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Crankarm Lengths(5 posts)

Crankarm LengthsTad
Dec 4, 2001 5:51 AM
170, 172.5, 175.....how do I know what's best for me?
Experiment.MB1
Dec 4, 2001 8:03 AM
Generally the shorter you are compared to the norm the shorter your crank arms. It is also a matter of your pedaling style and the sort of riding you are doing.

I am 5'11", I've got 170s on my track bike, 172.5s on all my road bikes and 175s on my ATB. Compared to other riders I tend to spin an easier gear than most. Riders that like to use bigger gears and pedal slightly slower often find that slightly longer cranks work well for them.

You have to experiment with crank lengths to really figure what works for you under what riding conditions.

Good luck!
re: Crankarm Lengthscyclaholic
Dec 4, 2001 8:06 AM
Trying different things over time will let you know what's best for you.

I recently made a triple to double chainring conversion. I am 5'11" and fit to a 54cm frame, so that means my torso is relatively long to my legs. I am a spinner, too. So the book answer would be for me to go with a 170mm crankarm length, which is what I had. But just to try something new (my other bikes have 172.5), I decided to go with a 175. I like the 175mm better. I can definitely tell the difference; it feels as though I am spreading the work out better as I pedal. Without question, the 175 makes those tough hills just a little easier - or a least I think they do.
Lennard Zinn articleTig
Dec 4, 2001 10:45 AM
Here's an interesting article on crank arm length: http://www.velonews.com/tech/rev/crank.html

The test results were inconclusive, but worth looking at. I used to ride 172.5's for road but am experimenting with 170's the last few years. I'll put 172.5's on my next bike so I can compare with the shorter ones on the current bike. Maybe I can blame my recent poor climbing on the shorter cranks! I'm 5'7 on a 52 cm frame.
very personal...personne
Dec 4, 2001 5:27 PM
Am 180cm tall (750mm seat height), but very light and like to spin. I use 170mm for fixed wheel, 172.5mm for everything else. Can tolerate 175mm off-road, but since I use 172.5mm 95% of the time it's not worth the potential injury risk for basically no advantage.

On the other hand a friend of mine who is now primarily a MTB racer and rides a ~53cm road bike uses 175mm cranks for everything since it makes road training more specific to MTB...

The best solution is to try it for yourself... I found that 165mm cranks were useless for me (no leverage); 170 was okay on the road but 172.5 climbed and accelerated better with less knee trouble; 175 on the road drastically impaired my spin; 175 offroad helped a little while climbing but required a big time investment to feel comfortable; 177.5 offroad was great when climbing steeply *only*; and 180mm was hideously awkward at all times with no comfortable position attainable and extra knee stress.