Negative effects of shorter cranks

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Lina
Posts: 1298
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by Lina

wheelsONfire wrote:
Wed Jun 05, 2024 2:22 pm
At what point does it affect your preferred cadence? No matter how much i ride, i can't get away from the fact that my average is around 80rpm.
I also must admit, i don't really like spinning like crazy. I can do it in short intervals, but i wouldn't want to average at +10rpm.
I went from 172.5 to 170, but i wanted 167.5mm cranks. Only option was 170mm. Not sure if i should buy a 165mm set.
It seems people here are mostly fore shorter...
For me, I only average higher cadence when really putting the power down. On Z2 I'm about the same as with longer cranks. And it won't feel weird. Because your legs will be making a smaller circle so a slightly higher cadence is the same leg speed as the slightly lower cadence on longer cranks.

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rhs2z
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by rhs2z

I've run 165 cranks for the last 3 years (down from 170), it was a huge benefit for me. I have no real complaints with my current setup.

However, I may be getting a new crank. So I'm wondering: might there be any advantage to trying an even shorter crank? (ie, 160 or 155)

Has anyone moved from 165 to shorter? If so, what was the reason and was it an improvement?

repoman
Posts: 43
Joined: Mon Jun 10, 2024 3:28 pm

by repoman

I used a 165mm for a little bit, thought the pedal stroke sitting felt pretty nice but being out of the saddle felt super wonky to me and I couldn't get used to it so I ditched them.

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pdlpsher1
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by pdlpsher1

rhs2z wrote:
Sun Jun 16, 2024 9:09 pm
I've run 165 cranks for the last 3 years (down from 170), it was a huge benefit for me. I have no real complaints with my current setup.

However, I may be getting a new crank. So I'm wondering: might there be any advantage to trying an even shorter crank? (ie, 160 or 155)

Has anyone moved from 165 to shorter? If so, what was the reason and was it an improvement?
I went from 170 to 155 in one shot. I wanted to try shorter cranks and felt that a 5mm is just too small of a change. Sure, 5mm is a start. But to get the full benefit you need a minimum 10mm of change. Now all of my bikes have the 155s.

Leon
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by Leon

I'm 5' 8" and changed on all my bikes from 172,5mm to 165mm a few weeks ago. I also raised the saddle with the same difference in mm. It takes a few rides to get used to the new length. In the beginning it feels like you are riding a kids bike. :lol: But I can spin the cranks more easy. So that feels good! I don't really see a difference in cadans and / or the way my legs put the power down. I'm just a recreational rider btw.

But so far I'm liking it.
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Vespasianus
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by Vespasianus

I recently put on a set of 175 cranks - they were cheap -and was surprised how easier it was to push larger gears. My front rings are 50/34 but I feel with 175's you need to run a 53/39.

On my gravel bike, I went from 172.5 to 165 and again, felt the need to drop to a 38T front ring versus a 40T front ring. For gravel, I like to spin up climbs.

I think moving to shorter cranks is not a possibility because of the gearing changes that have occured over the last few years.

I personally don't think there is an easy anwer to what is best, it is based on the individual and the type of rider they are. Looking at what the Pro's do, meaningless. They do what they do.
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cheapvega
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by cheapvega

I am 5' 9" with a 31" inseam (so ~175/79cm) and debating going from 170 to 160 on my next build. Don't really have any issues with 170 now honestly.

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pdlpsher1
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by pdlpsher1

31.5” inseam and I’m on 155s.


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PeanutButterCups
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Joined: Mon Aug 30, 2021 8:12 am

by PeanutButterCups

Cut from elsewhere.

The difference between 172.5mm cranks and 170mm cranks is... only 1.45%
The difference between 175mm cranks and 170mm cranks is... only 2.8%
The difference between 170mm cranks and 165mm cranks is... only 2.95%

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cyclespeed
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by cyclespeed

PeanutButterCups wrote:
Tue Jun 18, 2024 8:42 am
Cut from elsewhere.

The difference between 172.5mm cranks and 170mm cranks is... only 1.45%
The difference between 175mm cranks and 170mm cranks is... only 2.8%
The difference between 170mm cranks and 165mm cranks is... only 2.95%
Not sure what that proves?

3% sounds like quite a lot to me, especially in cycling where we fine tune things to the 'nth' degree.

And if you consider that cranks basically go from 145 to 185mm, then this is 40mm. This is the 'useable' range that we are talking about.

Then a 5mm change becomes 5/40 = 12.5%. Suddenly not so insignificant......

PeanutButterCups
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by PeanutButterCups

I just thought it was interesting to see the differences in percentages, some might think it large, others marginal at best.

maxim809
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by maxim809

Shortening crank radius by 5mm reduces the pedaling circle diameter by 10mm.

Try changing your saddle height, stem, or even trail by 10mm. I suspect most experienced people on this forum who are really into bikes would absolutely notice a difference if any of these measurements were changed whole centimeter. Try dialing your cleats back or up 1cm.

Even wheelsets of the same family that is 40mm vs 50mm deep can feel very different when run back-to-back in shear.

If you can adjust any of these by 10mm and not feel a difference, and assuming the rider is not dismissing things to fit a personal narrative, then perhaps the rider is simply and truly not sensitive to fit changes by 1cm. Which is fair.

But it's hard to tell if that's a lucky or unlucky situation to be in.

toxin
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Joined: Tue Apr 18, 2023 5:56 pm

by toxin

Going to 170 from 175 didn't feel like a huge change. Mostly noticed it in extreme positions

rhs2z
Posts: 65
Joined: Fri Aug 04, 2017 7:15 pm

by rhs2z

pdlpsher1 wrote:
Sun Jun 16, 2024 10:22 pm
rhs2z wrote:
Sun Jun 16, 2024 9:09 pm
I've run 165 cranks for the last 3 years (down from 170), it was a huge benefit for me. I have no real complaints with my current setup.

However, I may be getting a new crank. So I'm wondering: might there be any advantage to trying an even shorter crank? (ie, 160 or 155)

Has anyone moved from 165 to shorter? If so, what was the reason and was it an improvement?
I went from 170 to 155 in one shot. I wanted to try shorter cranks and felt that a 5mm is just too small of a change. Sure, 5mm is a start. But to get the full benefit you need a minimum 10mm of change. Now all of my bikes have the 155s.
Yea, I think I was actually 172.5 before, so it was 7.5mm change.

At any rate, moving to 165 helped me open hip angle, etc.- very positive change for me. So I was curious: would everything be even better 155? OR is my hip angle already open enough?

Maybe this is something that I just need to experiment with. But I was wondering about other peoples' experiences, just because 165mm seems to be the golden number- I don't know many people who run shorter than that.

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patliean1
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Joined: Wed Jul 19, 2023 4:51 pm

by patliean1

I'm currently debating sizing down from 172.5 for good. Back in the spring I had a 100km event where I ran 170mm cranks, of which I had my best results/performance ever for the event. Too many variables to conclude it was simply the shorter cranks, but I did notice an increase in prolonged comfort (knees and back) in the drops during sustained efforts. Easier to sustain higher RPMs for power too. I'm a 183cm (6 feet) with more arms than legs. Saddle height is around 77cm, of which I did not change for the 170s. And I'm more of a domestique/leadout rider than sprinter.

My problem is: Should I experiment even with 167.5 cranks too? Having a rotation of bikes means Ideally I'd have to upgrade several cranksets. Then again maybe my saddle height is just too high LoL

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