Longer Cranks and Fit - Brief Note

[cgates66]

I've previously posted about using 180mm cranks as an experiment (I'm not super tall but inseam measured the spirit level 35.5-36, which suggests using most methods ~180mm, with outliers on either side) beyond 175s; I am aware that short cranks are the current trend, however I wanted to run this out a little.

Seatpost of course has to be lowered by 5mm to maintain the same leg extension compared to 175. I had good results with this and appreciated the slightly longer crank, but I noticed after a while that I felt a little bit "behind" the pedals compared to shorter cranks, which appeared to be a function of a slightly more open knee angle with the cranks parallel to the ground, and this I did not like.

I recently moved the seat forward by ~5mm to close the knee angle a little bit and it made a considerable difference in feel. With this change, the 180s feel very similar to the 175s in general but with a little more "open" pedal stroke due to the slightly larger motion, which I found desirable - it's a very nice feeling for me.

Cycling fit is very personal, but if you've experimented with longer cranks (or shorter), don't forget to fiddle with for-aft as well as up-down with the saddle.

[tv_vt]

Check back after a few months with another report. Been there, done that, and it did feel pretty good at first, but eventually my knees did not approve. And I can't say I noticed any performance gains with the longer cranks. Went into the experiment thinking it might help with climbing speed, but it did not.

[ridethecliche]

My issue with longer cranks happens on the top of the stroke where my hips just don't feel open enough. I've been riding 165's on my road bike for a bit now.

[callmeishmael]

It's horses for courses, obviously, but I believe the current thinking is that there is almost no disadvantage to riding cranks that are (in theory) too short, but ones that are too long can cause all sorts of issues. My bike fitter says he's fitting >90% of clients with 170mm or shorter, and 165mm is his most popular size. I ride 165s or 160s but would happily try 155s if they were a cheaper experiment.

[fmradio516]

Originally Posted by tv_vt

Check back after a few months with another report. Been there, done that, and it did feel pretty good at first, but eventually my knees did not approve. And I can't say I noticed any performance gains with the longer cranks. Went into the experiment thinking it might help with climbing speed, but it did not.

What kind of pain did you experience? Front or back of the knee?

[mstateglfr]

I am 6'5 and put 180mm crank arms on a Black Mountain MC frame that went from being my gravel bike to commute bike. I had them sitting in a drawer, I had bought them probably 2 years prior at the local bike collective- they are from the mid80s and thought itd be cool to see how I like the length difference.

Ends up I dont notice or care.

175mm on main road bike
175 on backup road bike
170 on zwift bike
172.5 on gravel bike
180 on commute bike
170 on a single speed.

I am not refined enough to tell the difference. Its the opposite with saddles- some can hop on anything and not care whereas I really only have 2 saddles I am going to put on any of my bikes at this point because I have tried so many awful saddles.

Its funny what small differences we notice and dont notice.

[mstateglfr]

Originally Posted by callmeishmael

It's horses for courses, obviously, but I believe the current thinking is that there is almost no disadvantage to riding cranks that are (in theory) too short, but ones that are too long can cause all sorts of issues. My bike fitter says he's fitting >90% of clients with 170mm or shorter, and 165mm is his most popular size. I ride 165s or 160s but would happily try 155s if they were a cheaper experiment.

Interesting that 90% is 170 or shorter since so many bikes come with 175mm stock. Obviously thats why fitters continue to exist- stock isnt for everyone.

[zap]

Echo. Been there, done that. I really did not like the 177.5 I tried 20 years ago. Felt congested at the top of the stroke. Quickly went back to 175.

Next crankset will most likely be 172.5.

[Mark McM]

Originally Posted by mstateglfr

Interesting that 90% is 170 or shorter since so many bikes come with 175mm stock. Obviously thats why fitters continue to exist- stock isnt for everyone.

Or that stock isn't really for anyone. It used to be that stock bikes between 48mm and 62mm came with either 170mm or 175mm cranks. But that meant that bikes intended for riders who are 1500mm - 1900mm tall, a size range of +/- 12%, were expected to fit cranks with size range of only +/- 1.5%. It was cheaper and easier to build bikes with only 1 or 2 crank sizes, and most people can adapt to a range of crank sizes, so the bike makers could get away with that.

[LouDeeter]

Originally Posted by ridethecliche

My issue with longer cranks happens on the top of the stroke where my hips just don't feel open enough. I've been riding 165's on my road bike for a bit now.

This. Causes more issues in my hips when I ride a longer crank.

[cgates66]

Originally Posted by tv_vt

Check back after a few months with another report. Been there, done that, and it did feel pretty good at first, but eventually my knees did not approve. And I can't say I noticed any performance gains with the longer cranks. Went into the experiment thinking it might help with climbing speed, but it did not.

Oh I have a couple of thousand miles on them, this is kind of a long-running thing with the objective of using a little broader range of motion (which isn't always good I acknowledge as the torques on the hips and the knees are different / higher at certain points). I can report no specific knee pain, although if something comes up I will acknowledge.

My main point here was that moving the seat around other than just "down" makes a difference - it was something I overlooked previously (didn't even think about it for a long time).

[mstateglfr]

Originally Posted by Mark McM

Or that stock isn't really for anyone.

I may regret this, but I chose the correct word in that post.

The comment was that 90% need 170mm or less. So everyone in the 10% are good. And everyone in the 90% that need 170mm are good.
That is likely a lot of 'anyones'.

[mhespenheide]

I've said this before. I'm sure I'll repeat it again later.

If you go to longer cranks, I think you need to be very patient and spend plenty of time retraining your legs in order to re-establish your cadence. I'm 6'4" and every crank length calculator out there says that I should be on cranks longer than 180mm. When I finally switched up from 175mm to 180mm after more than a decade of riding 175's, it took me more than six months to really be adapted to the 180's. And that included some PT work for my hip flexors and lower back.

After a couple of years on 180's, though, I dropped back down to 177.5mm cranks for the road and I'm very happy with them. They were almost immediately comfortable. So while shorter cranks may be en vogue, I'm still puzzled by the idea that I'm supposed to ride the same crank length (170mm) as someone much shorter than I am. Maybe "shorter" should still be proportional, and I'm riding something "shorter" than those calculators think I should?

[Tandem Rider]

I road raced on 177.5s back in the 80s, crits on 175s and TTs on 180s. Longer cranks were the style, I currently ride 175s because they are readily available in most versions. Interesting side note from the sample size of 1. I bought a new gravel bike 2 years ago, I spec'ed it with 175s, never checked and started riding it. I love the bike, but my knees started hurting when I rode it but the pain went away when I rode my other bikes. I double checked my position, spot on, I then realized that the cranks were 172.5s. I now realize that crank length is a very personal thing that unfortunately, means a lot of expensive experimenting.

[carpediemracing]

Originally Posted by cgates66

Seatpost of course has to be lowered by 5mm to maintain the same leg extension compared to 175. I had good results with this and appreciated the slightly longer crank, but I noticed after a while that I felt a little bit "behind" the pedals compared to shorter cranks, which appeared to be a function of a slightly more open knee angle with the cranks parallel to the ground, and this I did not like.

I recently moved the seat forward by ~5mm to close the knee angle a little bit and it made a considerable difference in feel. With this change, the 180s feel very similar to the 175s in general but with a little more "open" pedal stroke due to the slightly larger motion, which I found desirable - it's a very nice feeling for me.

Cycling fit is very personal, but if you've experimented with longer cranks (or shorter), don't forget to fiddle with for-aft as well as up-down with the saddle.

I've been fighting myself on 175 vs 170 cranks for a long time, since 2008 or so. I've tried many times to move down to 170s and found that it was much harder to race with the 170s. Part of it might have been fitness, but I discovered that I tend to "stomp" on a downstroke to close small gaps in a group. With 170s I had to stomp just a bit harder, or do two smaller stomps, and it seemed to fatigue me more.

However... in the past few years I've started doing track. And I found that I am able to spin up the 170s faster. In addition, when I get uncoordinated due to a ton of lactic acid (think 15-20 seconds into a sprint), I can turn the 170s over a bit more fluidly than the 175s.

So I'm back on 170s to give it a shot, again. I did 170s for the entire winter for maybe the 5th time in 15 years, reverted to 175s because I couldn't race well (and each time my racing jumped a huge notch). This year the racing didn't jump (although it may have been other factors). I will test the 170s this weekend for the first time where other factors should not be a part of it.

("Other factors" was my HR was wacky earlier this year, would not elevate past a moderate level 145 bpm during rides and races in March, and I was constantly out of breath in race or efforts. No longer an issue.)