going shorter crank length - any regrets

[cuda]

currently i'm on 172.5 on a 55/56 frame. I'm 180cm with a 86cm inseam.
I consider myself fairly flexible and in good shape for my age(65).

I was previously riding 170's but with my new build focused on climbing I decided to bump up the crank length a tad, plus I got a too good to pass up deal on the new crank. After a solid month or so on the trainer dialing in my fit I'm still getting a slight of pain at the top of my right knee. I can also feel a bit of hip flexor impingement on the same leg so I'm lead to believe they are related.

I'd hoped that a bit more flexibility and core exercises might remedy the knee issue. I also tilted my saddle nose down 3-4mm (just shy of feeling more weight in my hands on the hoods)
Its sort of working but I'm impatient so there is that. Over the weekend I did a deep dive into moving to a shorter crank length. It would seem the trade off are net positive mainly due to opening up hip angle.
I'm trying not to go too far with the change as to not impact other aspects of my fit. It seems that -5mm will be an improvement? - (172.5 - 167.5)

I'm pretty sure this plus continuing with my stretching and core work will be a win but I'm still slightly on the fence.

so the question i have is if you have moved to shorter crank arms do you have any regrets? In particular climbing.
thanks

[Flinch]

Went from 175 to 170, then liked it so much that I went to 165mm - never looking back!

No knee issues, fixed my asymettrical hip problem, I spent two weeks last fall climbing 15-20% grades in the UK on a loaded mountain bike.

Do it.

[Mark McM]

I'm 169mm tall (inner leg length 82cm), and I moved from 170mm to 165mm 2 years ago. I don't have any regrets, but I do have one caveat: In order to compensate for the shorter lever arm of shorter cranks, you also need to lower your gearing. The conventional wisdom is that the lower torque generated by shorter crank arms can be compensated for with a higher cadence. Which works fine in the middle gears, but in order develop a higher cadence in your lowest gear, you need a lower low gear. Otherwise, climbing with the same gear but with shorter cranks actually requires more leg force.

[Likes2ridefar]

165mm for me and no regrets going shorter. I’m 6 feet tall. It was an easy change and on the mtb from 175 to 165 made the difference in sore hips or not.

[helldriven]

Totally agree with all replies so far, I have 160's on one of my mtb's and have found no downsides. Like Mark McM has stated you may have to adjust your gearing. I believe there are numerous studies out there that have found no power loss with going shorter (within reason).

[Spoker]

Do you increase the seat height with the shorter crank?

[Alexi]

Around 15 years ago I did a fitting with John Allis, and he said I could go up a size on my cranks, I was running 167 on the track and 175 on the road and mtb. I’m 5’11, and he thought it was weird but I might be happier with longer cranks.

I stuck with 175. Ended up on 170s on a road bike around 10 years ago due to me ordering the wrong size for my Spooky. I just ran with it and have been happy.

I’m now running 170 on one gravel bike, one mtb, and the fixed, 165 on the other gravel and mountain bikes. I want to go to 165 on everything eventually.

[cuda]

Originally Posted by Mark McM

I'm 169mm tall (inner leg length 82cm), and I moved from 170mm to 165mm 2 years ago. I don't have any regrets, but I do have one caveat: In order to compensate for the shorter lever arm of shorter cranks, you also need to lower your gearing. The conventional wisdom is that the lower torque generated by shorter crank arms can be compensated for with a higher cadence. Which works fine in the middle gears, but in order develop a higher cadence in your lowest gear, you need a lower low gear. Otherwise, climbing with the same gear but with shorter cranks actually requires more leg force.

Thanks Mark, Did you change front chainrings or cassette? Both? I'm currently running 52/36 with an 11-30t. There is not many climbs around me over 12% and those are more of a punchy vs sustained effort. When I was on 11spd the rear was 11/28. I seldom if ever needed it. That said I would like to do some travels to better near by climbing regions.

[Likes2ridefar]

Originally Posted by Spoker

Do you increase the seat height with the shorter crank?

Yes mine was exactly the change of the crank length. On both 1x axs mullet gravel and 1x mtb I did not change or notice any gear/ratio change other than my cadence being slightly higher consistently. I shortened length by 7.5mm on the gravel and 10mm on the mtb.

[Mark McM]

Originally Posted by Spoker

Do you increase the seat height with the shorter crank?

I did. When I reduced crank length by 5mm, I also increased seat height by 5mm. By simply moving the seatpost up, it also increased saddle setback by about 1.5mm, partially compensating for the shorter forward extension of the crank.

Depending on how much you move the saddle, you might also want to re-adjust bar height as well.

[Dave]

If a knee feels tight at the top of the stroke, be sure that your saddle height isn't a bit low. Since I came back to cycling with new knees, I've used 172.5 crank arms like I did for many years, then tried 175 for one season since I climb a lot, then went to 170 to help out a tight right knee. My cycling inseam is 83cm. Last year I had some sharp pains behind my right knee and tried raising my saddle height by 10mm, that eliminated the problem. I later dropped it about 3mm. The added saddle to bar drop didn't bother me and mine is over 11cm.

I'm done with crank arm length changes.

[Mark McM]

Originally Posted by cuda

Thanks Mark, Did you change front chainrings or cassette? Both? I'm currently running 52/36 with an 11-30t. There is not many climbs around me over 12% and those are more of a punchy vs sustained effort. When I was on 11spd the rear was 11/28. I seldom if ever needed it. That said I would like to do some travels to better near by climbing regions.

In my case, I changed from a 52/36 semi-compact crank to a 50/34 compact crank. That decreased the high end gear by 4% and the low end gear by 6%. I've always been a spinner, so the lower gears didn't effect my top end speed.

[cuda]

Originally Posted by Mark McM

I'm 169mm tall (inner leg length 82cm), and I moved from 170mm to 165mm 2 years ago. I don't have any regrets, but I do have one caveat: In order to compensate for the shorter lever arm of shorter cranks, you also need to lower your gearing. The conventional wisdom is that the lower torque generated by shorter crank arms can be compensated for with a higher cadence. Which works fine in the middle gears, but in order develop a higher cadence in your lowest gear, you need a lower low gear. Otherwise, climbing with the same gear but with shorter cranks actually requires more leg force.

Thanks Mark, Did you change front chainrings or cassette? Both? I'm currently running 52/36 with an 11-30t. There is not many climbs around me over 12% and those are more of a punchy vs sustained effort. When I was on 11spd the rear was 11/28. I seldom if ever needed it. That said I would like to do some travels to better near by climbing regions.

[Jdm]

I spoke to my bike fitter this weekend about this. His perspective on bike crank length is if you have a problem like hip pain and a shorter crank length fixes it, then get shorter cranks. Otherwise, don't spend the money on new cranks.

I ride 165mm on my road bike and 172.5mm on my gravel bike because that's what came on both. I fit both and all of my rides have a ton of climbing.

One drawback of shorter cranks per my fitter is you're asking your body to do less mobility, which can be a problem as we get older since we want more mobility.

[Tychom]

I've gone from 175 to 172.5mm on road and gravel bikes and from 175 to 170 on the mountain bike. Less extreme than some, but it's overcome some knee pain I was having at the top of the pedal stroke (along with suitable increase in saddle height).

I've only changed the gearing on the mountain bike where there was a noticeable difference when needing to spin up the steepest of slopes. In this case I changed from an 11-46 (11 speed) to 10-51 (12 speed). And there's the bonus of less pedal strikes too.

Can't say I've had any regrets.