Wider Tire = More Grip, right??? Hmm...

[Chernaudi]

Audi and Peugeot, as well as Nick Wirth (designer of the Acura ARX-02, which started the trend I'll address) claim that with more weight biased towards the front of their cars, that wider tires should be fitted, provided that they can/were designed for the job, to offer up more grip.

The Audi R18 and the new Peugeot 908 run the same basic 14.5x18 wheels front and rear, unlike the R15 and the old 908, which ran 13.5x18 front wheels. The R15/908o had 13" wide front tires, and had big diesel engines in the back of them, the former a V10, the latter a V12. The new cars have about 14" wide front tires and the Audi has a V6 and the 908n a V8, and shorter wheelbases than the older cars (the R18's wheelbase of about 114" is much shorter than the R15's massive 121") means more weight up front, so they can use that weight to run a wider tire, as well as the fact that a wider tire means more grip.

Even the Acura ARX-02 proved that, but was hampered by an underpowered, gutless engine (even among gasoline LMP1s), and that, unlike the R18 and the 908n, have front tires designed for the job at hand, instead of using the same exact tires as at the rear.

[Matra et Alpine]

LOTS of downforce completely alters the physics of tyre grip/width/size

Those comments reflect the past of whree rears were larger rubber on equal weights/forces to handle the additional traction needs of power and laterel. Fronts handle steering inputs and not power. By using aero and weight distribution to put more on the fronts then you will want to increase to match.

I assumed on this wider tyres it was on a like for like basis ?
There are variables in design and handling which alter what you want to do on tyres --- eg if you want more oversteer on a FWD then put skinny over inflated tyres on the rear