Hi there,

I was searching for basics about cornering in vehicule dynamics but didn't found anything graphical (illustration). I'd like to know what are the vehicule motions when you turn, that is, what kind of motion do the car achieve when you corner.

Also i'd like to ask what are the implication of the low slip angle vs max sideway force of modern racing tires on vehicule dynamics. With optimum slip angles as low a 3° on a modern F1 car i bet this has some consequences isn't it?

I noticied during GP's that while the lines taken by F1 pilots were not so far for from the classic racing line, they seemed not to be that much on the "accelerate as soon as possible and in straigth line" after the apex. I was wondering if that's a visual artifact or not.


Thank you very much.

It means they don't slow down as much when cormnering.

Okay so that explains the fact that F1 drivers do not end up their turns as straight as in more classic formulas (i often see them straighten the steering wheel only when they hit the kerb).

Is it a property of only modern slicks or is it also present in for example barber like formula's tyres?

A tyre generates a drag force, basically tyre force x sin(slip angle). Lower slip angle gives lower drag. Power to overcome drag is force x velocity, at high speeds the power can be very large. (this must be very important on ovals). There are downsides though, if peak grip slip angle is low the tyre is very "peaky", hard for the driver to keep the grip he wants as a small slip angle change gives a large grip change. The other thing to bear in mind is that the drag heats the tyre (one reason why crossplies are still popular in hillclimbing).
As far as exit line goes, it is conventional to represent the tyre's total grip as a "friction circle" ie the maximum grip distributed between cornering and traction follows Pythagoras theorem. As the car's path radius increases, lateral acceleration drops and can be replaced by pressing the accelerator to increase speed, the object being to follow the "friction circle" boundary. A F1 tyre "friction circle" may be far from a circle.

So you mean possibly for some lateral forces on an F1 "circle" you may have more longitudinal grip aviable (relatively to the lateral grip) compared to some other cars?

That is possible. I have been led to believe that when F1 wasn't a single tyre formula one manufacturer's "friction circle" could be "squarer". I suspect that the shape could be something a tyre manufacturer could change to suit car and track characteristics. Not something I know enough about unfortunately!

Have you got any evidence for that? Reason I ask is the huge difficulty getting tire force data at realistic operating conditions, especially combined slip, especially at racing speeds, and of course the general reluctance of the tire manufacturers to release any data about the performance of their tires (with a few honourable exceptions).

Greg, I personally have no direct evidence. I was at one of Claude Roelle's seminars and that was what he was saying. As you say, any tyre data is very hard to get never mind realistic and combined! Avon used to have some stuff on their website, don't know if it is still available but didn't include combined.
I suspect tyre manufacturers don't actually have any data for the majority of their motorsport products.

I would think it a "given" that tyres from different manufacturers would vary (if only subtly) in many respects including "circularity" of the traction circle.

A drag racing slick for example, surely that wouldn't be a circle (or roughly circular)? Would the manufacturer care for lateral performance at all?