Crank arm length

Replies to This Discussion

Permalink Reply by Chris Cleeland on October 18, 2010 at 2:38pm

You don't mention frame size or how tall you are, which is crucial.

Personally, I would go for the shortest cranks you can reasonably tolerate. They make off-camber much easier. I'd also go for 46/36 rather than 50/34.

• ▶ Reply

Permalink Reply by Matt sutter on October 18, 2010 at 2:47pm

Hi
thought so...
Its a 54cm non compact.
6' and 140lbs

• ▶ Reply

Permalink Reply by andrew on October 19, 2010 at 11:08am

54 and 6'? that sounds a bit small if you're normally proportioned. could fit well but wondering if you've done a bike fit? i'm a little shorter and ride a 56 and ride either 172.5 or 175, fwiw.

• ▶ Reply

Permalink Reply by DStudley on October 18, 2010 at 5:03pm

Crank sizing tends to be a function of leg length (which less specifically relates to height). What are the 105 cranks you are replacing? Are you content with their size?

Personally at 5'9" with a 31" inseam riding a 52 I run 172.5, have changed back and forth between 175 and 172.5 with out much of a noticeable difference. For cross the specifc frame and BB height for that bike with have an effect in the areas of toe/front wheel overlap and hitting the pedals on obstacles (not that 2.5mm is that big of a difference).

I am guessing at 6' the 175 would be closer to ideal.

• ▶ Reply

Permalink Reply by Matt sutter on October 18, 2010 at 5:37pm

Yes, i run a 175mm now. Toe clearance works(reason i did not get a compact frame geometry).
Thank you,
think i will do the 175 with new 46/36. Don't know till you go!

• ▶ Reply

Permalink Reply by MM on October 18, 2010 at 5:42pm

I'm 6'1" and run 175mm on my cross bike. Personally, I don't think you'd know/feel the difference of 2.5mm, but the 175mm are already setup for cross...and likely less $ as they're used.

• ▶ Reply

Permalink Reply by Chris Cleeland on October 18, 2010 at 5:49pm

Just as a data point, I'm 5' 10" with a 30" inseam and ride 172.5 on the road. My first cross bike had 175 cranks and I was always digging pedals into off-cambers. One night before a race I noticed that my BB was in really bad shape, so I swapped cranks & BBs out for an old set of ultegra 9sp I had in my parts box--that happened to be 170 (carried the chainrings from the 175s over to the 170s). I didn't notice a difference in leg length or position issues, but I did notice that I could pedal through off-cambers. YMMV.

• ▶ Reply

Permalink Reply by Matt sutter on October 18, 2010 at 6:12pm

Thanks for the direction. Its the 175 with 46/36 change up.
Cheers

• ▶ Reply

Permalink Reply by Booksy on October 20, 2010 at 9:48am

I run 'em short. 170's.

• ▶ Reply

Permalink Reply by Matt sutter on October 20, 2010 at 1:10pm

Got the new 2010 FSA gossamer, 172.5 and put new 46/36 fsa rings on it. Just installed and test riden. Wow, torque just like that!
Thanks all.
Btw, i got a 54cm frame with a longer top tube, being 6' i only have @ 2" inseam clear.
Also a phobia of big bikes due to my first road bike at 15 years old that I rode till I was 30 and never grew into. My dad said it would fit in a couple years!

• ▶ Reply