Question about Crank arm length

[girlbiker]

What is the impact on a road bike from changing the crank arm length to a longer length?

does the frame size determine the crank arm length?

specifically going from a 170 to 175

thanks for any info

[nembabill]

Use this formula to determine your best crankarm length.

Crank length (mm) = Inseam (mm) X 0.216

Running a longer crank normally makes powering up hills easier. Some people claim that a longer crank slows your cadence, but I never experienced that.

[C.P.]

What is the impact on a road bike from changing the crank arm length to a longer length?

does the frame size determine the crank arm length?

specifically going from a 170 to 175

thanks for any info


Good advice from bill, I have 181mm cranks on my singlespeed road bike, and I like them so much that when I purchase my next geared road bike, it's going to be spec'd with at least 180 cranks. BTW I'm a 33/34 inseam. For a reference I typically ride a 60.5cm road bike w a 58.9cm top tube.

The only impacts that a larger crankset may have are the possiblility that it might be more difficult to get a good spin (high cadence if that's your cup of tea). For me, longer crank arms caused my spin or higher cadence to slow down a bit, but also allowed me to take advantage of my longer legs and larger quads, in all making smooth "round" pedaling feel more natural and comfortable.

Something that's pretty rare is on some road bikes, esp smaller road frames or race frames with tight geometry, longer crank arms might cause overlap on the front wheel. (Your toe hitting the front wheel when turning and pedaling)

[girlbiker]

Thanks for the helpful info :)