Replacing Tire(s) - Ok to replace just one?

[eyoo]

Gotta replace one of my tires. Bought all four together about 15k ago. Discount Tire is recommending I at least replace the rear pair together. Is it really bad to only replace a single tire?

[AccordingToAlex]

It really depends on the treadwear. There's a tolerance that is allowed but I don't know it off hand

[LYKUNO]

From Tire Rack's Tech Page on mixing tires with different tread depth: https://www.tirerack.com/tires/tiret...sp?techid=236..

From page 299 of my 2011 S4 Owners Manual: (Excuse the formatting/typos as this is a copy and paste from an online version of the manual.)
Replacing tires and wheels ...
Tires should be replaced at least in pairs and not individually (for example both front tires or both rear tires together) .
Be sure to read and heed the information to the tire pressure monitoring system * =>page 306.
Always buy replacement radial tires that have the same specifications as the tires approved for your vehicle by Audi. Replacement tires must always have the same load rating specification as the original equipment or approved optional tires listed in the table =>page 291.
Audi-approved specification tires are specially matched to your vehicle and its load limits, and can contribute to the important road-holding, driving characteristics, and safety of the vehicle.

Pretty sure I've seen other documentation concerning the tolerances for tread wear between tires/axles with the Quattro system but too late to find that at the moment.

[Smac770]

If you have the sport diff, you really do want the two rear tires to be the same depth. Put two of your current ones on the rear and then just replace one of the fronts. If you have the open diff on the rear, then replace whichever one.

The spec is the average front tread depth and the average rear tread depth to not differ by more than 2mm. The front and rear (non-sport) diffs are open diffs. They'll handle slightly different rolling diameters inherently. The Torsen center diff is a passive self-locking diff. Substantially different front and rear drive shaft speeds would keep it in a locked state more than desired. I don't understand how that applies to quattro ultra, but Audi continues to quote the 2mm limit for quattro ultra also.

Better just the one than two. One old and one new on the axle will average out to a lesser difference vs the other axle than if one axle was two old and the other two new.

[eyoo]

Thanks guys - really appreciate the help.

[Audibot]

Tire Rack will shave a tire to the right tread depth; idk if Discount Tire will

[Numbahz]

I had this issue last year and the worst part was the tire that needed to be replaced was under road hazard warranty but both my personal mechanic and dealer said since the wear is off a little it's important to replace but more importantly it was a 2022 version of the previous 2019 version which had the absolute slightest difference in tread pattern. I just kept the extra tire to swap around when I need a new one of two. If you feel you should.. now would prob be the best time so you do not have to look back.

[oldzmann]

Tire Rack will shave a tire to the right tread depth; idk if Discount Tire will

If you know a tire shop that has a tire trueing machine, that can shave the tire down to the desired depth.