AUDI A4 | B5 | 8D 1996 - 2001 FAQ Frequently Asked Questions and Common Problems Thread Collection

[EricBss7_CT]

[TwentyValveB5+S4]

• by andy @ south bend

[TristanP]

AudiWorld is now hosting the pics - instructions on how to add them to your sig are here.

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[RS41AB]

[RS41AB]

[RS41AB]

[list][*]http://www.awe-tuning.com/pages/shar...=1&PEI=2&PP=a4

[andysprague]

[A4SilverT]

What if you blow a single tire? Or wear out the two front tires due to a bad alignment? How many tires should you replace? This has been a contentious issue for a long time on AW, and there seems to be no definitive answer. VAG has caused some of the confusion by their vague statements in the owner's manuals.

First, here's what everyone agrees on. You should install the same size, brand, and model for all four tires so you have the same tread pattern. Doing anything else will affect how the vehicle handles. Don't mix winter and summer tires; if you're going to use winters, use them on all four wheels.

Second, Audi says in their owner's manuals that if you replace two tires, put the new tires on the front wheels. Recent research by Michelin suggests that this is wrong, even when the manufacturer says it. Michelin says (and Tire Rack confirms) that in wet conditions that could cause hydroplaning, having the greater tread depth of the new tires in the rear makes recovery from hydroplaning easier. Detail on this research is available on Michelin's web site and on Tire Rack's site in the tire tech section.

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).

The good news is that most tire failures aren't so catastrophic that it isn't a simple matter of plugging a hole. And if someone slashes all four of your tires, your insurance will take care of your new set, less deductible.

So what this comes down to is whether you can still buy a tire of the same size, brand, and model as your existing tires. Tire manufacturers will generally keep making a tire model for 4-6 years. If you can get the same model tire, then have that new tire shaved to match the existing ones. If you can't buy the same tire, then you're stuck with replacing all four regardless of tread depth unless you can use your spare.

A final thought about replacing one or two tires is that it only makes sense if the existing tires are reasonably new. A brand new tire usually has a tread depth of 10/32". At 2/32" tread depth, a tire is no longer serviceable. Depending on the model of tire, you're going to start seeing performance degredation at 4/32", especially in wet situations. So if your existing tires are 5/32" or less you're going to need a whole new set soon anyway. Might as well bite the bullet and just get four new ones.

[JA4T]

• Autotech

[S4iowa]

UPDATE: 10/4/2008
Adjustable options are

Stern (from PureMS)

BHR
BHR

CPT
CPT

K-Mac upper control arm bushing replacement kit.

CPP is out of business, but would still be available used
CPP adjustable replacement control arms.