Would you ride 150mm cranks?

[KermitGKona88]

Really interesting to find out more about this -- I've always assumed I'm a 175mm guy because most of my bikes came with those. Then when playing around with singlespeeds, it became clear that shorter cranks are common for that application and have some 170s set aside to fit someday. And then bought a bike with 170mms and didn't notice for the first few rides.

The idea of helping the old knees is very attractive -- will have to try some shorties soon.

It is the knee thing that intrigues me too.

 

[Mr.Toad]

I've found that shorter cranks work well for sitting and spinning, whereas longer cranks feel better for standing while riding where torque is more important.

I run 180's on my singlespeed, 175's on my gravel/mountain bikes, 172.5 on classic road bikes.

This is my personal experience. I know the current trend is to go short and I think a lot of that has to do with full squish bikes and their tendency for pedal strikes.

 

[Bcxbcx]

I've got 155 on my ebike. All I can say really is, I forgot they were shorter, they work in that situation. My ebike has a ridiculously low bb, and is used mainly for DH type riding.

 

[clubby]

I saw someone on here 98 + section selling some Hope cranks in 150mm

That was me, but they were 155mm.
I’m 5’9 and 30” inside leg.

I had them on my enduro bike for a year, mainly for pedal clearance. Very noticeable at first. Difficult to describe the sensation but they felt very different. Not bad, just different. After 10 - 15 minutes you stopped noticing. Going back to longer cranks felt different again. If swapping bikes regularly then I stopped noticing. If it was a while going back to the enduro bike then I had to acclimatise again. Funnily though, when I had my e-bike, it also had 155mm but they weren’t noticeable. I think the power from the motor hid the disadvantages.

Pros -

Better ground clearance on long travel bike.
Easy to spin fast.

Cons -

Acclimatisation
Less torque. Had to drop two teeth on chainring.

Ultimately I sold them as I wasn’t riding the enduro bike much and going back and forward to longer cranks felt weird. Back on 165mm which is a Goldilocks length for that bike. My new XC bike came with 175mm and they are fine as well. Also have bikes with 170 and 172.5 and doubt I could identify which was fitted in a blind test. However the 10mm drop from 165 to 155 was very noticeable.

Lots of comments above saying “I’m a 175 man”. Interested to hear if those posters have tried shorter or just assuming that because that’s what older bikes always came with regardless of frame size? These days most smaller sizes come with shorter cranks.

At the end of the day, it’s all personal preference. Try them and report back.

 

[greencat]

I think the difference is at the margins. I always used to prefer 175 bitd as they would give that little extra leverage on the near impossible climbs. They are a pain in the ass on some of modern bikes due to lower BBs.

 

[clubby]

I think the difference is at the margins. I always used to prefer 175 bitd as they would give that little extra leverage on the near impossible climbs. They are a pain in the ass on some of modern bikes due to lower BBs.

Yeah but the extra leverage isn’t as important now we have proper climbing gears. Look at old TDF bikes. They have 42x 24 as a lowest gear for alpine climbs. They needed longer all the leverage they could get. We just inherited 175mm as the default size. Mtb gears can be spun much more easily, so a shorter crank makes sense to me. The added benefit is more pedal clearance.

 

[bikeworkshop]

Short cranks are good for sitting and spinning. (Which is efficient hence hpv application)
Long cranks are good for out-of the saddle climbing.

We usually find a compromise.

Your knees will primarily be affected by the force you're putting through them, so higher cadence is better for the knees - and not working too hard
- and shorter cranks will force this, but aren't necessary.

crank arms that are too long are also bad for the knees because you're increasing the angles when you're applying force - but you might notice that at over 175 for your height.

Saddle too far back can have the same effect.

But 150s will be too short unless you want to prove something...

Unless of course you've got a physiological problem you're needing to solve, where they might help...
Or a motor to provide torque when needed

 

[KermitGKona88]

Seems to me out of the saddle climbing is the biggest down side then? So living in one of the less mountainous parts of Norfolk should help with that considerably.

I do cadence ride, as my right knee especially is pretty shot.

I guess the main consensus is really they are not going to do any major harm, so suck it and see...

 

[madjh]

Not with my money.

I´m a XC rider, so not for me. I don´t do enduro o that shor of things, but I don´t like too long cranks, my size is 170 in the 90s and it is still that. Feels good to me.

 

[paton]

There are lots of opinions on crank length..
Geoff Apps says
https://crosscountrycycle.wordpress.com/2014/11/13/crank-length/
Chris Boardman says
“I don’t think anybody’s really messed around with crank length yet because we’re constrained by history. I’d like to see a lot of people using 150mm cranks. All of the physiology data I’ve ever seen says that for an endurance athlete crank length actually doesn’t make any difference. But shorter cranks mean you’re more aerodynamic – if you’re trying to get into a tuck you can get lower because your knees aren’t coming up. So shorter cranks could produce a really big net gain but it’s a fashion thing.”

https://roadcyclinguk.com/gear/chris-boardmans-seven-tech-trends-2016.html

Phil Burt says
There is no “correct” crank length, as there is no appreciable difference in power output between 150 – 180mm cranks
http://velocitysportscycling.com/cycling-myth-busting-from-team-sky/

https://pubmed.ncbi.nlm.nih.gov/11417428/