Tyre diameter stagger
 

What exactly does making the rear tyre diameter 2mm or 1.5mm larger than the front diameter affect?

It seems to me that as long as the ride height is correct front and rear, that the difference in diameter has no effect. Is it just that it looks better?

I await the blatantly obvious answer that I should have though of :)

Rear tyres tend to wear quicker than fronts so keeping the rears large to start with balances things out during a race, in a 4wd you Could see improved rotation

assuming your asking on a 2wd pan car...

tire split is pretty useful for tuning steering characteristics.
Larger split - more rear grip, less turn in.
Closer split - more turn in, free rear end.
2 - 3mm of split should be a pretty common number.

its not for tyre wear or cool looks!

Hi Mark

Can you explain why it affects the steering, my brain can't grasp it :) Is it because there's a diff?

Still doesn't explain why, just that it does!

I'll take their word for it and stick to 1.5mm :)

A larger diameter tyre gives more grip, so running the rears larger than the front gives more traction and less steering.

Downside of a larger diameter is that they're more prone to chunking, and potentially less stable.

I agree, but what I'm trying to explain is why the rears should be kept 2mm bigger than the fronts as standard.

I think the reason is contact area which will change according to diameter, but we're talking a miniscule amount. If the same or similar miniscule amount is added or removed from the fronts too, maybe it keeps the balance. And as Mark's document suggests you can tune things a little by varying the balance?

It's the deflection of the tyre that makes the difference. A bigger tyre will deflect more before starting to slide, so more grip.

Running the fronts bigger than the rear will let the front bite while the rear slides, which is hard to drive.