# MotoGP and knee sliders

• B
Hi :)
I have a question or maybe something more like a mind puzzle (at least for me
The drivers of MotoGP touch the ground with their knees while turning. For this purpuse they wear knee sliders made of rubber.
Now I was thinking how it would work if they added a small wheel to the knee sliders. This way there would be less friction and they could lean more.
Or am I wrong? Can somebody explain the physics behind this dragging your knee on the ground?

berkeman
Mentor
Hi :)
I have a question or maybe something more like a mind puzzle (at least for me
The drivers of MotoGP touch the ground with their knees while turning. For this purpuse they wear knee sliders made of rubber.
Now I was thinking how it would work if they added a small wheel to the knee sliders. This way there would be less friction and they could lean more.
Or am I wrong? Can somebody explain the physics behind this dragging your knee on the ground?
Welcome to the PF.

The knee pucks are made of low-friction plastic, so you will not decrease the friction force much below what it is now. Riders mainly use the pucks as "feelers" to help them stabilize their lean angle.

besides that, a wheel has a preferred direction of travel. Suppose the riders knee touched down and the wheel was not pointed exactly parallel to the direction of travel. This could easily throw the rider off balance and cause an accident. An answer to this could be to use casters or spherical rollers, ,but then you'd still have the problem of the wheels jamming on small pebbles. Ever been pushing a shopping cart through a parking lot when one of the wheels suddenly stopped turning because a tiny rock which acted like a wheel chock?

CWatters
Homework Helper
Gold Member
I don't think you want to put weight on the knee (or any wheel mounted on it) if that results in less weight on the driving wheel?

I suspect there might also be something in the rules about motor bikes only having two wheels.

CWatters
Homework Helper
Gold Member
As I understand it they use the knee for two main reasons:

1) to help judge the lean angle and
2) in emergency when the bike starts to slide.

It's not normally used to keep the bike up.

berkeman