Today I tested 150mm cranks on my triathlon bike (I was previously on standard 172.5mm cranks), I was very comfortable in a more aggressive position, pretty much same level of comfort I have on my road bike, which is awesome.
Cadence naturally increased around 5-10 rpm.
However I wasn’t comfortable today with my pedal stroke, it just felt a bit harder than with the previous 172.5mm cranks. But as I mentioned, today was only my first test ride with the 150mm ones, and did 3hrs of easy zone 2 effort on the trainer, but for example I couldn’t even imagine doing today the threshold interval workouts I’m doing with other cranks, it felt harder.
I’m 5’9’’ tall (1.76m)
Does it takes time to adapt to shorter cranks? if yes, how long generally?
or if first ride you test it doesn’t work, then it will never work?
I’ve read there are several studies that mentioned that power doesn’t decrease with crank length, so once I get used to these cranks I should be able to hold same power I was doing on the 172.5mm ones?
I’m very interested on your opinion, even better if you had already perform this crank length change.
I don’t have anything other than my n=1, so take it for what it’s worth: I just switched to shorter cranks on my TT bike, from 175 to 165. For reference, most of my riding is on my road bike, which is 175. I didn’t really notice any difference in the actual pedaling, except my self selected cadence is actually a bit lower, like 95 instead of 100 at TT efforts. I’m having a hard time gauging the power output, I got a new power meter with the new cranks and I seem to be ~10w less then using my old cranks. The old cranks are a quarq and they are what I use on my road bike so I am very comfortable/used to the power outputs from that crank (used to switch them back and forth). All that said, my RPE and TT times for the 10w< power on the new cranks are about the same as the old longer cranks. I’m not sure if the powermeter justs reads a bit lower than my old one or if I’m doing a bit less power, I haven’t ridden my TT bike much yet this year.
Someone may have a more scientific answer, just my n=1, hope it helps.
I am about eight weeks in to my switch from 170s to 155s.
I have had essentially no adjustment period to the shorter cranks. I immediately felt more comfortable in the aero position and subjectively, my pedal stroke feels smoother. Maybe because my hip angle remains more ‘open’ at the top of my pedal stroke.
My power has always been a little anemic and I haven’t noticed a change in that. No better, no worse.
There was also an article I read that mentioned “the new position with shorter cranks can ‘feel’ slower initially because the neuromuscular system needs time to adapt”. Maybe this could be the case for bigger changes like the one I tested today from 172.5mm to 150mm?
There was also an article I read that mentioned “the new position with shorter cranks can ‘feel’ slower initially because the neuromuscular system needs time to adapt”. Maybe this could be the case for bigger changes like the one I tested today from 172.5mm to 150mm?
Although you adapt pretty quickly from a practical use standpoint, you may find it takes quite a bit of time to feel truly comfortable. Give it a couple of months - your body might not be use to the higher cadence.
Thanks! will do. Also I only adjusted the saddle from a height perspective, but I’ve read it’s recommended also to move it backward so knee angle is similar as before, will try to see if that helps as well. But makes sense giving it some time before moving back.
However I wasn’t comfortable today with my pedal stroke, it just felt a bit harder than with the previous 172.5mm cranks. But as I mentioned, today was only my first test ride with the 150mm ones, and did 3hrs of easy zone 2 effort on the trainer, but for example I couldn’t even imagine doing today the threshold interval workouts I’m doing with other cranks, it felt harder.
Are you actually measuring your power output with a power meter? If not how do you know you aren’t putting out more power when it feels harder? For what its worth at 6’1" I moved from 175s to 170s and then down to 165s over the past couple of years with no loss in power but a nicely improved position. I’m in my early 60s so maintaining power year to year is almost as nice as improving it.
Does it takes time to adapt to shorter cranks? if yes, how long generally?
or if first ride you test it doesn’t work, then it will never work?
I’ve read there are several studies that mentioned that power doesn’t decrease with crank length, so once I get used to these cranks I should be able to hold same power I was doing on the 172.5mm ones?
I’m very interested on your opinion, even better if you had already perform this crank length change.
after doing a couple of rides with them I posted a time close to my PR in a local TT. no power with the cranks for that effort and they did feel a bit odd…but then when I switched back to 175’s the day after the TT, those felt weird for the first bit too.
later maximal testing on that same TT course with a powertap and the 140’s didn’t indicate any memorable power changes (IIRC, YMMV, yadda yadda…the file is the one used for pg 86 of Chung’s deck…and that raw file is available somewhere on the internets for those looking for a “gotchya” moment! )
I’m 1.83m with a femur sized for a 1.9m dude if that helps contextually.
That’s lot bigger change than the one I did, and you’re taller also. Hopefully after few rides they’ll feel good, it would be a shame to go back considering how comfortable I’m feeling in the TT position now. Thanks
We find that for a rider going from 172.5 - 175mm down to 150 - 155mm cranks, besides the seat height changes, going to a larger front chain ring really helps. Going to a 54 from a 53 will make the muscle “feel” seem much better. I wouldn’t move the seat position back but would consider moving it more forward a couple of mm with the shorter cranks.
I’m also 5’9" and 158 lbs. I’m about 5 weeks into my 150mm crank experiment. I switched from 170mm.
I switched purely from a comfort perspective. I always felt a hip impingement at the top of the pedal stroke so I wanted to try something short. It fixed that and I love how they feel. I can breath better and have a smoother pedal stroke.
I agree with you though. They felt harder to put out watts on. To be fair, I rode my road bike all winter on the KK trainer using an iRide power meter. Didn’t touch the TT bike at all so much of my struggle could have been the change back to the TT bike. 5 weeks ago I installed the short cranks and put the bike on the trainer. At first I could not even come close to the same output in power and I thought I made a huge mistake. Now I’m back to almost the same watts and a higher RPM. I’m looking forward to it drying out and warming up some on the east coast so I can ride outside.
I have my first race in 3 years coming up in 2 weeks and can’t wait.
yeah, seems they just take some time to get used to, glad that after some weeks you were able to put the same power as with previous cranks, hope that happens to me as well!
My case is the same as yours, change was pretty much to get more comfortable in the aero position, and change was awesome, I felt very constrained in the hip with the 172.5mm on the tt bike.
So, did it take you around 5 weeks to adapt and be able to generate same power as with 170mm cranks?
Can you explain the rationale behind the bigger chainring John?
x2. Shorter cranks already increase the effective gearing, and a bigger ring would increase it again.
I agree, I would think smaller chain rings (or a larger cassette) make the most sense. Especially since shorter cranks result in a higher cadence for the same muscle contraction speed. So if you apply the same downward force as the longer crank, to get the same power you need to spin a bit faster. So having gearing that allows you to have a slightly higher cadence for the same wheel speed, makes the most sense.
On the other hand John Cobb probably has some good reason for the opposite.
yeah, seems they just take some time to get used to, glad that after some weeks you were able to put the same power as with previous cranks, hope that happens to me as well!
My case is the same as yours, change was pretty much to get more comfortable in the aero position, and change was awesome, I felt very constrained in the hip with the 172.5mm on the tt bike.
So, did it take you around 5 weeks to adapt and be able to generate same power as with 170mm cranks?
Good luck with the race!
I would say that every ride felt just a little bit better. Now the higher cadence and watts feel good.
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