RoadBikeReview.com's Forum Archives - Components


Archive Home >> Components(1 2 3 4 5 6 7 8 9 10 )


what length cranks are u using and inseam(9 posts)

what length cranks are u using and inseamssuperx10001
Dec 24, 2003 11:59 AM
trying to decide what length cranks i should use i have 33" inseam,i have been using 175mm which came on my bike,but just got fsa carbon team but dont know what length to use
thanks
re: what length cranks are u using and inseamMShaw
Dec 24, 2003 1:27 PM
I'd say if you're riding crits, stick with the short cranks. For riding centuries, cruising, fast but not racing rides, then 177.5s or 180s are probably a better bet.

Take this for what its worth from a guy with a 30" inseam riding 165s on his track bike, 170s on the road, and 172.5 on the mtn bike.

Mike
There's no formula for crank lengthKerry Irons
Dec 24, 2003 4:23 PM
You will find no high quality data to support any particular crank length as being better than any other. This is true whether or not you correct for leg length, femur length, etc. What little research has been done on crank length suggests that people adapt to different crank lengths and there is no optimum or formula related to body proportion. On the other hand, you will find lots of anecdotal or low quality data to support all kinds of conclusions, and more theories than you can shake a stick at. A rider's response to changes in crank length is 1) highly individual, 2) dependent on riding style and the event (TT, climbing, crits, track racing, etc.), and 3) most important, highly adaptive. This is why it is so hard to study the effect of crank length.

It is generally the case that longer cranks make it harder to spin, and high cadence is the best way to minimize knee problems. That said, an extra 5 mm in crank length may only take away 3-5 rpm of spin, so it is not a large effect. Spinning is more physiologically efficient, all else equal. It is also something you have to practice - you can't say "I can't spin" unless you have spent some serious time working on it, day after day over a season or two. The primary disadvantages to low cadence are 1) harder to accelerate quickly starting from a lower cadence, 2) you'll have less left late in a ride, 3) risk of knee problems, and 4) you have less "turndown ratio" in your gears. If your total range of cadence is 50-60 up a steep hill to 80 on the flats, you need to have a wider range of gears to get you everywhere you want to go. If you can comfortably spin up to 110, then you can go 35 in a 53/13. If 80 is your comfortable cadence, you need a 53/11 to just go 30.
There's no formula for crank lengthrussw19
Dec 24, 2003 6:21 PM
Exactly what Kerry said! There is no formula, and you may not even notice any difference. I have a 31 inch inseam, I have one bike with 170's, two with 175's, and one with 177.5's (the one I ride most) and I can not tell any difference between any of them.

Russ
There's no formula for crank lengthil sogno
Dec 24, 2003 9:50 PM
Just to throw an aching monkey wrench into the works, take a listen to my ferkokte story. My inseam is 30" and I have one bike with 170's, one bike with 172.5's and one bike with 175's. The only bike that never gives me knee or leg problems is the one with the 172.5's. The 170's don't give my knees enough range of motion. This eventually brings pain beneath the patella. It also causes the muscles around my knees to fatigue. The 175's, meantime, take my knees through a large enough motion to sometimes make them click. The 175's are also just plain difficult to spin. Luckily, they're on the MTB. As for the 1725's, they are like Baby Bear's Porridge: Just right. Oh poor me with the poor senstive knee(s)...
Ferkokte?Noam
Dec 27, 2003 2:32 AM
Wher did you get the term "ferkokte" from?.
isn't that yiddish for "messed up" or "wild and wacky?bicycle268
Dec 27, 2003 7:18 AM
I think Kerry's analysis is spot on. Now what about stem length? ;-)
It's Yiddish for Screwed Up nmil sogno
Dec 27, 2003 10:57 PM
re: what length cranks are u using and inseamSintesi
Dec 25, 2003 6:51 PM
I'm reading Chris Carmichael's new book "The Ultimate Ride" and interestingly enough he writes that crank length is a function of frame size.

< 0r = 54 cm - 167.5-170mm
55-57cm - 170-172.5mm
57-61cm - 172.5-175mm

> or = 62cm - 175mm

For TT set up add 2.5 to 5mm.

All measurements to be tempered by personal experience as to what works best. How's that as a cop out?

Essentially there is no rule but merely generalized guidelines.

My understanding that any leverage advantages that come from crank arm length can be rendered moot by the gearing you choose.

I have a 53cm frame and use 172.5s. I'm happy.