Crank length. Will I notice the difference.

I bought my Pinnacle Arkose in the right size for my reach. I’m 177cm but long in the body and short in the leg. This means there isn’t a lot of seat post showing nor is there much stand over; however I don’t see these as issues. The bike feels right. However, and I’m not sure if this is psychological, I’m finding my legs feeling empty sooner than in previous bikes.

However, it comes with 175mm cranks. My previous road bike had 172.5mm cranks. Would I notice a difference? The bike comes with FSA cranks so I could be a tart and match the groupset and get some shorter, say 170mm Shimano 105 cranks from CRC.

No.

Some people do, I doubt it would have this difference tho.

I’ve got MTB’s with 170 and 175 mm cranks and a road bike with 172.5 mm cranks…cant tell the difference between any of them but that may be more to do with the lack of sensitivity from the rider than anything else!

If i was buying a bike for DH use or for really rocky, rough stuff riding then i’d consider 165 mm cranks purely to help avoid pedal strikes.

I have a borked knee so I ride on 165 and 175 cranks. I can’t say I notice the difference.

I normally ride 175 but used a 165 temporarily felt like I was pedalling a tiny clown bike suprised it made so much difference to me went back to 175 asap.

Its been asked a lot before but most people dont notice the difference. However, im someone who does. 175 hurts my knees. 170 I’m fine. So much so that I’m not willing to try 172.5 as an experiment.

Its something only you can decide.

read up on this recently [ there was a cheap crank that was longer] Conventional wisdom [ ie riders say ]you wont notice

Science says you will and better to go shorter than longer [ as no downside re injury /hyper extension.
IIRC its to do with the knee angle at the top dead centre

I swapped out my 175mm s/h cranks (bought from quite a tall fella) on my all-purpose bike; now got 170mm. subjectively, less knee strain and general discomfort. YMMV.

I’ve got road bikes with 175, 172.5 and 170mm cranks – I didn’t even know they were different lengths until last week and have ridden thousands of mile on all of them. 🙂

I had a road bike built a couple of years ago and I spec’d 175mm cranks, each time I rode it something just felt odd, then I noticed they’d supplied it with 172.5mm cranks.
Once the correct cranks where fitted it felt right.
Only a tiny difference but I could feel it.

Recently gone from 172.5mm to 170mm on a road bike, feels so much better for me.

I have a long body and short legs.

It’s made enough of an improvement to feel that I’ll probably drop to 172.5mm on the MTB

I’m a similar height and also have short legs, 172.5mm or 175mm are fine for me on road bikes. 170mm felt too short though.

I’d persevere unless upgrading the chainset anyway.

I’ll probably drop to 172.5mm on the MTB

I’m not aware of any brands that offer that length – but Shimano do 170mm and they make the best cranks anyway.

170 for me and I do notice the difference, totally personal of course, but painful knees vs many comfortable miles for the sake of a few mm, I’m happy to be considered less Manly for my slightly shorter cranks…

Doubt you will notice much if anything….

The claimed extra leverage of longer cranks is negated by selecting another gear in most cases…

Sheldon brown has some good stuff on this.

Longer cranks, say 180 instead of 170 need the saddle dropping to make the bottom of the pedal stroke work. So the low saddle and longer crank at the top of the stroke can over bend knees, hence the pain.

Personally, shorter is better for me…. 165 or 170.

I definitely noticed the difference between 175 and 170 on my bouncy mtb. It’s half the difference but IME road bikes can be very “princess and the pea”

Changed from 175 to 165 and def notice the difference. Sure it helps to pedal faster. Smaller circles and all that..

Isn’t there a scientific way to calculate the correct crank length?

I would.

I never have.

Similar dimensions to the OP and I can definitely feel the difference.
175mm gives me sore knees whereas 170mm is fine….tested both on 2 different bikes just to make sure

I have a pair of 155mm. You definitely notice that…

🙂

I ride 165s on all my bikes. I think it makes a massive difference, the position feels all wrong on 175s esp stood up, it’s like my knees are too far apart or something. And my toe hits the front wheel on the road bike with giant tall person cranks. But I am very short.

i hated 170s on the mtb felt ridiculous. on the road bikes i have 170, 172.5 & 175. can’t tell the difference. try it and see.

On the balance of opinion I’ll give it a go.

Let’s see if I can find a CRC code!

I can’t tell the difference between 172.5 and 175, of which there is a variety across 4 bikes. Track bike is 165 and I do notice that.

I’m 170cm with a 29″ inseam and I notice the difference. I like 170. Gets rid of the empty feeling at the top of the stroke.

even 165 is only 6% shorter than 175. It’s definitley worth trying, especially if you’re not a leggy giant, but it’s not the massive jump that some seem to think.

i tried my wife’s 140mm cranks, they were a bit weird. But not terrible.

I’ve ordered them now, cheers all.

Whatever happens they are lighter than the FSA ones!

10 mm is quite a lot in the world of biometrics. You would certainly notice if your saddle was 10mm too high or low, for example.

I didn’t realise until quite recently that my road bike cranks were 172.5mm, so that’s probably a no from me!

hels – Member
10 mm is quite a lot in the world of biometrics. You would certainly notice if your saddle was 10mm too high or low, for example.

we’re presented with a choice that’s limited to 165-175, as if that covers the full range of sizes required.

consequently, we think 165’s are really short, for tiny people.

which isn’t true.

I know somebody who rides 185s ! But it does restrict you, only the more top of the range group sets run to 165mm. Oh dear, condemned to XTR cranks for life…

165 on the road fixed bikes and fixed MTB, up to 180 on the SS MTB, jumping on the 180 after a 165, a little odd, but after a few mins I don’t really notice the difference.

First ride tonight on the shorter cranks; it felt better. I got a load of PRs on Strava.
However:
1. I didn’t increase the saddle height, so the relative drop in saddle height (5mm, but still…) might have helped.
2. The new cranks are apparently quite a bit lighter than the outgoing set.
3. I’ve ridden an hour a night for the last 7 nights (on the MTBs, these cranks are on my CX), so I’m in the swing of things fitness wise.

There could be a load of other factors for PRs.

. I’ve ridden an hour a night for the last 7 nights (on the MTBs, these cranks are on my CX), so I’m in the swing of things fitness wise.

That’s not how fitness works!

I’d not been riding through illness, so being well enough to get out had improved fitness.

I did notice a difference from 175 to 170, I could spin faster. However lots dont notice anything