Crank arm length formula?

Stewie Griffin

Having seen all of the threads about seat post height and various percentages of ones inside leg measurement, is there a formula for crank arm lengths? I dont think whats on the bike now is the wrong size just that perhaps its not the most efficient length and if Im going to upgrade that (and therefore probably the whole drive train 8) ) I want it to be correct, for want of a better word.

Doobz

dont know of a specific formula but I do believe if you have long femurs you go for longer crank length.

sub55

http://www.machinehead-software.co.uk/bike/cranks/crank_calc.html

Cajun

http://www.cptips.com/crnklth.htm

Stewie Griffin

Cheers fellahs, I seem to "need" 175mm. Then again, another bit later on said 172.5mm. Aaaarrgh :? I knew it wouldnt be black and white. Whats on the bike now feels perfectly fine and I guess I should go for the same length. However, whether or not I get Ultegra or Rival is the really big decision

redddraggon

Stewie Griffin wrote:

However, whether or not I get Ultegra or Rival is the really big decision

Of course you'd only be making the right decision if you went for Centaur.

Stewie Griffin

Stewie Griffin wrote:
However, whether or not I get Ultegra or Rival is the really big decision


Of course you'd only be making the right decision if you went for Centaur.

Isnt there a Euro Cyclist rule that says that thou shall not have Shimano and Campagnolo on the same bike? Or was it just thou shall not have Shimano?

I feel like a kid all over again, shall I have cola cubes, pineapple cubes or rhubarb and custard? I have an Allez now but intend to build something a bit more top end once I believe I deserve it. So, should I get a Rival, Ultegra or even a Centaur crankset now and leave it on the Allez which will become my winter bike OR shall I go overboard now with the intention of putting that on the new bike later? Will I then want to put a not new crankset on my new shiny Frame? No of course not. So, Ultegra, Rival or, perhaps, maybe Centaur :roll:

System_1

The problem with a lot of these online crank length calculators (and bike size calculators) is the writers of the programs all seem to have different views on what is ideal. I did a few of these a while back and they all gave vastly different readings ranging from 168 to 195. :shock:

Since there only seems to be 3 easily available sizes (170, 172.5 and 175) it should be fairly simple to judge. If you're short get 170, if you're tall get 175, everyone else get 172.5. In the end I doubt 5mm is going to make any significant difference.

Felix-da-house-mouse

i've had a ee look at this and it gets a iffy, where do you measure the start of thigh from and to? lower leg from and to etc etc my inside leg 31" to the ground and approx 29 to 29.5 to my ankle bone so what does that make my crank arms ideal length.i reckon somewhere between 155 and 160 but i'm unsure

Stewie Griffin

I have taken one measurement from my groin to the floor. This reads 88cm, Im 184cm tall. After all of this I have decided to go with the same length as spesh put on the bike originally. Well, as long as its a 172.5 or 175 otherwise I will be quite confused. I said in the OP its not uncomfortable, I just wanted to make "sure".

Thanks again everyone.

pneumatic

Read this:

http://sheldonbrown.com/cranks.html

and be reassured.