crank lengths

chisa1234 said:

does anyone know the difference that the length of a crank causes.
i am currently using campag chorus 172.5

leverage
a longer lever give you more force by applying the same amount of pressure as before

chisa1234 said:

does anyone know the difference that the length of a crank causes.

i am currently using campag chorus 172.5

Yep, more leverage means you put more torque onto the chainring with the same pedal force, but you have to move your legs through a larger circle...so power output is the same.

From a 172.5mm, a 175 mm arm is only 0.1 inches longer, or 1.5%....not really a huge difference to me.

Your crankarm length should really be chosen based on things like your leg length, and even your thigh-calf ratio. If your cranks are too short, you're not getting optimum leverage, and if they're too long, you're starting your pedal stroke with your leg bent too much at the knee.

Usually when you do a Fit Kit, they take all your measurements and suggest a size. Honestly, if you're off by 2.5mm in either direction, you're not going to screw anything up too bad. But if you're 6'3" with a 38" inseam, you don't belong on 165's. :p

chisa1234 said:

does anyone know the difference that the length of a crank causes.

i am currently using campag chorus 172.5

Honestly, after reading the thread topic, I was just happy to see that this thread was about cycling.

😉

If you make a change of 5mm or more, you've REALLY gotta ease into the new length because there's more knee flexion at the top of the stroke.

I stuffed up my knee by going from 170s to 175s, then hammering for a month; it took a year before my knee was back to normal.

Longer cranks are tricky for criteriums because you're much more likely to hit the ground with your pedal.

chisa1234 said:

does anyone know the difference that the length of a crank causes.

i am currently using campag chorus 172.5

I have found a couple of "measurements" that people suggest.
One is 18% of your leg length, measured from the top of you femure, that part that you can feel on the outside of your hip.
The other one suggests 21 % of the same.

When you know if you are a "masher" ,low cadence, or a spinner, high cadence, then you can perhaps tune your crank length accordingly.
I ride 180 arms, the first 18% measurment suggest 179 mm for me. I am not really a spinner so 180 seemed what to go for.

Claes said:

I have found a couple of "measurements" that people suggest.
One is 18% of your leg length, measured from the top of you femure, that part that you can feel on the outside of your hip.
The other one suggests 21 % of the same.

When you know if you are a "masher" ,low cadence, or a spinner, high cadence, then you can perhaps tune your crank length accordingly.
I ride 180 arms, the first 18% measurment suggest 179 mm for me. I am not really a spinner so 180 seemed what to go for.

180s? You must be a huge grinder! Is this on a road bike or a mountain bike? I'm not sure why it is but it seems that for the majority of people the preference is for 172.5mm on a road bike and 175mm on a mountain bike. I suppose there is a bit less spinning to be done on rough terrain.