Tyre Sizes

[g5und]

Maybe this is a daft question, but I was always under the impression that a quattro set up must have the same tyre sizes all round?

With the RS3 having a slightly larger profile on the front - 35% of 235mm vs. the rears which have 35% of 225mm I was wondering if this is a problem? If you take a close look at the car from the side, the profile difference in the tyres are quite noticable. I'm guessing Audi have configured the quattro system to handle this variation in tyre sizes, but wondered if anyone knew for sure?

 

[Dave Hedgehog]

quattro has come along way over the years, all versions can easily handle different rolling radius on different corners (different tyre wear)

haldex being 90% drive to the front most of the time is even more tolerant of differing rolling radius

 

[jerseypaul]

quattro has come along way over the years, all versions can easily handle different rolling radius on different corners (different tyre wear)

haldex being 90% drive to the front most of the time is even more tolerant of differing rolling radius

You would need to have the same rolling radius on each axle to avoid wind up of the diffs.
the width of the tyre /wheel combo would be less critical.

 

[Dave Hedgehog]

You would need to have the same rolling radius on each axle to avoid wind up of the diffs.
the width of the tyre /wheel combo would be less critical.

i thought the axel diffs where open on all modern quattro systems and they use the brakes to simulate a diff ?

 

[jerseypaul]

i thought the axel diffs where open on all modern quattro systems and they use the brakes to simulate a diff ?

Not all quattro systems.
there are still proper Torsen / central diffs in the A4 A5 etc and S / RS variants.
i now the A3 /TT has longitudinal motor and Haldex set up but I'm surei remember reading in the owners manual re rolling radius requirements.