subterFUSE

So we had a rather eventful day in my S6 yesterday. We were driving to St. Augustine to attend a wedding.

We saw a major accident happen 200 yards in front of us on Interstate 4, where some cars wrecked and one of them burned to the ground. The driver escaped the burning car before it lit up, thankfully. After an hour, the police got a lane opened to allow traffic by. We were among the first handful of cars to pass the wreck.

Not 1 mile down the road after passing the accident scene, my flat tire light comes on. I pulled over and found a gas station just in time before the driver front tire went all the way flat.

I changed to the donut spare, and then drove about 2 miles down the road to a Tire Kingdom. I had figured they could just patch my tire quickly and we could be on our way. Not so fast. The tire was damaged on the sidewall right at the rim edge. No repairing that one. So I asked if they had a 255/35/20 tire in stock. Of course not. Only at the warehouse, but it was 5:00 PM on the Saturday before Easter.

I drove to another tire place about 500 yards down the road, same story. No tires in my size. Had to order for Monday. He also made another point which I had not really thought about. He said that putting a new tire on an AWD car with 3 older tires was not advisable because it could cause premature wear to the differential. I felt like I had heard something about that before, so I decided to take this opportunity to ditch my Pirellis for the Michelin PSS I've been wanted all along.

Anyway, my car is parked in the garage at the tire place while they wait for the PSS to arrive. I got a rental car to get to the wedding. We missed the ceremony, but made it for dinner and the rest. And we certainly had an interesting story for everyone.


So my question is about the mismatched tires issue on AWD. Is that for real? Would mounting a new tire with a set of 3 older ones cause any issues?

Second part of the question... If the above is true, then wouldn't driving on the donut be even worse? How far would it be safe to drive that donut?

I think I made the right choice by not driving the car on the donut and just ordering a new set of tires. But I'm definitely curious about this.

diverdan

You can replace a tire a with a few thousand on it to no ill effect. Thanks to potholes, I replaced one at 2K miles (along with a wheel) and another at 10K.
No codes thrown or any other issue. The car now has 20K it, though 5-6K of the recent miles were on winter tires.

nobbyv

I used to think this was all a big myth, but I can't find a source that says you CAN run different aged/brand/size tires on AWD. You'd be fine for a couple hundred miles on the donut. I replaced a blown out (sidewall hole) tire at 5k on my car without replacing the others. Wouldn't push too far past that; 5k was already pushing it.

subterFUSE

8750 miles on my car exactly. I'm getting the 4 Pilot Super Sports. I wanted to ditch the Pirellis anyway. This gave me an excuse for my wife.

stillwaterS6

Tire rack will shave a new tire down for you. To match the remaining three. I think they will only shave some depth, but have a minimum they must leave on the tire that is > 3/32

tenspeed

I think you made the right choice considering the mileage. The new tire would have been turning slightly slower and the differential would be working a little harder.

You might be able to sell your three used tires on Craigs List if you don't mind the hassle. You can also keep one as a spare if you get another flat.

snagitseven

Since Tire Rack recommends replacing a tire at 4/32 if driving on wet roads due to lesser traction and with the legal limit at 2/32, I doubt they would shave a tire that low. Not to mention the shaved new tire wouldn't last very long. If the other three tires only had 3/32 remaining, it would make sense to just replace all four. At 3/32, they are about done anyway.

http://www.tirerack.com/tires/tirete...jsp?techid=157

gatorguy7

Sucks about the cost and all the hassle you went through but atleast you getting some sweet new rubber.

subterFUSE

Yup, it will be like driving a new car once those Michelins are on.

Delurker

+1 agree great choice and you'll love the PSS.