I have joined the 165 club

[Webbo2]

But if you look at it from the other direction, if your crank was extremely short, say only 1cm long, it would be incredibly stiff to push and logically lengthening the stroke would increase your mechanical advantage and make it possible/easier to turn the cranks.

Combining these two approaches we can conclude that the ideal crank length will be ... somewhere between extremely long and extremely short.

I read somewhere that if you aren’t able to pedal at a high cadence when climbing. You will need lower gears if you go with shorter cranks as you will no longer have the torque you get with long ones.
When on the turbo I can pedal at 90 to 105 revs depending on the gear. But out on the road when I hit the climbs my revs drop dramatically. I can usually out climb most of my peers despite some of them being a fair bit younger.

 

[midlandsgrimpeur]

I read somewhere that if you aren’t able to pedal at a high cadence when climbing. You will need lower gears if you go with shorter cranks as you will no longer have the torque you get with long ones.
When on the turbo I can pedal at 90 to 105 revs depending on the gear. But out on the road when I hit the climbs my revs drop dramatically. I can usually out climb most of my peers despite some of them being a fair bit younger.

You will need to pedal using a lower gear with a shorter crank due to the decreased leverage, as you suggest. Having switched from 170 to 160 some months back, I gave found the shorter crank is more efficient, higher cadence and less muscular force means no leg stiffness for me after a ride now. Power and speed is the same so no loss there.

I made the switch to see if it helped an ongoing overuse back injury. It genuinely has, I can only assume the decreased leverage and smaller gears puts less pressure through my core and back which has alleviated a lot of the strain. I always used to climb out of the saddle a lot, I have realised this was because I was riding too high a gear and the longer crank had too much leverage so I couldn't turn the cranks properly when seated.

My guess is that a lot of cyclists, even if they feel okay on current cranks, would benefit from going shorter.

 

[Vapin' Joe]

My guess is that a lot of cyclists, even if they feel okay on current cranks, would benefit from going shorter.

I'm sure I would have. I rode with the extremely irritating habit of throwing my left knee out at the top of the pedal stroke, not very efficient and awful looking. Just a couple of centimeters less lift of the leg would have stopped that.

 

[Sharky]

You will need to pedal using a lower gear with a shorter crank due to the decreased leverage, as you suggest.

Agree with everything you've said above, however, if the longer cranks were causing knee issues etc, moving to shorter cranks and eliminating the knee issues, improving aero position, may in fact allow the same gear to be used.

 

[Shearwater Missile]

A very interesting thread. From my experience FWIW. I have three road bikes, two with 172.5 and one with 170mm cranks. These are which each bike came with, despite one of the 172.5mm bikes being advertised with 170mm, as per their sizing chart. It really is like Russian roulette what cranks you get. Having said that, I find little difference to which bike I use, other than the fact one of the bikes is lighter, the carbon one. I do find that if I get out of the saddle a lot I end up with sore hips and lower back. I try to make a conscious effort to stay seated and select a lower gear. This can be on any of the bikes. I am 5`8 and guess that my cranks are too long in some people`s opinion. My body, I also guess, has adapted over the years. Regarding aches and pains, I think that age plays a part and also what I have been doing during the day. Bending and lifting, as in gardening, will hurt my back and and knees far more than cycling does.
So for me the cranks are staying put.

 

[Webbo2]

You will need to pedal using a lower gear with a shorter crank due to the decreased leverage, as you suggest. Having switched from 170 to 160 some months back, I gave found the shorter crank is more efficient, higher cadence and less muscular force means no leg stiffness for me after a ride now. Power and speed is the same so no loss there.

I made the switch to see if it helped an ongoing overuse back injury. It genuinely has, I can only assume the decreased leverage and smaller gears puts less pressure through my core and back which has alleviated a lot of the strain. I always used to climb out of the saddle a lot, I have realised this was because I was riding too high a gear and the longer crank had too much leverage so I couldn't turn the cranks properly when seated.

My guess is that a lot of cyclists, even if they feel okay on current cranks, would benefit from going shorter.

I too used to ride out a lot when I was younger. I now find I tend to burn out if I stand up on the longer hills. However I can still get up some of the shorter double% hills on the big ring (52). Shorter cranks and lowering
gearing for me would probably mean a new bike due to lowering of the saddle and how it would effect the reach.
Given that here in the North York moors you can’t go more than a couple of miles with out tripping over a climb of 20% plus Therefore at some point I will need a lower gear than 36 x 34 but by then it might be time to go electric anyway.😂

 

[teeonethousand]

It's been a couple of months and about 500 miles since I changed mine from 172.5 to 165 - and that has included multi day 60 ISH rides on our recent Edinburgh trip.
I did also move my saddle to compensate. All I can say is I have no aches or pains, other than general tiredness, from any ride. Also I do feel 'in the groove' when getting along and a steady cadence... exc hills. I have never been good at hills, my new crank was also smaller cogs so I do have lower gears and my usual plod up them feels the same. A non length related benefit for me was moving from FSA to GRX cranks

A bunch of it might be psychological but I needed new rings anyway and I am glad I replaced the whole crank.

 

[midlandsgrimpeur]

Agree with everything you've said above, however, if the longer cranks were causing knee issues etc, moving to shorter cranks and eliminating the knee issues, improving aero position, may in fact allow the same gear to be used.

Very true, on flats and downhills when I am on the drops I can still ride bigger gears at a high cadence. It is really just on hills when I am moving a couple of cogs further up.

 

[midlandsgrimpeur]

I'm sure I would have. I rode with the extremely irritating habit of throwing my left knee out at the top of the pedal stroke, not very efficient and awful looking. Just a couple of centimeters less lift of the leg would have stopped that.

I think you are right. I realise now that climbing seated with the longer crank that I would often almost lift off the saddle at the top of the pedal stroke. Sounds like we both compensated for the same thing but in slightly different ways.

 

[JonBuoy]

I too used to ride out a lot when I was younger. I now find I tend to burn out if I stand up on the longer hills. However I can still get up some of the shorter double% hills on the big ring (52). Shorter cranks and lowering
gearing for me would probably mean a new bike due to lowering of the saddle and how it would effect the reach.
Given that here in the North York moors you can’t go more than a couple of miles with out tripping over a climb of 20% plus Therefore at some point I will need a lower gear than 36 x 34 but by then it might be time to go electric anyway.😂

Wouldn't shorter cranks mean that you had to raise the saddle?

 

[midlandsgrimpeur]

Wouldn't shorter cranks mean that you had to raise the saddle?

In theory, but it is slightly dependent on the rider. The advice is raise the saddle by the same amount the crank has shortened and move it back by around half the distance. I only raised mine by 5mm (against a 10mm crank difference) and didn't end up shifting it back as the shortened reach suited me better.

 

[Webbo2]

Wouldn't shorter cranks mean that you had to raise the saddle?

Yes of course.🫣 Which might mean your current set up for the bars doesn’t work.