Alex_C
I ride 165 on my roadie, 170 on my TT (it came with 170) and my gravel came with 170's. I have a bit of toe overlap and have a spare 165mm Ultegra crank. I prefer 165 on the street because I usually spin in the mid 90's. On gravel, I spin slower and often grind. Has anyone regretted going with shorter cranks on their gravel bike?
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Talabardio
Overall height and/or leg length is frequently correlated with crank length. It seems that shorter persons frequently employ shorter cranks... Is this your situation? There are theories and advocates lined up on all sides of the crank length spectrum, so a coherent response that offers anything more than useless anecdotal evidence might be quite hard to find. Having said that, at 179 cm I typically enjoy a 172.5 crank length but have used 170 and found it to be completely fine.
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ljsmith
People love to bust out all these calculations and theories concerning crank length.  In reality there’s so little difference that it’s really not noticeable at all.  I have used 170, 172.5 and 175 and really could not tell any perceivable difference.  Now when I get down to 165(on my wife’s bike) it’s starts to feel a little off but I probably could even get used to that.  If 165 feels good for you, there’s no real downside to using them for gravel.  You’ll have less toe overlap and less pedal strikes if you ride rough terrain.
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mosinglespeeder
agree, not a huge difference, I run from 170mm on road for spinning, to 175 on mtn bike singlespeed.  The 175 gives a bit of leverage and you will note not spinning as easy but you better be able to crunch a gear on hills.  So probably similar from 165-->172.5
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chas
It really depends if you want to spin or grind.
I use 167.5 on my track bike (<150rpm) because I need the horsepower and I'm fixed gear.
I use 175 on my tandem and MTB because I need the torque at lower rpm.
Road and Gravel are in the middle for me (170mm & 90-100rpm)

I'm just guessing, but if your grinding you probably don't want to go shorter.  
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Slim

While I agree with Chas points about spinning vs grinding general, we have to look at the amount of change we are asking about.
170 > 165mm is 3% change. So, even if there was an absolute hard and fast rule, it would still just mean you’d have to have a 3% change in cadence...

On an anecdotal note, I switched from 175 to 170mm cranks on my mtb and do not notice a difference. I am 6’5”, so 170 is very short in a relative sense.

I have never come across research indicating a big difference in power with crank length changes in the normal realm.

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ccand51997
Over the past 15 years I have tried 190, 180, 175, 172.5, 170 and 165.  When I started going to 165 for my tri bike I decided to try it on my other bikes and now that is my standard length.  I prefer to spin and put aero bars on all my bikes so the smaller circle is more comfortable.  My inseam is 34.5 inches and I just like the shorter levers.  
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shiggy

My shortest cranks are 180. 182 and 185 on my other bikes. The longest are on my mtbs. 

175 or less feels like walking with my shoelaces tied together. Need the great range of motion in my legs. I do spin in the 90-95 range on the flats, regardless of the bike. Slower on the climbs. I MAY spin a bit lower RPM with the longer cranks, but my foot speed is about the same (longer cranks = larger circles/ bigger circumstance)

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Alex_C
ccand51997 wrote:
Over the past 15 years I have tried 190, 180, 175, 172.5, 170 and 165.  When I started going to 165 for my tri bike I decided to try it on my other bikes and now that is my standard length.  I prefer to spin and put aero bars on all my bikes so the smaller circle is more comfortable.  My inseam is 34.5 inches and I just like the shorter levers.  


I feel the same way. 165's are my preferred length. Better position and cadence. I'll be switching to 165 on the gravel bike.
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Alex_C
Thanks for all the posts. The consensus seems to be 'ride what you like'.
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