<center><img src="http://www.tirerack.com/images/tires/yokohama/yo_parada_spec2_ci2_l.jpg"></center><p>Do I really need to have Tirerack shave a portion of the brand new tire or buy 4 new tires? I need to replace one tire, the other 3 have 30-50% tread wear.

From the B5 FAQ:

"But what if you want to put one brand new tire (with a tread depth of 10/32") into a mix of older tires with less tread depth? Here's where the confusion starts. From the 2001 B5 owner's manual (for quattro cars):

"All four wheels must always have the same rolling radius. Different tires on the front and rear wheels may impair vehicle control and will damage the All Wheel Drive because of the constantly different wheel speeds. The proper function of the system is not affected by unevenly worn tires." (page 177)

What does "unevenly worn tires" mean? If it means that the outside tread or inside tread is more worn due to under- or over-inflation, that makes sense. But if the overall tread is more worn, that would change the rolling radius. Each 1/32" of tread wear causes 1/16" change to the diameter of the tire, and the circumference of a tire is its diameter times pi. So wear your tires halfway down (10/32" to 6/32") and you've changed the diameter of the tire by 1/4". You can use tire size calculator to see how much that will affect your speedometer for your setup, but that's roughly a 1% change.

Tire Rack asserts that Audi owners' manuals allow the tires to be "within 4/32-inch of each other in remaining tread depth." Sounds like a good rule, but that's not in the 2001 manual. And Audi mechanics aren't reporting a flood of damaged differentials; in fact, the differentials seem to hold up very well if given minimal care.

So if you blow a tire beyond repair, what are your options other than buying four new tires if you want to keep tread depth within 4/32"?

First, if you had a spare of the same brand and model that you put into your tire rotation pattern, your spare will be close in tread depth. However, if the tire tread is directional, using a five-tire rotation may involve more effort than you want - at some point, you'll have to remount a tire. And you'll need to rotate the tires frequently, no more than 5000 miles between rotations, or whatever it takes so that the variance between tires is no more than 1/8".

Second, you can buy a new tire of the same brand and model from Tire Rack (and possibly elsewhere, but Tire Rack advertises the capability) and have them shave it to match for an extra $25. This assumes that you can measure correctly to give them the proper tread depth and that the tire manufacturer still produces the tire model in question (meaning that they haven't changed the tread pattern while keeping the same name)."

 

I definatley wouldn't risk using tires of different diameter so I ended up replacing all 4 of my tires. If you have a roadside hazard program, insist that they replace all 4 if one is irrepairable and if they are worn more then 4/32".

 

since that is where the steering and the the majority of the braking is being done. The couple of tenths difference is negligible at most. The important thing is that all four tires are the same brand, model, and tread patten, etc., etc., etc.

Heck, having different tire pressures or extra weight in the car can change the rolling diameter.

Don't forget to save the one good tire, if you are replacing two tires. It may come in handy one day.

 

I developed a tire bulge in the sidewall one of the OEM ContiPro Contacts at 21,500 miles. It was in the front tire and the front tires are more worn than the rear. I played with the idea of putting the brand new spare on, buying one new tire and using the other front worn tire as the spare. First off, if you do this...you should put the new tires on the rear axle. Second, I haven't yet, but I'm going to buy 4 new tires because:

1) I'm not happy with the OEMs
2) I feel as though this will put me in a cycle of always replacing only 2 tires.

Not sure how you feel about your current tires, but I think that would weigh heavily in your decision to buy just 1 or 4 new ones.