Crank Arm Length

[dp_Dyl]

Okay, I have already made my first order of components for my touring bike thanks to all your help and I have two left place. I'm going to be getting the crankset this week. I've decided on my chainring size but not the length of the crank. I know there's little in it but what is the difference between lengths? For the record I'm 6ft tall riding 700c wheels.

[CREPELLO]

It's more to do with your leg length than your overall height. And so much more.
But it's also down to personal preference. You may be marked out as a 175mm crank cyclist, but in reality you may prefer 170mm.

[irc]

Almost everyone uses 170 or 175mm cranks. As you are at the high end of the heights range I'd say 175mm for you unless you have a huge body and tiny legs. For someone of average height it might be a trick call but I don't think you'll go wrong with 175s.

[rjb]

You can find various methods for determining crank length if you browse around the web - here's one for starter's
http://www.nettally.com/palmk/crderiva.html
Basically it says multiply your inside leg measurement in inches x 5.48 to give your crank length in mm

[ChrisButch]

Just a word of caution if you've been riding for many years with a particular crank length - but now discover that it's not the 'right' length for your size. Changing can put a big strain on your knees. What you now fit may theoretically be better for them, but the knee joint may be so set in its ways that any change will cause problems. It did for me!

[531colin]

Just a word of caution if you've been riding for many years with a particular crank length - but now discover that it's not the 'right' length for your size. Changing can put a big strain on your knees. What you now fit may theoretically be better for them, but the knee joint may be so set in its ways that any change will cause problems. It did for me!

I "accidentally" went from 170 which I'd ridden for years (and is probably "right" for 5'10") to 175mm.....not pleasant!

[meic]

I am very long in the leg but I have always ridden 170mm cranks until 18 months ago when I built a new bike with 175mm (which is what I "should" have had all along). I really do not like them, probably because my body and cycling has adapted to the shorter length.
You wouldnt believe that you would actually feel such a small difference.

I reckon that if you ride with a fast cadence you will tend to shorter cranks than "normal".
Also do you have enough toe clearance for longer cranks on the bike?

[andrewjoseph]

I've got 170 on my tourer, 175 on my mtb. i don't notice the difference when riding, but I do have different position and styles of riding on each.

Another factor to bear in mind is crank to floor clearance, this shouldn't be an issue but may cause issues with poor riding technique.

[Brucey]

I believe habituation is at least as strong an effect as physiology. A few people change after a long time and are happy because it is 'better', but many people, once they have a few tens of thousands of miles under their belts, find it difficult or uncomfortable to change crank length.

I also play golf, and see similar things happening. Most people become habituated to the clubs they start with, even if they dont suit them very well. Later changes to lie angle etc may have benefit, but changes to (say) swingweight or club length, -even ones which make the clubs inherently more suitable- are not always accommodated to.

cheers

[dp_Dyl]

Also do you have enough toe clearance for longer cranks on the bike?

I have size 13 feet

I've had a Trek 7.3fx with 175mm cranks for a few months now and I do sometimes get a little knee ache. I don't know what is on my old mountain bike which I used to ride. Maybe 170mm will do me well.

[zoxed]

Just a word of caution if you've been riding for many years with a particular crank length - but now discover that it's not the 'right' length for your size. Changing can put a big strain on your knees. What you now fit may theoretically be better for them, but the knee joint may be so set in its ways that any change will cause problems. It did for me!

Did you go to longer cranks ? I can imagine them causing transition problems due to increased knee bend, but I would have thought moving to shorter cranks would not be a problem ?
(FWIW I went from 170 to 140 sometime ago, and am very happy !)

[Brucey]

some wise words and a table of suggestions here;

http://www.sdeals.com/oscommerce/crank_length.php

cheers

[ChrisButch]

Did you go to longer cranks ?

Yes - 170 to 175. There was a time when it was very difficult to find anything except 170, so a lot of riders became habituated (like me) to a length which wasn't ideal.

[irc]

some wise words and a table of suggestions here;

http://www.sdeals.com/oscommerce/crank_length.php

cheers

That puts me at about 178mm with my 34" inside leg. So the 175s I use on all my bikes are clopse enough.

[niggle]

some wise words and a table of suggestions here;

http://www.sdeals.com/oscommerce/crank_length.php

cheers

That puts me at about 178mm with my 34" inside leg. So the 175s I use on all my bikes are clopse enough.

Puts me at 165mm All my bikes are 170mm of course....