I have one bike with 170 cranks and one with 175. Are there any potential problems with switching back and forth between the two crank sizes?

Thanks.

Nah, no issues.

Yes, for me.

For you, it depends.

Maybe you should switch them so you have one of each on each bike

I kind of like the change. I have one bike with 175, one with 170, and one with 172.5.

If you feel it and don't like what you feel, that is a problem. Otherwise no. One does have to wonder how such a thing happens. Is one bike also much bigger than the other. That could be a bigger problem than the difference in the cranks. If both bikes are your proper size, the cranks shouldn't differ by more than 2.5 mm. Unless you mistakenly bought the wrong crank for a build that you did, of course.

I have 170 on fixed gear. One roadie with 172.5, one with 170, a couple of MTBs with 175.

I like long cranks in the hills, short ones on the flats.

Thanks, it sounds like I shouldn't worry about it unless it becomes a problem.

Both bikes seem to be the right frame size and, as far as I know, have the original cranks. The 170 cranks are on an old Schwinn Le Tour which is about 20 years older than the other bike.

I have 170 on my road bike and 175 on my MTB, no problems.

Ha, I thought this was going to be a thread about leg length discrepancies - i.e. two crank lengths on the same bike!

As others have said, it's very common for the same rider to use different crank lengths for track, road, or MTB.

As did I. I am almost disappointed.

That's interesting to hear. I would think shorter crank on the hills makes it easier to turn the gears vs. Longer crank.

My crank lengths vary from 167.5 on the fixed gear to 180 on the bmx race bikes, with in-between lengths on road and mountain bikes. Personally, I can feel the difference, but after a few cranks, my legs seem to switch into to the right mode, and no problems.

Not to knock on an established rider like bob, but do you have a good sense of how long 5mm really is?

It's about | | <-- that long. Over the length of your entire leg, were talking about a single digit percentage of difference.

That said, I can feel the difference between my bikes with shorter and longer cranksets.

I have 170 on my SS and 175's on my road bikes.

I honestly can't tell the difference.

There has been a trend over that period of time to put longer cranks on the same "size" bikes, but it has usually been limited to a 2.5 mm difference. I suppose 5 mm longer on the same size frame isn't outside of the general range of the trend. One explanation is that 170 mm cranks on road bikes, esp. lower end ones, may have been standard at one time no matter the bike size. Now it is much more common to have cranks sized proportionally to the frame size. From the mid-level to upper end of frame sizes, that could make for discrepancies like the one you have observed.

Correct.

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