Crank arm Length for 29er

[Sniffie]

Quite correct 5mm will make no difference in ground clearance of BB hight, especailly as your supposed to keep pedals level when you see an obstacle that might hit your cranks. Same applies for DH/AM bikes they have very low BB's and you dont hear them going on about clearance. The balance outweighs the occasional BB hit.

 

In my post I was referring to pedalstrikes and not bb hits. 5 mm makes a difference on a technical rocky climb believe me. Also on switchbacks going uphill can make the difference between an inside pedal strike or not.

[covie]

In my post I was referring to pedalstrikes and not bb hits. 5 mm makes a difference on a technical rocky climb believe me. Also on switchbacks going uphill can make the difference between an inside pedal strike or not.

 

Sniffie if i changed your cranks to standard length cranks without your knowledge you would never notice the difference in a million years as far as pedal hits go.

 

If you can judge a obstacle that will strike your pedals to a 5mm variance you have superhuman powers the rest of us are sadly lacking. If it made any kind of difference it would already have been marketed as such so people discard their stock cranks to go make some more retailers rich.

 

There is simply no way it makes any sort of difference, it will however make a difference depending if your physique dictates having shorter or longer cranks.

[Sniffie]

Sniffie if i changed your cranks to standard length cranks without your knowledge you would never notice the difference in a million years as far as pedal hits go.

 

If you can judge a obstacle that will strike your pedals to a 5mm variance you have superhuman powers the rest of us are sadly lacking. If it made any kind of difference it would already have been marketed as such so people discard their stock cranks to go make some more retailers rich.

 

There is simply no way it makes any sort of difference, it will however make a difference depending if your physique dictates having shorter or longer cranks.

I never said I would spot an obstacle that is 5 mm higher than the other. Your comment is pointless.

 

I can only add my own experience. I have two dualies both with 175 mm cranks. The first one's bb is roughly 10 mm higher above the ground than no 2. When ridden over the same rocky climb and on the same deeply trodden cattle path with the same amount of sag on the rear shock for both bikes, I do experience far less pedal strikes with no 1. If 10 mm more of clearance under the bottom of the pedal makes such a difference, then obviously even 5 mm will also help clear some obstacles. I know that according to cycling wisdom crank length is supposed to be determined by your femur length, and I do not have a problem with that. My point is this that even when shortening the crank form 175 mm to 165 mm, the resultant change in torque is less than 6%. Not a huge difference, and something one would through conditioning be able to cope with easily. According to crank calculators available on the web, my ideal length is 172 mm. 165 mm cranks would mean that I am 4% away from ideal. Certainly that is not to bad at all, and as I said before 10 mm really makes a HUGE difference to the number of pedal strikes I encounter. Thats my 2c's worth.

 

What bothers me a bit more is that by going 10 mm shorter on the cranks, I will have to raise the saddle 10 mm to have the same amount of knee flexion on the pedal stroke. Higher saddle = higher centre of gravity = less control?