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Am looking to switch cranksets on my jamis nova(steel). Currently have a 105 with 53/39 rings. The LBS has two FSA gossamers. One is a 175mm with 46/36 slightly used. The other a new 172.5mm with 50/34.
First race in November, thinking the 46/36 but how big a deal is the arm length?

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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.
thought so...
Its a 54cm non compact.
6' and 140lbs
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.
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.
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!
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.
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.
Thanks for the direction. Its the 175 with 46/36 change up.
I run 'em short. 170's.
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!


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