Crank length

[nagden]

I am looking for a new chainset. I have always had 170mm cranks. The chainset I would like is only available in 172.5 mm. I would like to know if this extra length would make much difference. Thanks in advance.

 

[Milzy]

It’s better to go down than up. If you don’t care about bike fit then go for it.
I’m on 170 by a bike fitter but new research says I could benefit from a 165mm.

 

[Jameshow]

How tall are you?
If average or above height it won't make a difference imo.

 

[fossyant]

You'll hardly notice. 170m on 3 bikes and 175's on two others (MTB's)

 

[presta]

The differences in crank lengths have always struck me as pretty insignificant TBH, although I'd expect people with shorter legs to notice more than the long legged. It's lowering the gear ratio, but only by the equivalent for going from a 33t sprocket to 34t. If you're going longer, a point to watch for is toe overlap, although 2.5mm isn't much. My toeclips just touch the front mudguard, and I suspect if I were to increase the cranks by 2.5mm the mudguard would flex enough to avoid anything untoward happening in the event of any conflict.

 

[Sharky]

If you change one of the variables in the transmission set up (crank, chain wheel, sprocket, wheel size), the laws of physics will apply and there will be a difference, but so small that you would not notice.

If your saddle height is critical, you may want lower by 5mm.

Ive gone from 170mm cranks to 150mm and I did feel the difference.

 

[nagden]

Many thanks for all of your useful replies. I have now ordered chainwheel with 172.5 cranks. I will let you all know how I get on.

 

[fossyant]

Many thanks for all of your useful replies. I have now ordered chainwheel with 172.5 cranks. I will let you all know how I get on.

I did wonder when my MTB needed a new crankset (ended up cheaper for a whole crankset) and I was moving to 175 from 170. Didn't notice. Then bought another MTB, and that was 175 too.

I do tend to stick to 170 on the three road bikes as all are more or less identical on the 'fitting' and makes swapping fine.