AWD tire size difference? - new vs old tire after blowout

General Discussion
#1

Just curious about how much leeway there is with tread difference for opposing tire size, specifically side to side (rather than front to back).

I caught a a screw leaving my apt complex and I think it was just enough to puncture it and then pop back out shortly later. So When I was on the interstate it went from ~35 PSI to 0 PSI in a matter of a couple of miles. I pulled over as soon as I could grab an exit, went and got my spare & jack so I could take the bad tire to a shop but by that time the tire was shot. Luckily I’d for some reason bought the warranty and it only cost 30 bucks for a new tire.

But my question is my other tires have probably 5k left on them, maybe a little bit more, but I’m wondering the difference in a new vs old tire on the rolling diameter, especially since it’s side to side not front vs rear. Buying a new front right to match the new front left wouldn’t be the end of the world, just wondering what the consensus would be on options.

Thanks

#2

I always hear people reference 3% but I’m not sure…that’s a pretty big difference.

As for tread depth causing problems, the dealers I’ve spoken to cite this as a bit of a myth. Then again, not sure dealers are the best source of information.

for some math fun

brand new 255.35.19 tire = 26.0" tall in theory, and should have about 9/32 of tread depth, yes?
a worn one on its last legs has 4/32 of tread depth.
delta is 5/32 of tread depth top and bottom, so 10/32" overall…so vs. 26" a.k.a. 832/32" we’re looking at
10/832…

1.20% difference

#3

^Hmm, very good info.

Yea when you look at a new tire vs worn one, the tread depth appears to be a huge difference, but you’re looking at it from such a magnified view. It’s not nearly as drastic when you’re thinking about the big picture.

The tire shops are always pushing for the new tires in this situation, which I’ve scoffed at usually, (especially on a midsize SUV etc) but I just didn’t want to cause any problems with the audi for such a small cash investment that would be made a couple months later anyhow.

#4

yeah even if brand new was 11/32 and the old one was completely bald its 2.6%… I think getting a new tire would be fine. Or see if ebay has any pull offs, used tires are priced like used condoms

#5

lol it’s true. If you sell wheels with tires on them, the tires come for free. You’ll get money for the tires on their own…but not much.

#6

Don’t let this get out. ;). …I recently convinced Michelin to warranty a pair of tires (instead of the single faulty one) because the new one was at 9/32 and the other side was going to be at 7/32, “harmful to Audi’s AWD system”. …LOL!

#7

did you sell those PS2 yet?

#8

[quote=“beemercer,post:4,topic:3868”]
Quote of the day right there!

And yea that’s not a half bad idea.

#9

Yes, I have a buyer.

#10

That’s so true. I just sold the winter tires that were on the S4. 9/32 of 10.5/32" tread remaing and I sold them for $375. They were $750 or so new.