jschen

Okay, given that perspective, my question to you in my previous post is answered. Within a reasonable cadence range, that seems to make sense to me. But clearly, if the cadence is sufficiently low, you will no longer be limited by aerobic capacity since you can only generate so much force. Yes, appropriate gearing would remove this issue, but you can only get your gearing so low, and it's also not practical to carry enough low gears to deal with, say, a 20% grade if you rarely encounter sustained grades above, say, 10%.

pecos

But Pantani was on EPO.

Occidio

Bah longer cranks giving a whole 2% isn't going to do much in my oppinion but hey, if they give you a placebo boost then all the more power to you. Traditionally the crank length has been 20 to 21% of your inseam. Going a bit longer wont affect anything unless you go so large that at the top of the stroke your knees are over compressing.

TimJ

This thread's a bit old, but I was mulling over the ol' crank length issue.

On my single-speed, 26" wheeled commuter bike I was running a 15t hyperglide cog and 42t front chainring. It was just about right, but slightly too high, so I got one of those shimano BMX cassette cogs, 16t. The change was really profound and I think it's got more to do with the long teeth on the new cog engaging the chain much more positively. But anyway, it's a bit too low now.

I was thinking I'd get a 15t BMX cog, but lately I've been bashing my pedals on the street, curbs, etc., a whole bunch and was thinking maybe I should go for a 170mm crank. Considering that, if I'm reading all this stuff correctly, the slightly shorter crankarms may make the 16t feel like the opld 15t, gearing-wise. Right?

15t was a bit too high, 16t a bit too low, shorter crankarms with 16t may feel like having a 15t? And spinning out with 170mm might mean actually a slightly slower speed than with the same gear ratio but 175mm arms? Right?

rhm

I just wanted to bump this thread back up because I've started a similar thread in the Folders forum:
https://www.bikeforums.net/folding-bikes/369756-crank-arm-length.html

Here the debate concerned the respective merits of 165 - 180 mm crank arms. I'm starting to think those are all in the "too long" range, so I'm wondering if anyone has tried significantly shorter cranks, i.e. less than 150 mm?

ChunkyB

Gross misuse of physics warning!!!!

Work has nothing to do with it. It's a question of torque. The farther the force is applied from the center of rotation, the less force is needed to create the same angular movement. It's kind of the same thing, but not really.

Giro

If you already spent the $'s for a PowerTap or equivalent, another $450 for this easily adjusted "Multi Length Adjustable Crankarm" would be the way to experiment:

LINK

AnthonyG

Yes I use 135mm long cranks but I have very short legs. For me its about getting a proportionaly correct crank length and its done wonders for my cycling. The trick when you go to shorter cranks is moving the saddle rearwards to maintain KOPS and not effectively move way in front of it.

Regards, Anthony

uberclkgtr

Yup. Arbitrary torque figures can be produced by anyone. Sustaining those torque figures over time requires specific power output by the rider. A longer or shorter crank will not change this. I suspect crank length should be matched to best suit the rider biomechanically based on his or her musculature and femur/lower leg lengths.

markwebb

I am a good climber. But I lack massive muscle and power. I get into trouble on really steep grades. I can out-climb most other riders when the grade is 8% or below - but above that my lack of sheer power and muscle shows. Would I benefit from a slightly longer crank - say 175???

rjtokyo

Here's my experience from going the opposite direction- with shorter crank arms:

I love to climb, and do 2-3 hillclimb races every season with grades between 6% to 15%, and distances of 20km-25km (12mi.-15mi.). I normally ride 170mm crank arms, but my leg measurement computes to fit about a 168mm crank arm. Someone convinced me I should try a shorter crank so I could spin a slightly higher cadence more smoothly, so I dropped down to a 165mm crank.

I log lots of training miles on the same hills, so I know the average speed and corresponding heartrate that I normally have on various climbs. With the 165mm crank, trying to maintain the same speed, I was noticably more tired, and had a higher heartrate than I normally did on my 170s. Also, trying to maintain the same heartrate, I was noticably slower on the 165's than the 170's. I agree with Terry M. that having a longer lever in your crank arms won't give you more power. That only comes from training and conditioning. But my experience tells me it gives you more torque, and therefore makes you less tired going up the same hill at the same speed.

Anybody want to buy a 165mm compact crank with very low miles? :-)

Next, I'm going to try some 175's

Cheers! - RJ