[Closed] Changing from 175mm-170mm cranks. Good idea?

I noticed a difference going down to 165s but I've got a mix of 175 and 170 on all the bikes now and tbh I can't tell any difference. I could take a guess which cranks are on which bikes though.

How many bikes, Northwind? I seem to recall you replying to threads on singlespeeds, roadrats, 29ers, Souls and Ragley Tis - and I know there's a Hemlock and an Orange....

10mm lighter!

honourablegeorge - Member

How many bikes, Northwind? I seem to recall you replying to threads on singlespeeds, roadrats, 29ers, Souls and Ragley Tis - and I know there's a Hemlock and an Orange....

Not all at the same time 🙂 Never owned a 29er though.

Shorter cranks can be a good idea if you suffer from knee pain, you clip your pedals frequently, or you're not very good at spinning and want to improve your technique.

They can also be a wise move if you're shorter in the leg than average.

But it's largely personal preference. I've got slightly longer legs than average and I prefer 170's. I can tell the difference myself, though only slight, but then I used to suffer badly with knee pains and 170's went some way to stopping that.

I do suffer from quite a bit of knee pain. How do shorter crank arms help this?

I have both and can't really fell the difference. Swapping definitely reduced pedal strikes on my Reign though

I've tried them as it was suggested they might benefit me in terms of fit but I just 'felt' down on power all the time – whether or not I actually was, who knows but it didn't feel nice. Still got them on one bike and I hate riding it – should probably swap them out 😐

You will never know !!!

I went from 170 to 175 on my road bike, and I do notice a difference at the top of the stroke, my body position just seems to all get a bit too tight and restrictive. But I am fine with 175 on my mountain bikes, so make of that what you will. I will be changing my road cranks back to 170 when I can afford it.

Don't think I would have noticed going the other way though.

Don't notice 172.5 road to 175 MTB, but do notice 165 on the track

One bike is 170, the other is 175. I can't tell the difference.

I do suffer from quite a bit of knee pain. How do shorter crank arms help this?

Smaller diameter circle that your feet go through means less bend at the knee per rotation. You may think 10mm (5mm per crank and crank arms being opposing in direction add the difference together) makes very little difference but it makes more than you think it might!

Or it may make no difference at all... It's one of those divisive subjects, some people swear blind on having a certain crank length, some couldn't care less.

Maybe I'm just getting desperate as I'm looking at getting some new cranks and they're a bargain. I already feel 'down' on power so maybe it's not the best move?

How short are your legs, as if you have longer legs than normal it could bring other issues.

Used 175mm for years on XC and road bikes, when my riding headed towards more downhill I swapped to 170mm. Never noticed a difference in power or comfort, but did notice less pedal strikes.

Inside leg about 33 inches so I don't think I'm a shortarse.