Shorter crank experiences. Then back to longer ones!

Discuss light weight issues concerning road bikes & parts.
xcnick
Posts: 133
Joined: Fri Jan 21, 2011 5:27 pm

by xcnick

I'd be interested in other peoples experiences trying out short cranks.

I have a short 78cm inseam and have a fairly low saddle height as I pedal quite heel down. I replaced 170 cranks for 165's around 18 months ago off the back of getting a track bike and doing some racing on it. I felt more comfortable on the drops for extended periods and the biggest difference were the shorter cranks.
Once on my road bikes the shorter cranks felt immediately comfortable (saddle adjusted accordingly) and almost like small inclines were less noticable. I stuck with them.

However, for some time I've felt my sprint isn't as powerful as it used to be (put this down to getting older!) and when trying to ride at tempo or a sustained effort I just can't seem to push the pedals with force properly. Also my calves often cramped during a sprint which I never had before. I read a comment on a forum where a guy said if he went too short on the cranks he got that 'shoes tied together' feeling and I couldn't put it better myself!

Anyway, I stuck my 170's back on, lowered the saddle a tad and instantly I feel like I can push the pedals better. Sprint is better. I notice my thigh closer to my chest again but somehow I feel more stable and tend to bend my arms more to relax on the bike.

It's only been a couple of short rides so I'm aware it might be partly psychological! But it does feel good. Other riders experiences would be interesting..... :D

grover
Posts: 1111
Joined: Mon Jul 26, 2004 1:06 pm

by grover

What you've described is my experience too. The correct crank length for you is the one that is the best balance of each of those attributes. I think it has a lot to do with hip restriction. How deep into hip flexion you have to go. Also play a little with your saddle angle. The tilt of your pelvis will also have an effect on hip restriction.

by Weenie


Mr.Gib
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by Mr.Gib

My experience was similar moving from 175 to 170 to deal with knee issues. IMO long term happiness with shorter cranks depends on one's ability to spin higher cadence with power. This takes a certain type of coordination and pedal stroke and not everyone is capable of this or likes to ride this way. I do notice a loss of low cadence and standing power due to decreased leverage, so certain climbing situations and sprints are not as good for me.

My knees are now fully recovered so I put 172.5 cranks on a recent build just to see where I was at and I slightly regret not sticking with 170's. They are just more a bit more efficient in the majority of situations and I am a bit more comfortable in the saddle over longer periods of time with them.
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AJS914
Posts: 1902
Joined: Tue Jan 28, 2014 6:52 pm

by AJS914

My experience is similar to Mr. Gib's.

I had 175s for decades. I tried 170s and loved them. I had to use one easier gear though on climbs and increase my cadence a bit.

I picked up a set of Super Record 172.5s for a great price and I kind of miss the 170s. The difference is only 2.5mm so it's not a big deal but if I buy another new crank I'll get 170s again. I ride a a 12-29 cassette. If I go to 170s again, I'd like to have a 32 cog so I can get the spin up on climbs.

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TonyM
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Joined: Thu Jan 22, 2015 4:11 pm

by TonyM

I have also a short inseam of 78.5cm. Riding now for more than 30 years with 170mm I am not sure I should try to force my body to adapt to the 165mm for example.

11.4
Posts: 1102
Joined: Tue May 23, 2006 4:33 am

by 11.4

You shouldn't have to force yourself to adapt. A different crank arm length will immediately feel odd, but you'll acclimate fairly quickly -- some people never notice a 5 mm difference, others will take a week or two to adjust fully to 2.5 mm.

If one doesn't have a rapid cadence or doesn't have gearing to suit slightly shorter cranks, or if one is falling prey to the lack of cadence that sometimes accompanies increasing age, then a bigger gear, longer cranks, and slower cadence may be better for you. We are each individual experiments of one, and there's no saying one approach is right. European road pros will ride with 100 rpm cadence or higher because they also have the genetics to push a shorter crank at high cadence in a big gear. Plain and simple. The rest of us ride what we can ride. So don't sweat it. Experiment to find what works for you, and expect that after a good amount of riding and training you may well benefit from a different combination. You're always an experiment because your physiology is always changing.

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TonyM
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Joined: Thu Jan 22, 2015 4:11 pm

by TonyM

I am still not sure that my body after almost 30 years of biking 10.000 to 15.000 km per year will like such an experiment...even if my cadence is usually 95rpm or more...

ODC
Posts: 73
Joined: Mon Aug 14, 2017 9:40 am

by ODC

This year i have tried, 172.5, 175 and 177.5mm cranks.
I'm 1m90 and saddle height 81.5cm

I felt a difference with al the cranks.
- With 177.5mm a had got more power but also knee pain
- With 172.5 mm more cadence but i felt like I could not push the power that I wanted
- 175 cranks best of two worlds

morganb
Posts: 485
Joined: Wed Mar 15, 2017 5:30 pm

by morganb

I went down to 165 then 160 then 155 then 150 from 172.5 after joint problems and general health problems left me almost unable to ride and feel faster on 150-155 than I did on 172.5 even after missing almost two years of riding. My peak sprint power is about 100-150W off but my 5s power is much closer and my peak has been steadily going up. My peak speed seems to be pretty close as I already had a very low position and now can get even lower.

11.4
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Joined: Tue May 23, 2006 4:33 am

by 11.4

morganb wrote:I went down to 165 then 160 then 155 then 150 from 172.5 after joint problems and general health problems left me almost unable to ride and feel faster on 150-155 than I did on 172.5 even after missing almost two years of riding. My peak sprint power is about 100-150W off but my 5s power is much closer and my peak has been steadily going up. My peak speed seems to be pretty close as I already had a very low position and now can get even lower.
That's going to a real extreme in crank arm length unless you are extraordinarily short. There's a range of crank arm lengths that typically are acceptable to a particular rider, with one or two offering peak performance. Those lengths tend to taper off around 160-165 mm, and that's for riders with shorter femurs. (It's the femur that's the determiner of crank arm suitability, if anything is. Your calf is just there for the ride, while vertical displacement is driven pretty much entirely by the femur. It's why fitters who are suggesting different crank arm lengths aren't doing their clients any favors when they are matching crank arm lengths to full leg length or, bizarrely in many cases, to calf length.) You may want to revisit issues such as cleat placement and cleat tilt, because joint issues across that wide a range of crank arm lengths are typically caused by other issues and no crank arm length will do it for you.

morganb
Posts: 485
Joined: Wed Mar 15, 2017 5:30 pm

by morganb

11.4 wrote:
morganb wrote:I went down to 165 then 160 then 155 then 150 from 172.5 after joint problems and general health problems left me almost unable to ride and feel faster on 150-155 than I did on 172.5 even after missing almost two years of riding. My peak sprint power is about 100-150W off but my 5s power is much closer and my peak has been steadily going up. My peak speed seems to be pretty close as I already had a very low position and now can get even lower.
That's going to a real extreme in crank arm length unless you are extraordinarily short. There's a range of crank arm lengths that typically are acceptable to a particular rider, with one or two offering peak performance. Those lengths tend to taper off around 160-165 mm, and that's for riders with shorter femurs. (It's the femur that's the determiner of crank arm suitability, if anything is. Your calf is just there for the ride, while vertical displacement is driven pretty much entirely by the femur. It's why fitters who are suggesting different crank arm lengths aren't doing their clients any favors when they are matching crank arm lengths to full leg length or, bizarrely in many cases, to calf length.) You may want to revisit issues such as cleat placement and cleat tilt, because joint issues across that wide a range of crank arm lengths are typically caused by other issues and no crank arm length will do it for you.
I have short femurs for my leg length and short legs for my height, anything under 160 I can ride comfortably. According to the Zinn formula for total leg length I should be between 154 and 159. Either way the short cranks fixed my knee issues on the bike and I have been comfortably riding for a year since.

morganb
Posts: 485
Joined: Wed Mar 15, 2017 5:30 pm

by morganb

Also my knee issues occur entirely within a certain range of bending. Shorter cranks reduced the angle of my knee at the top of my pedal stroke (and the hip angle) and keep me from getting close to the point at which issues develop.

xcnick
Posts: 133
Joined: Fri Jan 21, 2011 5:27 pm

by xcnick

The above posts all very interesting.

Most of the studies (probably not actually that scientific) that have been done basically come to a conclusion that almost everyone would benefit from going shorter. Clearly not the case and any formulas to calculate crank length have to be nonsense anyway.
Seems that short cranks work for riders with physiological problems whereas riders without any issues, like myself, need to find the middle ground. Yeah, I span more with the shorter cranks but did it benefit me? Don't think so. Feel better pushing a lower cadence.
ODC wrote:This year i have tried, 172.5, 175 and 177.5mm cranks.
I'm 1m90 and saddle height 81.5cm

I felt a difference with al the cranks.
- With 177.5mm a had got more power but also knee pain
- With 172.5 mm more cadence but i felt like I could not push the power that I wanted
- 175 cranks best of two worlds
Pretty much what I experienced but with smaller size cranks!
grover wrote:What you've described is my experience too. The correct crank length for you is the one that is the best balance of each of those attributes. I think it has a lot to do with hip restriction. How deep into hip flexion you have to go. Also play a little with your saddle angle. The tilt of your pelvis will also have an effect on hip restriction.
I use a specialized Power which allows good tilt of the pelvis. saddle angle is very very slightly nose down but that's how these saddles are. If I feel like it needs tilting too much then it's a little too high. My hip angle is now more restricted with the 170's but it feels better, weirdly!

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Rick
Posts: 2004
Joined: Sat Aug 29, 2009 4:30 pm

by Rick

33" 83.8 cm inseam.
I used 175s for decades, but I was absolutely certain that there must be a difference and an optimum, so I experimented with 170 and 180.
I was absolutely flabbergasted to discover that I can barely tell any difference, even going directly from smallest to largest, and it made absolutely NO difference (literally zero watts) in any interval tests I was able to repeat....long climbs, short sprints, etc. Sometimes I even forgot which cranks I had on and would start thinking "Oh, yeah these 180s do feel too long." and then remember I was riding the 170s!
I would not have believed this myself if I had not experimented numerous times with switching them out. (I kept saddle-to-pedal distance constant. Raising saddle 5 or 10 mm when going shorter, etc.)

So I left the 170's on and think about how much money I am saving buying the most common cranks that go on sale a lot!

mattr
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Location: The Grim North.

by mattr

Just as another anecdote. I've been running 170s for 33 years and never had the slightest issue with any sort of biomechanical or knee pain.
Got 172.5 when buying a new groupset (3 month wait for 170s).
Almost instant knee pain. Worse on one side. Spent some weeks looking for 170s in stock then spotted some 165s on a local buy and sell page for not much (been delivered on a bike then taken off to put a PM on)

Took one ride to get completely used to them. Everything about them feels better. Can't believe I didn't try them sooner.

Only issue is that I've got 9 more bikes that now need shorter cranks.

by Weenie


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