Beyond Round and Black. More than you want to know about tire grip

[Traction]

Stumbled across this great technical article on tire grip, and I was surprised at how much I didn't know about how much science and testing that goes into tire design. There is definitely more to a tire than what they look like, or cost. I'm guessing some of the cheap line tires probably skip a few steps.

https://www.paradigmshiftracing.com/uploads/4/8/2/6/48261497/tyre-grip-michelin.pdf

 

[CR94]

Thanks! That's an impressively detailed introduction to the traction side of tire engineering, yet generally avoids math beyond basic algebra. Tires are very complicated.

 

[CapriRacer]

Thanks for that.

A couple of interesting tidbits:

1) On page 25, they talk about inflation pressure and contact patch pressure - and while they don't actually come out and say it, the data suggests that you can't determine the size of the foot[print knowing the inflation pressure and the load. There are other studies that confirm this - mostly indirectly.

2) On page 30, they talk about dry vs wet grip - and indicate that some surfaces which have very high dry grip can have very low wet grip. There are other studies that verify that wet grip can be extremely low - on the order of ice.

3) On page 61, they show that a car tire can hydroplane as low as 30 mph (underinflated) and at as low as 42 mph when properly inflated. However, they don't comment on the fact that if you are cornering, a tire can break away at an even lower speed.

But that's just from a quick run through. I'm sure there is more.

 

[CR94]

Originally Posted by CapriRacer
... while they don't actually come out and say it, the data suggests that you can't determine the size of the footprint knowing the inflation pressure and the load. There are other studies that confirm this - mostly indirectly. ...
Yes, their numbers say the average pressure within the footprint is greater than the inflation pressure. Is that primarily because of stiffness of the tire structure adding to the internal pressure?

 

[CapriRacer]

Originally Posted by CR94
Originally Posted by CapriRacer
... while they don't actually come out and say it, the data suggests that you can't determine the size of the footprint knowing the inflation pressure and the load. There are other studies that confirm this - mostly indirectly. ...
Yes, their numbers say the average pressure within the footprint is greater than the inflation pressure. Is that primarily because of stiffness of the tire structure adding to the internal pressure?


I think the whole concept that the footprint size is like a piston in a cylinder is wrongheaded. I think what is going on is the pressure is stiffening the structure, much like the way the stiff sidewall works in a RunFlat tire. It's the geometry that dictates the size of the footprint.

 

[RayCJ]

Originally Posted by Traction
Stumbled across this great technical article on tire grip, and I was surprised at how much I didn't know about how much science and testing that goes into tire design. There is definitely more to a tire than what they look like, or cost. I'm guessing some of the cheap line tires probably skip a few steps.

https://www.paradigmshiftracing.com/uploads/4/8/2/6/48261497/tyre-grip-michelin.pdf



Great information. Much thanks for posting it!

Ray