What do u guys think? I’m getting a new bike, and I actually just assumed my old bike was the standard 172.5, but I just measured them now and realized they are 175. If it makes a difference, I’m 6 ft and weigh 162
I just went from 175’s to 172.5 and I can’t really tell. I’m going to try to bump my seat up that extra 2mm and see how that is. I am only riding on the trainer now though, so I don’t know if that would change anything?
I have changed crank lengths quite a bit. Started at 172.5 then 170, now 165. And to tell you the truth, I don’t “notice” a difference while riding with respect to my ability to pedal. Only difference is that I can get more aero–because of changes in my position allowed by the changes in crank length and now I spin faster. It did take me a while to get my fitness up, because my HR averages used to be in 60-80 range, now its in the 80-100 range when looking at the power files.
So, I don’t actually notice a difference while pedaling…but I notice a difference in my performances when analyzing the files (particularly on the TT bike). When I changed sizes on the road bike…I really can’t tell a difference at all at 5mm, so I am guessing you will adapt with no problems to 2.5mm change. The only issue will be if you prefer to go at a lower cadence or ok with going a little higher.
Now I started to ride with a crank length 10mm difference between the road bike compared to TT bike, and I notice no discomfort or issues with pedaling. My power is adjusted just fine.
If your question is “Will I notice a difference?”, that depends on what type of difference you’re talking about. If you’re talking about a subjective difference (what it feels like to you), only you can answer that after you’ve ridden both cranks on the same bike. If you’re talking about an objective difference, then it doesn’t matter what anyone thinks, what matters is the truth. If you’re interested in pursuing the truth, then take the bike to a human performance lab with validated and calibrated testing equipment , and measure your power output with each set of cranks and plot output against various input parameters (eg. heart rate, cadence) using a standardized testing protocol with statistical analysis of data. Extra points for repeat testing and confirmation of previous results.
What do u guys think? I’m getting a new bike, and I actually just assumed my old bike was the standard 172.5, but I just measured them now and realized they are 175. If it makes a difference, I’m 6 ft and weigh 162
No.
No.
Yeah I ride 172.5’s but spent the last few months training and racing on my coaches P5 that had 175’s and didn’t notice it at all.
I agree with the others above me that said you won’t notice a difference. If you do, it’ll be all in your head. It’s like how your car feels faster the first drive after you change your oil.
I went from a 175mm 52/39 to a 172.5 mm 50/34. Totally noticed a huge difference. Prior to switching, I thought I needed a different saddle (trying the Cobb V-Max used to ride Adamo Road on my old bike). My ass was that sore from efforting in aero or in pursuit position…I could take maybe 1hr with no pain. 2 hrs resulted in significant discomfort and anything over that was very uncomfortable. Racing pretty much sucked although the new bike is a rocket. After the switch- I’m back to comfort level like I had on the adamo- Ironman dist, 6 hrs - no problem. Thinking of going down to a 165 now to see if that will allow me to get lower in the front 
I went from a 175mm 52/39 to a 172.5 mm 50/34. Totally noticed a huge difference.
Hmmmm… The OP didn’t mention gearing changes, only a crank length change. I suspect your experiences may be only partially applicable to the OP. But it’s good info nonetheless.
I ride 175mm on my mtb and 172.5mm on my road bike and 170mm on my tt bike. I did do 175’s on my road but 172.5 just feels better. I went to 170mm last year on my tt bike and while there was an adaptation period 170mm rocks on the tt bike. I rode a personal best this year for 40k. FWIW I’m 6’ tall.
I went from a 175mm 52/39 to a 172.5 mm 50/34. Totally noticed a huge difference. Prior to switching, I thought I needed a different saddle (trying the Cobb V-Max used to ride Adamo Road on my old bike). My ass was that sore from efforting in aero or in pursuit position…I could take maybe 1hr with no pain. 2 hrs resulted in significant discomfort and anything over that was very uncomfortable. Racing pretty much sucked although the new bike is a rocket. After the switch- I’m back to comfort level like I had on the adamo- Ironman dist, 6 hrs - no problem. Thinking of going down to a 165 now to see if that will allow me to get lower in the front
Sounds more like an overall fit problem that was partially solved by shorter cranks and changing your chain ring.
I can definitely feel the difference between 175 and 172.5. I typically ride 175 and occasionally demo/rent bikes and can notice pretty quickly the difference in crank length. Can I tell which is faster?? No.
From my experience going up 2.5 is more noticeable than going down. If you do notice a difference I bet it will be favorable rather than un-.
take out your meter stick and check out how big 2.5mm is.
1/10th of an inch.
hard to wrap my head around being able to feel that small of a difference. then again, the diameter of the pedal stroke is really 5mm.
It’s probably all mental, but I typically ride 175mm on both road and tri bikes. When I swapped to 172.5mm to try them out I didn’t like them. Felt like I lost leverage and subjective power. Back on 175s.
I’m 6’1" and 165lbs.
What do u guys think? I’m getting a new bike, and I actually just assumed my old bike was the standard 172.5, but I just measured them now and realized they are 175. If it makes a difference, I’m 6 ft and weigh 162
You might. Went from 172.5mm to 170mm and I noticed it a little bit on the hills. Not much, but I did.
n=1 here but here goes anyhow
on my tri bike and road bike i like to keep the hip angle the same. What that means is that I have to go with 165 on the tri and 175 on the road. For awhile I had 172.5 (road) and simply the feel of pushing on the crank arms felt wrong, and to be honest I think I would rather have 177.5s on the road bike. I’m basically searching for that optimal hip angle with which to torque the cranks. It’s nothing more than a feeling and I’m looking to close it off more. Opposite on the tri bike. The hip at 175/172.5 and 170 was just too closed given my position. I kept going lower and lower seeking that optimal angle from which I could press the pedals in a manner that I felt was most comfortable.
Now onto about an n=8. If this is your tri bike, move to 165s. I have put 8-10 people on 165s now ranging in height from 5’3 to 6’1 and ALL of them have reveled in the new awesomeness of hip openness. Granted I also have them very low up front so opening up of the hip angle was what we were after. On about half of them we also moved to a 54 tooth or (1case) a 55 tooth to counter act the different feeling of the cadence at certain points along the cassette. They just didnt like the feel of spinning that high.
Good luck!
I started out with the standard 170mm lengths on a Shimano Dura crank 2 years ago. Last year, I moved to a Rotor 165mm length, and didn’t “notice” any differenece. This year, I have gone down to a Rotor 160mm length, and I did “notice” and somewhat faster cadence when on the flats. Beyond this soemwhat “faster” cadence, I didn’t notice any other difference. I will be on the 160mm length in Cozumel next month, so I might know more after that.
IMO, a 2.5mm difference is so slight, that you would likely never “feel” it.
What do u guys think? I’m getting a new bike, and I actually just assumed my old bike was the standard 172.5, but I just measured them now and realized they are 175. If it makes a difference, I’m 6 ft and weigh 162
No