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need advice: crank arm length(5 posts)

need advice: crank arm lengthMarco
Oct 8, 2001 6:36 AM
I am building up a road bike for the first time, and need advice on what length crank arms to purchase. Is it related to strength, is there a formula, or does it really matter? I have an 82cm inseam. I have 175mm on my mountain bike.
Leg length and riding typeMick
Oct 8, 2001 6:46 AM
As I know it, the convention wisdom is a combination of your leg length and riding type. Longer legs work better with longer crank arms. Longer crank arms are better for climbing hills but harder to spin on flats.

My inseam is 88 cm and I ride in hilly terrain. I use 175mm crank arms and they seem to work very well for me.
Stick w/ the 175's for the road bike...Cima Coppi
Oct 8, 2001 6:47 AM
If you are comfortable with the 175mm arms on your mtb, go with them on your road bike. The only formula that really works for figuring out crank arm length is inseam length and personal preference. I have an 87cm inseam, and I ride 180mm cranks. I do not think you need to go this long, and I also do not really think you can benefit from dropping down to 170's unless you want to be able to spin more.

re: need advice: crank arm lengthcyclequip
Oct 8, 2001 6:50 AM
Most traditional measuring formulae would have you on a 170mm crank with your inseam. If you want more leverage in your pedal stroke cos you ride hills, try a 172.5mm.
Don't overthink this.Ian
Oct 8, 2001 9:09 AM
I also went with 175mm on my road bike becuase that is what I had on my MTB. Then my MTB riding started to fade and I was building up another road bike. I started thinking, "Hmm, I'm 5'11", maybe I should 172.5mm."

Then I saw someone on this board say, "Stack two credit cards on top of each other, that is the difference between 172.5mm and 175mm."

I decided to just stay with 175mm.