# Carbon wheels

I have a simple question for you but a difficult one for me.
My bicycle rim manufacturer tells me that the carbon bicycle rim brakes at 900 pounds
of pressure.

If we have a cyclist of 300 pounds riding at 30 mph and he hits a pot hole for example.
What is the amount of pressure/force he will build up on that impact ?

If that is more than 900 pounds i would think the rim will break ?

I know it is difficult because you have tires around it that absorbed the shock in real life.

Maybe you could help me out with some kind of calculation that gives me an idea ?

Thank you
Roel Vanmuysen
BelgiumBike.LLC

russ_watters
Mentor
Welcome to PF.

Pounds is not a unit of pressure. Do you mean force or do you mean pounds per square inch? You're talking about the wheel rim, right?

Welcome!

I'm pretty sure that the reference is to pounds, as 900 psi is much higher than tire pressure, even during a pothole collision. In addition, a static test is much easier to do than some sort of dynamic test of the sort that would measure resistance to potholes.

I think your best bet is to find a 300 pound cyclist, get her up to 30 mph, and see what happens when she hits the pothole of your choice. Results will be much different depending upon pothole dimensions, wheel size, etc, etc. Her hospital bill will probably be much cheaper than the cost of a finite element analysis of her, the bike, and the pothole.