squatchy

I want to replace my standard crank to a compact. I now use 175's and was wondering if I would even be able to tell if I bought one with 172.5 crank arms?

gregf83 

Probably not, although you should raise your seat 2.5mm.

clausen

When I went to a smaller crank arm length, I did not notice it except that I found I can spin better.

datlas 

You may be mixing up terms. Compact crank means the gears are 50 and 34 tooth, versus standard 53/39.

Obviously that is a significant difference.


OTOH if you mean a shorter crank, I doubt you will notice a difference of 2.5 mm.

Campag4life

I can feel a 2.5mm crank arm length difference FWIW. 2.5mm = 5mm diameter difference and the distance your feet travel in a circle is Pi * D.
BTW I ride 175mm cranks and love them.

shelbyfv

I have two bikes with similar Ultegra cranks. One is 175 and the other is 172.5. I cannot tell one from the other.

FatherAlabaster

I am 6'2" with long legs and a shorter torso. The added range of motion when I went to 175s was slight, but immediately noticeable. For me, it was a big improvement. I've considered trying 180s but I already have knee problems from work, and no money to put into the bike right now.

garciawork

I feel that I am in the minority, but at only 5'10", the move from 172.5 to 175 was VERY noticeable, in a very good way. I can't ride bikes with 172.5 anymore. I actually needed to bring my cadence down from 120 though, now I am closer to 110-115 in the flats, and I also have that little bit of extra torque when standing. Makes me curious about 177.5's...

Elduderino2412

i went from 172.5 to 175, and i could tell a difference. Of course that may have just been mental

rat fink

I notice a difference in crank arm lengths. I feel most natural with 170s. 172.5s are okay. Currently, that is what I have on all my bikes. But 175s don't feel quite right, and occasionally, I feel it in my knees. Note that these differences are subtle, and only manifest themselves over an extended period of time.

cvall91

When I got my new bike, I went from a 172.5 compact to 170 standard. My old bike was a 56 and went down to a 54. I wanted to get a 172.5, but really didn't know the difference besides the physical size. First ride out, apart for my new found love for standard cranks, I realized I was spinning faster at the same effort. As in, what I felt at 95 cadence would be what I was now feeling at a little over 100 cadence. Could be mental, but that's my experience.

svtmike

I have one bike with 172.5 cranks and the rest with 175. I wouldn't be able to tell the difference in a double blind test.

I think that I self-select a marginally higher cadence with the marginally smaller cranks though.

pallen

Some people claim to be sensitive to it. I have bought 172.5 and 175 cranks in the past. I couldnt tell you what is on which bike right now. I dont remember and they all feel basically the same.