Smaller crank arms for cross

[Erik_A]

I was about to pull the trigger on new 175mm cranks; But am now considering going w/ smaller cranks 172.5 after reading this: http://sheldonbrown.com/cranks.html

Looking at OEM cross bikes, it seems that the cranks are 2.5mm shorter than road bike equals. Is this for toe clearancein the turns, or for easier spinning up hills.

What is the general consensus?

[benitosan1972]

CX = higher BB for clearance + shorter cranks for spin

[Bruce K]

Toe overlap should be overcome with cx frame geometry not crank length

BK

[Erik_A]

Do the shorter CX cranks feel weird coming from longer on a road bike? I am 6'-4" tall, and until now never considered shorter cranks. CX = higher BB for clearance + shorter cranks for spin

[benitosan1972]

Actually, the raised BB height will bring the cranks closer to you, so shorter CX cranks feel the same (to me). For example, I use 175mm for road & 172.5mm for CX. You should ride a CX frame a size smaller than your road too, to help with dismounts, etc. I ride 58cm road and 56-57cm CX, plus the toptube is lower on CX for dismounting.

[Erik_A]

Actually, the raised BB height will bring the cranks closer to you, so shorter CX cranks feel the same (to me). For example, I use 175mm for road & 172.5mm for CX. You should ride a CX frame a size smaller than your road too, to help with dismounts, etc. I ride 58cm road and 56-57cm CX, plus the toptube is lower on CX for dismounting.

standing over your cross bike with shoes on, how much clearance should you have?

[echelon_john]

unless you plan to stand in that position during a race, that measurement is irrelevant.

standing over your cross bike with shoes on, how much clearance should you have?

[benitosan1972]

standing over your cross bike with shoes on, how much clearance should you have?



Your/my standover is lower, toptube for CX is lower to aid in dismounting/clearance so you don't crush thy nuts on the toptube.
CX bikes should feel a tad smaller for the climbing/spinning/dismounting
done while actually riding them in CX conditions. I think the toptube length
should be more important, CX setups are a bit different than road cuz of the geometry required in the sport... my seattube is much shorter, standover is lower... overall saddle height a touch lower than road but reach & setback are the same... this is for me though, I don't know what's correct, but it feels good to me... to answer the OP question, my cranks are 172.5mm per OEM for my 56.5cm CX (this is the TT measurement c-c).