[A4] tires, speaking of tires, anyone have any used 17's lay'n around?

[Sean Reifschneider]

On Thu, Dec 27, 2007 at 01:14:33PM -0500, Huw Powell wrote:
> Yes, but forcing a differential to constantly rotate to make up for tire 
> diamter issues is hard on it.

It's a matter of degree.  As I said, you will almost never have exactly
identical rolling radius on the different tires.  The difference between a
brand new tread and one that's at the wear bars is around 7mm on these
types of cars.  That's just over a quarter of an inch.  Brand new tires
inflated to exactly the same pressure will be close.  But, the fronts wear
faster than the backs.  Oh, and don't ever park your car so that one side
of it is in the sun, that'll cause the pressure on that side to be much
larger than on the shaded size.

How far do you really want to take it?

Yeah, it's your car, you can worry about these things all you want.  Me,
personally, I'll go with Audi's recommendation, and that replacing a flat
tire for a nearly identical new one is fine.  I wouldn't put a different
size on different wheels, but a new versus a used tire is almost certainly
fine.  It sure was in my experience.

> To take care of your diffs, they should at least be the same size.

Absolutely, if we're talking about putting a 55 series tire on a car with
60s on the other 3 corners, I totally agree that that's stupid.  But if
we're talking about putting a new 55 on a car with 3 others with 25k miles
on them, I would do it without worry.

Sean
-- 
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Sean Reifschneider, Member of Technical Staff <jafo at tummy.com>
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