Shorter Cranks

[daninplymouth]

Hi, not sure if this is in the right section but i was after feedback on anyone who has gone shorter on their cranks.
I'm about 192cm currently riding 175mm when I had my bike fit I was recommended going shorter, the fitter is a big fan of this but he knows his stuff and I trust what he says. I would probably benefit more too as my flexibility isn't the greatest.
I was thinking of going down to a 170mm would this be noticeable? I understand I'd make slightly less torque but cadence would increase however not sure what the full effect would be as I'm currently riding a 50/34 and want to go up to a 52/36

[moock]

I am 1,90m and have long legs. I always had 175mm cranks. Once I tried 172,5 for a year or so, and I did not felt any difference.
Then I went back to 175 cranks and i was instantly faster and it felt 10x more efficient.

[Lucendi]

You will most likely not notice any difference between the 175 and 170 mm crank. What you gain in leverage you lose in cadence.

You will have to raise your saddle 5mm though.

[wltz]

I'm 178cm / 5'10" and I've gone progressively down 172.5-170-167.5-165. I've never looked back. My average cadence has stayed the same more or less (when cruising / tempoing I revert to my natural range), but I can maintain a higher cadence at threshold, which is what matters. What has changed is I'm not getting any knee pain from overuse. Dialling in the saddle position can take some time, but is worth it in my book. I would say you can feel 5mm of difference, I still have 172.5 cranks on my "turbo" bike just because I'm lazy, and the difference is noticeable.

[daninplymouth]

Would the shorter crank make first gear feel harder due to the decrease in torque? Or as it should be easier to spin would that make it feel easier? I prefer to spin more on the hills rather than grind a gear out but we have quite a few big hills around me

[ghostinthemachine]

Just search for 165 or short cranks on the forum, there are 3 or 4 that i've found, and one that is currently running.

I'm on 165, though i'm not as tall as you. A slightly larger cassette (or smaller rings) accounts for the trade off between cadenace and torque.

[BigBoyND]

Would the shorter crank make first gear feel harder due to the decrease in torque? Or as it should be easier to spin would that make it feel easier? I prefer to spin more on the hills rather than grind a gear out but we have quite a few big hills around me

Usually foot velocity is what naturally remains constant. When you switch to shorter cranks, rpm rises roughly proportionately. So yes, it will affect gearing accordingly. 175 cranks with 53t ring will feel like 165 with 50t ring.

I'm 191cm/6'3" and have gradually gone down in length until I landed on 170mm for both TT and road.

[Hexsense]

I was thinking of going down to a 170mm would this be noticeable? I understand I'd make slightly less torque but cadence would increase however not sure what the full effect would be as I'm currently riding a 50/34 and want to go up to a 52/36

Ping to this reply for full length analysis viewtopic.php?f=8&t=168105&start=15#p1718120
But if you want to go up in chainring size, shorter crank is not helping it unless it allow better biomechanical posture.

On the mechanical side, reduce from 175 to 170 will cost you almost 3% of torque but raise your natural cadence up by 3% without trying.
That by itself means if you want to feel the same resistance on the pedal you'll use 3% lower gear (from 50 down to 48) and spin 3% faster.

You can also go up to 52 if you really want, but then get one gear smaller in the back than cassette you are using.

[fsp15923]

I'm 178cm / 5'10" and I've gone progressively down 172.5-170-167.5-165. I've never looked back. My average cadence has stayed the same more or less (when cruising / tempoing I revert to my natural range), but I can maintain a higher cadence at threshold, which is what matters. What has changed is I'm not getting any knee pain from overuse. Dialling in the saddle position can take some time, but is worth it in my book. I would say you can feel 5mm of difference, I still have 172.5 cranks on my "turbo" bike just because I'm lazy, and the difference is noticeable.

Hi, I am same height wity 172.5 crank, looking to move to 170 but I would like to know if there was a noticeable difference in power output?

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[Andrew69]

I'm 178cm / 5'10" and I've gone progressively down 172.5-170-167.5-165. I've never looked back. My average cadence has stayed the same more or less (when cruising / tempoing I revert to my natural range), but I can maintain a higher cadence at threshold, which is what matters. What has changed is I'm not getting any knee pain from overuse. Dialling in the saddle position can take some time, but is worth it in my book. I would say you can feel 5mm of difference, I still have 172.5 cranks on my "turbo" bike just because I'm lazy, and the difference is noticeable.

Hi, I am same height wity 172.5 crank, looking to move to 170 but I would like to know if there was a noticeable difference in power output?

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Torque, yes
Power, no (as explained above, a natural increase in cadence will make up for the lower torque output)

[robertbb]

Shorter cranks are almost always better, right up until they aren't

My advice would be to try in increments, and keep going shorter until it feels "off". I realise this may be costly, however.

This is based on my experience as follows:

I went from 172.5 to 170 (having read and watched all about this trend) and most certainly did feel a difference. Loved it instantly. Tried going back to 172.5 and felt like I was on a penny farthing. And this is after 15 years riding on 172.5's because, for the most part, that's just "what most people ride".

After the 170's I then tried 165's as I thought it would be worthwhile to find out if further improvements to feel could be had. My cadence did go up, and notably, my heart rate went down for a given sustained power. There really is a metabolic advantage to shorter cranks in endurance efforts that's for sure. However, I noticed it didn't feel as fluid as the 170's. It was like running with my shoelaces tied together. I never really looked at the data to ascertain if there was a sprint (dis)advantage so I can't offer anything there.

I'd have loved to try 167.5's and that may well have been a good compromise but that length is quirky and not as widely available so I've settled on 170's

For reference I'm 178cm with an 84cm inseam.

[wltz]

Hi, I am same height wity 172.5 crank, looking to move to 170 but I would like to know if there was a noticeable difference in power output?

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Power output as in peak 1s power or average numbers? Conventionally you give away some of your top power by going shorter cranks. If my PM numbers are to be believed, I could hit 1200W max on 170mm cranks for 1 second, with 165mm cranks that's down to 990W. But my 5s, 10s and 15s power numbers are all higher now. I'm not a sprinter nor a crit racer, my game is long distance, and in it shorter cranks make a difference. FWIW I can still start off the lights on 50-11 on a good day, if I am feeling playful.

[MarginalChains]

I'm 175cm and run 170mm on my road bike and 160mm on my TT bike. Tried progressively shorter cranks when I had my TT bike fit, and was able to keep the power while allowing a better fit.

Now I happily switch between the two and barely notice it. 170mm sounds short for someone your height but I'd trust your fitter, and if it feels alright, go for it.

[fsp15923]

I'm 178cm / 5'10" and I've gone progressively down 172.5-170-167.5-165. I've never looked back. My average cadence has stayed the same more or less (when cruising / tempoing I revert to my natural range), but I can maintain a higher cadence at threshold, which is what matters. What has changed is I'm not getting any knee pain from overuse. Dialling in the saddle position can take some time, but is worth it in my book. I would say you can feel 5mm of difference, I still have 172.5 cranks on my "turbo" bike just because I'm lazy, and the difference is noticeable.

Hi, I am same height wity 172.5 crank, looking to move to 170 but I would like to know if there was a noticeable difference in power output?

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Torque, yes
Power, no (as explained above, a natural increase in cadence will make up for the lower torque output)

Thanks but what is your blade sizes? Mine is 52:39. With the imminent move to 172mm crank, I was thinking of a change from 39 to 36 as well. Any difference in torque versus power in this instance? Cadence will increase and climbing should improve though. Any thoughts from those who ventures this route?

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[fsp15923]

Hi, I am same height wity 172.5 crank, looking to move to 170 but I would like to know if there was a noticeable difference in power output?

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Power output as in peak 1s power or average numbers? Conventionally you give away some of your top power by going shorter cranks. If my PM numbers are to be believed, I could hit 1200W max on 170mm cranks for 1 second, with 165mm cranks that's down to 990W. But my 5s, 10s and 15s power numbers are all higher now. I'm not a sprinter nor a crit racer, my game is long distance, and in it shorter cranks make a difference. FWIW I can still start off the lights on 50-11 on a good day, if I am feeling playful.

Thanks, so by inference, the average power increased over longer distance cycling...for me that is anything over 100km. Short of not knowing your setup, its hard to compare wiith what I intend doing. I guess I will have to venture and find out for myself.

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