Crank Lengths

[jowwy]

I've just bought a new set of cranks with a crank length of 170mm to see if they make a difference to my cadence, i prefer to spin rather than grind away, so hoping this will help.

anybody else using shorter cranks??

 

[Profpointy]

Although I'm 6' tall, on my fixie I've settled on 165mm cranks - and do prefer spinning shorter cranks quickly.

No idea if this is "right" but suits.me

 

[jowwy]

Although I'm 6' tall, on my fixie I've settled on 165mm cranks - and do prefer spinning shorter cranks quickly.

No idea if this is "right" but suits.me

i can defo tell there is a difference between the 175's on my 29er and the 172.5 on both the road bikes

 

[JasonHolder]

There is a difference riding shorter crank arms. It is feeling, and not anything measurable.

 

[ColinJ]

i can defo tell there is a difference between the 175's on my 29er and the 172.5 on both the road bikes

I am about to swap the 175s on my Cannondale for 172.5s and I will be amazed if I can feel the difference. I will report back once I have ridden a few hundred miles on the modded bike.

 

[KneesUp]

I've just bought a new set of cranks with a crank length of 170mm to see if they make a difference to my cadence, i prefer to spin rather than grind away, so hoping this will help.

anybody else using shorter cranks??

Are the 170s shorter than the old ones? If you've changed nothing else your gearing is effectively higher in that for a given cadence you'll go faster with the shorter cranks but it will thus be harder work. Surely if you want to spin more you need longer cranks?

 

[jowwy]

Are the 170s shorter than the old ones? If you've changed nothing else your gearing is effectively higher in that for a given cadence you'll go faster with the shorter cranks but it will thus be harder work. Surely if you want to spin more you need longer cranks?

No - longer cranks make the turning circle bigger, shorter cranks lower the turning circle meaning your able to spin quicker. Yes gearing does alter slightly, but as your foot, leg, knee is going through a smaller circle cadence is increased.

 

[JasonHolder]

Not a chance!

If the ratios of the teeth are the same then, for a given cadence the speed will be exactly the same. The difference will be that your feet will do the work over a smaller circle, so hardeher.

Thats nicely written. But the harder working legs simply cannot be measured as working harder.

5mm worth of leverage at 90rpm creating 200 watts or whatever is mickey mouse.

 

[KneesUp]

If the ratios of the teeth are the same then, for a given cadence the speed will be exactly the same. The difference will be that your feet will do the work over a smaller circle, so harder work. That is why people tend to use shorter cranks and a lower gear together.

Of course you're right. I'm blaming morning brain fog! Still if spinning is your aim then shorter cranks don't seem to me to be the answer. They are apparently better for your knees though.