Racing tyres and that.

I have just been watching the world super bikes and was taken by Norry
Haga's back tyre. Now I know they ride round on soft balloons but my
ole road tyres do much the same (for very limited values of same) sort
of thing as theirs but I can't actually see it happening, whereas with
theirs I can.

I am quite happy with what I understand of the forces and stuff and the
way the tyre deforms as they pile on the power and the contact patch
enlarges to something that wouldn't look out of place on a Ferrari but I
don't understand how it appears to move forward. Is it an optical
illusion?

 

In uk.rec.motorcycles, steve auvache amazed us all with this pearl of
wisdom:

Maybe, probably in the same way as a spoked wheel looks like it's going
backwards on film.

Can't say I've ever noticed it myself.

 

Stickiness of the rubber/ground and the torque of the wheel will tend to
do that. Look at dragster tyres - you can actually see the sidewalls
wrinkle as the same effect takes place.

 

Grimly Curmudgeon wrote

I sort of understand that but I was more surprised by the amount it
appeared to move which why I asked if it was an illusory.

 

Whinging Courier wrote

As they exit a corner and get on the gas you can see the tyre flatten
and the patch lengthen as the tyre deforms, with the added odd bonus of
the contact patch apparently accelerating faster than the bike.

 

I haven't looked at any moto GP recently, so can't comment on whether
it's a viewing artifact or not.