigger gear and spins slower with more force. Both women have beat each other in events.

Since one can select gears on the road, winning a sprint comes down to having a great lead out, jump, aero position, a little luck and strong finish. Crank length optimization is a variable worth exploring and like my 500 meters requires testing to see which configuration works for each racer.
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Old 09-09-12, 09:43 PM   #10
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Quote:
Originally Posted by lhbernhardt View Post
Most track sprints depend on leg speed in a medium gear (e.g., 88 to 94 inches), while most road sprints are conducted in the biggest gear you've got, so there's way more torque involved.
Cav has said that most of his sprinting is not in his largest gear, although with his leadout train I believe he's using something a little bigger than the rest of us could push effectively.

As for crank length, short guys like Cav use 170s and big guys like Tom Boonen (who doesn't win too many sprints these days) use 175s.
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