Long cranks or short

[jpb]

Here it goes. I'm 6'3 and usually ride 175 length cranks on my chainset. I have just purchased an ultegra 6700 chainset but with a crank length of 170mm. I know that some people say short is better or vice versa. But...what's the difference. Will 170 be a big difference on hills/flats etc.

Thanks for looking and hope to hear back :-)

 

[Tintin]

I,m 6'2'' and use 175 crank arms on a 6700 ultegra for my Madone.

What other people say is irrelevent when it comes to setting your bike up as it needs to fit you not them. We are all different.

I guess you may get away with it assuming you wont feel the difference. 5mm is not much but it is if you've been used to 175 for a long time.

I say give it a try and if you dont get any discomfort or niggles then great !

 

[festival]

While using shorter than usual cranks will not hurt you , a bike well designed to fit someone 6'3'' properly will usually come with cranks of a longer length.

Assuming it is of some quality, eg having ultegra kit, is it possible they are not the original parts?

If so, see your retailer to rectify the problem. Of course, if its an Internet bargain, good luck.

 

[andrew_s]

Shorter cranks feel like a slightly higher gear in terms of required push for the same chainring/sprocket (something like 77" rather than 75" for 170/175 cranks).
See Sheldon gain ratio

Many people won't notice the difference in crank length. When the subject comes up there's often someone who confesses to having ridden around with odd cranks for quite a while before finding out.

If your cranks are 5mm shorter, don't forget to raise the saddle 5mm to match.

 

[GrasB]

You should be able to feel the difference if you have any kind of sensitivity to what you're muscles are doing (how people manage to ride on odd sized cranks without realising something is wrong I have no idea). You may need a few miles of adaption to get your muscles coordinated with the smaller pedalling circle assuming you have a fairly efficient pedalling motion. After that you'll probably find you're want to change down a gear a little earlier & you should notice a marginal increase in your average cadence (assuming you have a trip computer with cadence readout). When changing crank length to get the absolute best performance from your legs you'll need to change the saddle hight & fore/aft position so that you get proper leg extension at the correct point in the stroke, but that's only really applicable if you're racing &/or TTing at a high level. But all of that stuff is very minor, if you're talking about non-competative fastish solo & group riding you probably will only notice that gears seem slightly harder at times.

Performance wise, it's been found that people produce the same power over the same foot speed range across a wide range of crank lengths (135 to 220mm) once they've 'settled in' to the new crank length. You may also find you need to change the way you accelerate, the longer the cranks the better it is to change up a gear then accelerate to your preferred cadence band, with shorter cranks it tends to be better to accelerate from your preferred cadence band & then change up a gear.