Driving a CS with one tire slightly "larger" than the other 3

[Ricky1]

Here is the situation:

• [*]Looking to buy a CS[*]Found one[*]All tires look good on the outside with about 7/32" tread left ( Scorpion PZERO 295/30/22, new tread depth = 10/32" )[*]Front side marker light fixture is half full of water with bulb glass parts inside... fine, I can fix that[*]Bought it ( I did look at other things... this is the abbreviated scenario, but admittedly not thorough enough)[*]Took out front tire to get at the side marker light and heard stuff inside the tire as I was rolling it out of the way... not good![*]Took car to tire shop... not all shops can handle 22" wheel...[*]Took tire off wheel and found about a handful full of rubber pieces inside, popcorn size[*]Someone drove it with the tire flat... @#$%&*![*]On the inside of the tire there is a well worn ring tracking the tread-sidewall "joint"[*]The other three tires were OK when they were taken off and rolled... ie. no stuff inside

Question:

When I replace the bad tire with a new one, there will be a 3/32" difference in tread depth, therefore the overall circumference of the tire will be greater. Will this difference in circumference result in a different enough of a "wheel speed" to confuse the CS's electronics (eg. Traction control or whatever else that montors wheel speed)?

AWD vehicles as a rule should have all tires change at once so they all match and tire rotation is essential for even tire wear, right?

There is such a thing as "tire shaving" on a tire lathe... I hope I don't have to go to one. Probably have a tough time finding a place that has one!

So experts out there... do you think the 3/32" difference would be negligible?

Thanks everyone.

ps. My spare tire is an 18" compact inflatable type. If I have a flat, can I use this spare?

Edited April 22, 2013 by Ricky1

[clarksongli]

porsche spec is 30% on the same axle, so you're fine.

[Loren]

porsche spec is 30% on the same axle, so you're fine.

Just to be clear for others - that spec is tread depth - overall diameter.

[Ricky1]

Comfirming that the new tire with 10/32" tread depth is running well with the old tire with 7/32" tread depth. The new tire is on the rear axle.

Page 283 in Manual:

"If one faulty tire is replace it should be noted that the difference in tread depth on one axle must not exceed 30%. Handling inconsistencies may result."

Thanks guys for the advice.