When I made the change to my main road bike I waited to see if the change was to my liking before doing anything else. Once I was certain I put 165’s on my gravel bike and a set of 170’s I had put away for my indoor bike. Yes it could get quite expensive but I’d say it is worth it to have your bikes not forcing big changes physiologically when going from one to the other.
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Put me in the “meh” crowd. Went from 175, to 170, then 165. I always struggle with lower back pain, especially when spending time in an aero position, so was hoping for improvement.
Didn’t really notice much difference, and also felt that sometimes I was missing some ability to use torque when I wanted to. But nothing strong enough to feel confident in whether it was an actual difference or just unreliable “feelings”.
I’ve settled on 170 for now on both my road bike and gravel bike. But, yeah, just kind of “meh”.
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I run 170mm and changed all bikes to be the same. I have two gravel bikes (older one on the trainer) and a mountain bike. I had to change all three as the Gravel bikes were 172.5 and Mountain Bike 175mm. I think it is good to have them the same.
Just got a new mountain bike this last week which I had to do a couple rides on 175’s until I was able to swap. It reconfirmed that I really like 170’s but I don’t think I am ready to jump to 165’s at 6’ tall.
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This is why I haven’t tried it. I’m afraid I’ll like it.
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No, just my road bike to 167.5. But the others are 170 (MTB) and 172.5 (Gravel).
I don’t notice it on my MTB cause it’s just such a different bike. But I do notice it on my gravel bike. But that’s probably only like 30-45% of the difference since the seat angle and saddle setback are both a bit more slack/further back as well.
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A couple years ago I went from 172.5 to 167.5 on my road bike. It was certainly a positive change that I recognized from the first ride. All I changed was I moved my saddle up ~5mm to compensate. My pedaling felt a little smoother, my knee didn’t hit my stomach as badly when I was in an aero position, and it felt like I was more ‘on top’ of my pedal and doing less pedaling forward.
But after like 2-3 rides I didn’t notice a difference and it was all normal. Still good and better but not so revelatory that I thought about it on every ride.
I do sometimes think that going a bit shorter could be better (especially since I ride with my saddle all the way forward with a zero offset seat post) but what I have is good enough for me now.
No regrets here going 172.5 to 165. Pedalling wise I can’t say I notice a difference (and switch between the two), but can definitely notice in an aero position and am more comfortable.
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I only changed them on my MTB. My trainer bike (the only other one that gets appreciable ride time and also a MTB but a hardtail) still has the 175s that came on it, though I do plan on switching those out with some 170s I have laying around (don’t want to buy a new crankset to get 165s). The swapping back and forth doesn’t feel odd to me. Cadences are a bit lower indoors versus out, but I seem to adjust without issue. I prefer the shorter, but don’t mind the longer inside since my rides aren’t as long.
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To add to that, my hardtail has 175 mm cranks on it, and the length difference is something I immediately notice and dislike. For a minute or so my pedal stroke feels “unround” when riding the larger MTB crank. Never have a problem going down in size.
I got a custom gravel bike and they put me on 172.5 (from 175), and I love it (6’3"). I took a long ride on the old road bike with 175 and my hip was hurting for weeks. Some more anecdata to support that shorter can help. I’m also a bit dumbfounded the 2.5mm could really make such a difference, could be something else about the fit.
I actually don’t really notice tbh. Different frame geometries on the different bikes so it’s never a true like for like with just crank differences.
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Pretty sure I’ve told this story before. As a teenager I put 115s (from a small child’s bike) on my cheap mountain bike which had 26" wheels & originally 165mm cranks. Was weird at first, took a few rides but then got used to it. Then got back on my road bike which had 170s which then felt weird but of course in the opposite way. After a couple of weeks of alternating, the weirdness only lasted a few minutes at a time.
Wish I had a photo of that bike, it was just absurdly silly. 
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Went from 172.5 to 170, then down to 160mm.
No regrets, super comfortable and a huge difference in hip stability and whatnot.
Way easier to hold aero position for longer times. No difference in power.
Climbing is also way, way more comfy due to reduced hip angle while climbing. Almost feels like riding on the flat, but uphill.
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I started going shorter 5 years ago based on the discussions on Slowtwitch, I put 165s on my TT bike. Slowly I have shortened my cranks on all of my bikes. No regrets at all. I used to ride 172.5 on everything. I do shout out to the slowtwitch forum for being like 10 years ahead on every major bike trend of late (aero, wider rims, tire rolling resistance, and short cranks).
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I just switched to 155mm cranks on my TT bike and love it. I’m tempted to buy a set down the line for my road bike that has 165mm. It’s a good bit more comfortable, especially since I’m on the shorter end at 168cm.
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Transformation change for me,
- So much easier to spin my heavy carcus up the steep hills.
- Better comfort on the bike.
- Slightly faster cadence on the flats.
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Went from 175 and 172.5 (mtb and road/gravel) to 165 on all my bikes. For my height I have relatively short legs. I really like the shorter cranks. Literally for decades I used to have issues with the left knee when ramping up training volume during the year. This has vanished. I probably could do well with even shorter cranks.
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Total opposite for me. Going from the 170mm on my gravel to the 175 on my enduro feels so good.
But, also, everything about my Enduro feels so good, so 
I don’t notice a difference in my roadie at 172.5, though it is very comfortable. I think it’s partly that I prefer a steeper STA.
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I’ve got a significant leg length discrepancy (c20mm) and I put 6mm of shim under my cleat…really works a treat!!
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This is a good example that shorter cranks may not be for everyone. I agree that they can have benefits for many but clearly not all. Even in my own experience long cranks (175’s) were always fine, even in my multisport days of riding an 80 degree seat angle tri bike but I do run shorter now just to ease stresses on the knees but I do wonder sometimes as climbing seems much more stressful with the greatly reduced leverage. But that is a very small percentage of my overall mileage so I’ll stick with the 165’s
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