Crank length

[Twilkes]

At the weekend I raised my seat by half an inch and today my balls hurt, but that's by the by.

It did get me thinking about the length of my cranks though. My saddle is usually high enough that anyone who has to try to ride my bike comments on it, sometimes using swear words. But my thoughts were that longer cranks would mean my straight legged foot would be closer to the ground, meaning a lower saddle height reducing air resistance, and longer cranks would mean my knees were getting higher meaning a greater range of my leg muscles were being used.

But I also read that any change in crank length could be compensated by a change in gearing, so it's really not worth bothering. Is it really not worth bothering?

My current cranks seem to be 175mm from the axis of the pedal to the axis of the crank. I'm 6ft5 with a 34inch inside leg.

 

[smokeysmoo]

FWIW I'm 6'5" too.

My best bike has 175 cranks, my fixed gear runs 165mm cranks on the road, and 170mm on the track.

Do I notice any differences? Honestly, no.

 

[Twilkes]

That's only 1cm difference though. What about 195mm, or 150mm?

There's a recommendation that at full stretch there should be a slight bend in your leg, for optimum muscle use, but doesn't seem to be a recommendation for the angle of your knees when your foot is at the top of the pedal arc. If there was, this would let you calculate your optimal crank length.

 

[oldfatfool]

Shorter cranks for sprinting, longer cranks for hill climbing/grinding

 

[Mr Haematocrit]

I'm now running 165mm cranks

 

[smokeysmoo]

What about 195mm, or 150

Good luck finding those!

According to crank length calculators I should use 195mm cranks.

IMO, simply no need what so ever.

 

[Twilkes]

Just seems odd that everything else on a bike is adjustable/manufacturable to perfectly fit an individual, but everyone has to use the same length cranks. How can I cycle knowing that the knees of the man next to me go up higher than mine?

 

[smokeysmoo]

Just seems odd that everything else on a bike is adjustable/manufacturable to perfectly fit an individual, but everyone has to use the same length cranks.

Not true unless you had a full bike fitting and a custom bike built off the back of it IMO.

How can I cycle knowing that the knees of the man next to me go up higher than mine?

Er, maybe just get over it! Seriously though, are you racing at a professional level? Are you having knee issues? If not I personally wouldn't lose a wink of sleep over it.

If you are racing, or in pain then maybe you need to pay out for a full bike fitting to see what that shows, but in 39 years of riding road bikes, (geared and fixed) and MTB's I've never used anything other than stock cranks.

 

[black'n'yellow]

Shorter cranks for sprinting, longer cranks for hill climbing/grinding

do you stop and change at the roadside then..? How does that work in races..?

but doesn't seem to be a recommendation for the angle of your knees when your foot is at the top of the pedal arc. If there was, this would let you calculate your optimal crank length.

knee angle is usually adjusted via saddle setback - not by crank length..

 

[Twilkes]

knee angle is usually adjusted via saddle setback - not by crank length..

But then I'll have to adjust my handlebars again.

Oh f3ck it, I'm just going to drive.

 

[black'n'yellow]

But then I'll have to adjust my handlebars again.

why?