Four new tires because one is bad? Is this really important?

[Cousinphil]

I just flunked inspection because my left rear tire is wearing on the inside corner because of negative camber. I was told by the garage that because it is an all wheel drive car, I must replace all the tires. The two on the front have lots of tread left. The car has a manual transmission. Is this for real?

[A4Avant512]

Yep. If you don’t replace all four tires you risk putting unnecessary stress on the drivetrain because one tire will have a smaller circumference than the others. That’s why it’s important to rotate your tires at the recommended interval.

https://www.lesschwab.com/article/re...d-vehicle.html

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[BARRY]

you can replace a pair....how much tread is left? a pair would be safer. all 4 would be safest.

[Audibot]

If Tire Rack has the tire, you can order it from them shaved down. They will shave it to the appropriate diameter so that it will not affect the AWD system of the car.

[Fourplay]

You can replace in pairs or simply have a shop shave the new rear tire down to match (Tirerack.com does this for a small fee). Not a big deal and certainly wouldn't go out and buy 4 new tires.

[PK Auto Design]

If you replace in pairs make sure you have the same brand and model tires. AWD systems are very particular. Different tires have different wear ratings, you NEED to have the same all the way around.

I would still recommend replacing all four because more worn tire vs a new tire will still wear and grip differently.

[BARRY]

whoa...didn't know tire rack shaved down non-race tires. good to know.

[walky_talky20]

Your car can't tell if the tires are all "new" or not. But it can tell "turns per mile" which is related to the circumference of the tire. That is what matters to your magical quattro (torsen) differential.

Long story short: Audi's official recommendation is that the tires are "the same" circumference. On some models in the past they have further specified it be "within 4/32" of tread depth", which you can mathematically convert to keeping all the tires within 1% circumference of each other or thereabouts. So if the rest of the tires are at least 6/32" tread depth, you can run a new one (10/32) in the mix. No problems. If 2 of them are 6/32" and two of them are new, you're still good.

But if the fronts are at 4/32", you probably should not have 2 new ones one the other axle. Just replace them all, 4/32" is about done anyway. Save them for spares if you wish. The torsen differential does not have clutches, but it does have very high friction worm gears which will create a lot of heat and wear if they are asked to work constantly. Not to mention the all-important magical friction washers. So it will deal with "whatever" for a short time. Even towing 2 wheels down (THE HORROR). But long term, stuff needs to match up.

So the only reason to get Tire Rack to shave a tire for quattro match-up would be if you have 2 tires that are 4 or 5/32". And if that is the case, and you *really* must only buy 2 tires, have them shave the new ones to be 8/32". Not 4/32", that's insane. 8/32" will stay within the 4/32" recommendation and will avoid flushing gratuitous amounts of cash on pre-worn-out tires.

[BARRY]

well.... if your good tires have 50% left, and you replace 1 with a new tire...at some point when your other tires wear down they'll react differently and your car will pull to one side.

some tires, their tread pattern changes as they wear down. if your tires have something like 80% tread left, then you're probably ok with just replacing the 1 tire.

[Cousinphil]

Your car can't tell if the tires are all "new" or not. But it can tell "turns per mile" which is related to the circumference of the tire. That is what matters to your magical quattro (torsen) differential.

Long story short: Audi's official recommendation is that the tires are "the same" circumference. On some models in the past they have further specified it be "within 4/32" of tread depth", which you can mathematically convert to keeping all the tires within 1% circumference of each other or thereabouts. So if the rest of the tires are at least 6/32" tread depth, you can run a new one (10/32) in the mix. No problems. If 2 of them are 6/32" and two of them are new, you're still good.

But if the fronts are at 4/32", you probably should not have 2 new ones one the other axle. Just replace them all, 4/32" is about done anyway. Save them for spares if you wish. The torsen differential does not have clutches, but it does have very high friction worm gears which will create a lot of heat and wear if they are asked to work constantly. Not to mention the all-important magical friction washers. So it will deal with "whatever" for a short time. Even towing 2 wheels down (THE HORROR). But long term, stuff needs to match up.

So the only reason to get Tire Rack to shave a tire for quattro match-up would be if you have 2 tires that are 4 or 5/32". And if that is the case, and you *really* must only buy 2 tires, have them shave the new ones to be 8/32". Not 4/32", that's insane. 8/32" will stay within the 4/32" recommendation and will avoid flushing gratuitous amounts of cash on pre-worn-out tires.

Thanks for all the info. That's what I was fishing for. Now, for my next question, why does every car I own end up with negative camber on the rear wheels? I have a feeling it has to do with cornering hard...

[old guy]

Thanks for all the info. That's what I was fishing for. Now, for my next question, why does every car I own end up with negative camber on the rear wheels? I have a feeling it has to do with cornering hard...

Rear camber is adjustable.You can do it yourself with a an angle calculator and a framing square: Clicky click® Easy peasy

[Nollywood]

Despite all the hype, I have only ever replaced a defective tyre, without replacing a full set, or the other on the same axle.

Unless the rest are pretty low on tread, like 3mm, I would not replace the rest for the sheer fun of it. A brand new tyre is 7mm tread depth.

And I have never had drivetrain failure of any sort, or pulling to one side as a result of just replacing a single tyre. I’ve been running Quattro models since 1988.

[texasboy21]

Determine the tread depth of the new tire and compare it to the older tires. If it is more than 3-4/32 difference replace all of them.

[IndoReef]

my rear driver side tire always wears the fastest, even after alignments i've given up at this point on it.
Just rotate and rotate some more!

[BARRY]

^ maybe you have a dead bushing? that isn't normal.

[PK Auto Design]

Check your alignment. Rear camber is adjustable.

If you car is lowered at all you will naturally gain more negative camber as well.

[Cousinphil]

Despite all the hype, I have only ever replaced a defective tyre, without replacing a full set, or the other on the same axle.

Unless the rest are pretty low on tread, like 3mm, I would not replace the rest for the sheer fun of it. A brand new tyre is 7mm tread depth.

And I have never had drivetrain failure of any sort, or pulling to one side as a result of just replacing a single tyre. I’ve been running Quattro models since 1988.

This is encouraging. My front tires have about 6mm of tread. Both rears have about 3mm. I think I'll replace both rears and see if I can get the camber adjusted. And I think I'm going to be much more conscientious about rotating in the future.

[road_tripper]

I had to put my spare on after popping a tire while using my offroad tires. offroad size was 215 60 16, spare 235 45 17, supposedly only a 3% difference in diameter according to the tire calculators.

I noticed the center diff complaining (as in locking up) under hard acceleration on pavement, so I drove home without telling chewie to punch it.

[imnuts]

I had to put my spare on due to a blowout from a piece of metal on the road. My tires had roughly 4/32 on them and the spare was new with 7/32-8/32 of tread. The only time I notice anything was cornering towards the side with the spare on it. The center diff started binding sooner in the turn than it typically would. I just took turns slower until I was able to get new tires since they were approaching the end of their useful life anyway.

Sent from my Pixel 2 XL

[EuroxS4]

Its all about making money!!!Just replace the worn tire with a matching one and your set.I've done this numerous times on my avant.I have 480k miles and I havent had any issues with the quattro yet!!!

[IndoReef]

^ maybe you have a dead bushing? that isn't normal.

everything is fine to my eyes when i've inspected it multiple times with a 4 foot pry bar.
My car is fairly Slammed in the rear so i've always blamed it on that, I will be replacing the rear springs soon as they have bad jounce and bounce . I honestly don't care anymore it has driven me nuts to many times .

[Cousinphil]

OK. Passed inspection this morning by putting the spare on. While I had the tire off I looked at the camber adjustment. Looks pretty easy. If only I had an 18mm socket. All these years working on cars and I've never once needed an 18mm wrench. The framing square says that I've definitely got negative camber. I'm off to get an 18mm 6 point socket.

[BARRY]

everything is fine to my eyes when i've inspected it multiple times with a 4 foot pry bar.
My car is fairly Slammed in the rear so i've always blamed it on that, I will be replacing the rear springs soon as they have bad jounce and bounce . I honestly don't care anymore it has driven me nuts to many times .

this does explain more...if your rear is slammed your toe has VERY limited movement or adjustment hence the uneven wear on your tires.

[IndoReef]

this does explain more...if your rear is slammed your toe has VERY limited movement or adjustment hence the uneven wear on your tires.

only reason it is slammed is the rear springs have sagged so much even at the highest setting.
Only downfall of the Solo werks coilovers