Crank Lengths - What Impact?

[MacB]

Hi, been looking at variois cranks and just wondering what ifference the length of the crank makes. I can only think of rotational circle size and ground clearance. Does it have a greater impact on fitting etc?

 

[montage]

I think the longer the crank - the greater the leverage? I may be mistaken there.....

 

[Dave5N]

Marginal. I like shorter cranks - longer off road, but I don't believe it makes much difference unless you take a very dedicated position, such as a top tester.

After all, how good is your bike fitted to you anyway?

 

[Dave5N]

I think the longer the crank - the greater the leverage? I may be mistaken there.....

My maths isn't what it was, but 2.5mm really doesn't give that much more torque.

 

[kyuss]

I've got all three of the most common sizes on my bikes. 170 on my fixed, 172.5 on the good bike and 175 on the cheap commuter. I really can't tell the difference. Get as close to ideal as possible then forget about it.

 

[Steve Austin]

This will be about 50 pages by the time its finished!!

Loads of theories, loads of reasons of differing theories. no real science.

The only thing i think that is at all relevant is how long are your legs.
Long legs-long cranks
short legs- can you guess what i think?

Shorter cranks are allegedly easier to spin
longer cranks allegedly give more leverage

but as i said there is no proved science on this, just lots of unsound theories.

 

[jimboalee]

Yes Steve Austin.

If you have long legs, get some long cranks. Then you have an advantage.

My Pug has 170 cranks and I have 33" legs. Tommy Simpson had 35" legs so he used 175 cranks.
I rode Tom's bike ( the works issue ) and they did feel different. It seemed ( psycology I expect ) to climb easier.

 

[piedwagtail91]

I don't think it makes that much difference. I had to ride our clubs 150 mile ride with one crank longer than the other,due to one cracking, and couldn't tell the difference and never suffered any ill affects. A clubmate had his best reacing season and it was only at the end of it when he stripped the bike to clean it that he realised he had been using different length cranks all season.

 

[Joe]

If you're on a hill steep enough to bring your cadence right down then longer cranks give more leverage, otherwise it's hard to tell!
Didn't Pantani (5ft 7) ride 180's?

 

[Tim Bennet.]

There's that bloke in the States who's a great advocate of matching crank length to leg length, but to be meaningful, he reckons the size option in cranksets would have to be from at least 150 to 200 not the 165/170/175 options that are around. He says those sorts of variations are just fashion.

 

[Steve Austin]

Backstedt rode 180 cranks, and he was ok. he is also a big lad with long legs so he needed them.

I ride 175 on all my bikes, mtb, cross, road. it works for me, i have got an inside leg of 35". If i was shorter i would ride shorter cranks. I do believe that you should use cranks in proportion to your leg length, but unless you are very short or very tall, then the standard sizes will be fine.

 

[alecstilleyedye]

i ride 175 on both road bikes, even though i'm only 5'7". useful particularly on the commute, as it means my feet are not as far off the ground if i have to stop.

as a spinner, rather than a grinder, the extra leverage is probably useful too.

 

[MacB]

my current is 175 and I'm shopping around for chainsets for my 2 new bike builds and was just curious as to whether I needed to stick to one size or not. I suspect 170-175 will be fine but I should avoid 165...thanks for the help folks....Al

 

[swee'pea99]

Think of the length of your leg. Then think about half a cm. (170 v 175 - the usual options). How much difference is it going to make? As someone else said, I've ridden hundreds of miles on non-matching cranks - made no odds whatsoever. This is strictly one for the 'train-spotters' among us...

 

[02GF74]

mountain bikes used to tend to have longer cranks than roud bikes ... .but from what I can see, road bikes are not having longer crnaks too (I refer to bikes for the same person as obvioulsy a bike for a very small pereson will be fitted by the manufacturer with shorter cranks than one for a very tall person).

I have 175 mm on mine excpet for one bike that I has shorter ones, it feels different but that feel may be becasue I know the cranks are shorter so it is in the mind.