crank length

kjanracing

I'm running a SRM 53/39.  I'd like to go compact and there is a unit on Ebay that is just the power meter with compact rings.  It has 175mm cranks.  I've always ridden 172.5's except on a tandem several years ago and it had 175's.  My inseam is about 32".  Any opinions on this?  I've read some archives here and ST, but thought I'd ask anyway.  I'm doing IMAZ, so won't really need the compact for that, just looking ahead to IMCdL.    I think if this PM had 172.5's I'd bid on it.  Sooooo, thoughts?

Thanks!

William Jenks

The trend these days is to go to shorter cranks rather than longer. The essential reason is that you can get lower without getting your knees into your chest/elbows. I have the same inseam and 172.5s as you. I would like to experiment with 165s but haven't figured out the cost effective way to do that.

kjanracing

Yeah, I really don't know if I could tell the diff. if I didn't know what lenght they were. Doesn't seem like 2.5mm of radius would make a whole lot of difference. 165's are a different story, I can feel a difference with those. Still thinkin....

Chris G

 2.5 mm actually makes a pretty big difference.  the switch would at a minimum through the fit on your tt bike way off.  I went with 170's on my tri bike and am very happy with them.  I have a 33 inch inseam.  No way would I go with 175's.

Recently I had a chance to ride a bike with one 172.5 and one 170 crank on it.  You could tell something was wrong/different immediately.  It was super obvious. Far more so than I would have ever imagined.  YMMV.

samritter

 With a 'proper' bike fit, you'll know when you're off by a millimeter.  I wanted more of a chance to play with different crank lengths before I ordered my new bike, but I went with the expert opinion of the folks at my local bike shop.  I got the 175mm crank length on the new bike as that's probably what I would have tended towards anyways with my power output and size.(6'4" 250# ~10% body fat, ~320W FTP)