Crankarm Size Question

I looking at buying a new set of cranks. What is the deciding factor between 170mm and 175
mm cranks?

thanx

Biggibby

 

Sombody asked:

> I looking at buying a new set of cranks. What is the deciding factor between 170mm and 175
> mm cranks?

See: http://sheldonbrown.com/cranks.html

Sheldon "Cranky" Brown +--------------------------------------------------------+
| One man's theology is another man's belly laugh. | --Robert A. Heinlein |
+--------------------------------------------------------+ Harris Cyclery, West Newton,
Massachusetts Phone 617-244-9772 FAX 617-244-1041 http://harriscyclery.com Hard-to-find parts
shipped Worldwide http://captainbike.com http://sheldonbrown.com

 

Sheldon Brown <[email protected]> wrote in news:3E9C3788.3010303 @sheldonbrown.com:

> http://sheldonbrown.com/cranks.html

Great site! Thanx a lot!

Biggibby

 

Biggibby wrote:
> I looking at buying a new set of cranks. What is the deciding factor between 170mm and 175
> mm cranks?

Leg length, IMO & E. As a rough guide: 170 for average legs, 175 for long.

I find the theory that there's no downside to too-short cranks absurd. Imagine trying to pedal a
bike with ridiculously tiny cranks, say 60mm long. Oh yeah, that'll be very enjoyable, wouldn't it.

You need to turn your legs in a comfortably-sized circle so it makes sense to get cranks most
suitable for _you_. It's true that manufacturers don't provide enough choice to cope with everyone
but that's no reason to get the nearest to optimum length you can when next buying cranks.

Don't forget the difference of the circle diameter created by 175mm cranks as opposed to 170's is
10mm and not 5mm.

~PB

 

Sheldon has the meat of it, as usual.

May you have the wind at your back. And a really low gear for the hills! Chris

Chris'Z Corner "The Website for the Common Bicyclist": http://www.geocities.com/czcorner

 

>I find the theory that there's no downside to too-short cranks absurd. Imagine trying to pedal a
>bike with ridiculously tiny cranks, say 60mm long. Oh yeah, that'll be very enjoyable, wouldn't it.

Yeah, and 400 mm cranks would be quite a change as well! But the difference between 170s and 175s is
small, so either way, most people can accomodate easily.

>Don't forget the difference of the circle diameter created by 175mm cranks as opposed to 170's is
>10mm and not 5mm.

This means that out a 340mm circle, you have 10 mm increase in diameter, or about .4 inches in
13.4 inches.

Might need one to change the seat height a tad.

I ride 170s, 172.5s and 175s, I believe that I can notice a difference between the 170s and 175s but
it is only to notice it.

As long as the cranks are not too long, there seems to be little difference in performance.

jon