One Flat Turns to Four

[Louis-Alain Richard]

I'm with you, Steve. 

The tire diameter problem is vastly overrated. It "could" cause problems on a clutch-type very stiff limited-slip diff if the
different tires were on the same axle, and if the difference was substantial. Heck, I've seen donut-spare on vehicles with a limited
slip diff... so it mustn't be that bad. 

Also, on a proper quattro, I can't see any reason to not put a single bigger tire on any axle: remember, open diff there so nothing
can go wrong. Diff would do is job of speed differentiation, and that's it. If you have a Torsen rear, that may be different. But
then, put the bigger tire in front.

And the center Torsen, one could ask ? Well, this one "sees" (or senses...) only half the diameter difference since it differentiate
axle speeds. And these axle speeds are the mean of each wheel speed.  

Result ? Don't worry about it. The new/worn tire difference is no greater than a slightly deflated tire, which everyone of us had on
our Quattro at least once in the past. 

Louis-Alain


-----Message d'origine-----
De : quattro-bounces at audifans.com [mailto:quattro-bounces at audifans.com] De la part de Steve Mills
Envoyé : 1 mai 2012 08:14
À : Brian Pleet
Cc : quattro at audifans.com
Objet : Re: One Flat Turns to Four

I regularly buy 2 and rotate the leftover to a full size spare without having the new tires shaved, and run the new and old on
separate axles, generally with the new in the front because it takes the bulk of the load. Been doing it for the last 15+ years I've
been daily driving /S cars and never had a problem.

Steve 

On May 1, 2012, at 12:58 AM, Brian Pleet <bpleet at telusplanet.net> wrote:

> I blew a tire on my 95.5 S6 traveling between Calgary and Vancouver 
> last week. I heard a clunk, my aftermarket tire pressure monitoring 
> system started beeping and I watched the pressure drop. Unfortunately, 
> that stretch of the Trans Canada highway is the worst across the 
> country with hanging wire nets to catch the rocks tumbling off the 
> mountain. I chose to drive on, aware of the price of a ruined tire. 
> Five km later I stopped in a safe place and changes the Blizzak winter 
> tire with one the summer wheels I was transporting.
> 
> First I'm told you have to replace tires in pairs, to minimize 
> imbalance side to side. I ordered two replacements. Now I'm told that 
> you have to replace the entire set, one for four because the quattro 
> system would be upset by different tire radius. The blown tire was 
> 7/32 tread depth, the other side was 7/32 and the two remaining are 
> 8/32 left out of a starting depth of 11/32.
> 
> Two or four? Suggestions?
> 
> --
> Brian Pleet