Tyre wear VS aero load

[vyselegend]

I'd like to have a clarification from some of the tyre expert here (Jersey Tom if you're around...), about seemingly contradictory statement I heard about rate of wear in relation to aerodynamic charge loading on them.

During the Spa LMS race Nic Minassian explained (speaking about the Audi) that an aerodynamicly discharged car was wearing it's tyre off faster, especially at Spa.
A statement which reminds what I heard from F1's TV commentator about cars suffering greater tyre wear while following other cars (i.e while losing aerodynamic load).

But on the other hand I remember an interview of Pat Symonds (which I can't find back ATM) where he explained that "the more load is applied to the tyre, the greater friction they endure, and so the worse is their wearing rate".

Are those statement really contradictory, or do they depend mostly of tyre construction/ compound and track nature?

Is it possible to generalise the tendancy of tyre wear in relation to aerodynamic load? At least for a given style of racing (open wheel, Prototypes, GTs or touring cars...)?

[raymondu999]

I think the thing is that here you can't really do an A+B=C on this. For example, when you're slipstreaming or in the dirty air, you get the heat from the exhaust of the car in front. This obviously helps to wear the rubber faster. Next, when you have less downforce, there's more slipping and sliding, which also kills tyres. When you have high downforce though, even though you don't slip and slide as much, the thing is you can brake harder and later, and you can corner faster.

In the cases of higher/lower downforce setups, the downforce doesn't actually directly affect the tyre wear. The higher downforce means you can use them more, as you can corner faster and brake faster. that's what's killing the tyres there

[Skinn3r55]

I think it has to do with the operating range of the tire. If you don't have enough aero load you slide around and that kills the tires. If the weight balance is wrong or the aero balance is wrong the tires (front or rear depending on where the CoG and/or CoP are located) are overworked=too much weight is put on them they overheat and start graining.
At least that's my impression about it.

[vyselegend]

Thanks for the answears.

Honnestly I have to admit I still haven't a clear view on this.

What I get now is that Symonds probably meant that since greater DF allows greater cornering speed, you'll get more stress on the tyres. So wearing them out faster mainly because of greater pace, and not because of the direct load applied on them...

So as I should have know, there's no clear tendency in that regard. Now I even remember reading about the sliding resulting from lack of DF potentially being a good thing to keep the tyres on operating temperature when conditions are colder than ideal.
And also reading the contrary, i.e drivers with cold tyres struggling to heat them up in low DF because sliding doesn't allow for enough cornering speed to load them.

Does that means that sliding wears the tyres off, but stressing it in a way that doesn't create heat?

[autogyro]

I think there is just one ideal balance of forces and temperatures that allows any particular tyre to work at its best, with a designed level of grip to wear.
If the car design and set up cannot get to this condition the tyre will either grip less or wear faster.
Blindingly obvious to those who know.
Then of course the complications begin.

[Skinn3r55]

To go to the engineering limit there is always a bit of slip from the tyre. If its just a small degree of slip you can say that the tyre is griping. As the tyre grips it is deformed on the Z axis (vertical). Because of this deformation throughout the tyre the molecules move relative to each other => internal friction => heat in the tyre.
If you don't have enough load on the tyre (mechanical at relatively low speed, aerodynamic at relatively high speed) it doesn't deform enough, so it doesn't heat up. Because rubber is amorphous it becomes softer as its temperature increases so its friction coefficient increases (gives more grip), but its hardness decreases (wears out faster).
If a tyre slides (contact patch doesn't grip) the load isn't fully transmitted from the chassis through the suspension to the tire to the ground. So the tire doesn't deform so its not heated throughout. The only part that heats (overheats) is the tiny contact patch, not the hole tyre. Because it overheats the contact patch becomes excessively soft (you could say it melts - remember this process takes place only at the contact patch and only tenths of millimeters deep in the rubber) so it rips and curls on the surface wearing out the tires(graining - you can see in slow-motion that this is only visible on the center of the tyre which i believe experiences the harshest conditions).
Hope its clear enough (and i'm sure its incomplete and perhaps mistaken in some parts ).

[vyselegend]

Thanks! It's getting clearer now.

Now I understand why the tire grain and doesn't heat properly if it's scrubbed against the ground.

So, if I understood it well, the point is not that the natural wear (drying of the compound) of the race tyre is worse if there isn't enough load for it to grip, but rather that lack of load prevent it to heat up, and lack of heat lead to disintegration of the compound because it's not viscous enough (the rip off phenomena you described). In some way we could say graining and blistering are "unnatural wear" of a mis-used tyre, am I correct?

It also give sense to Minassian's comment that low DF wears tyres off "especially at Spa". Because of the medium and fast corners (Eau Rouge, Pouhon, Blanchimont), there is more relevance in aerodynamic load, as far as grip is concerned.

I'm now less ignorant than yesterday, thanks guys!