How bad is it to change only one tire on a quattro? A friend of mine says you need to replace all tires if you have all wheel drive. I bought all new tires one year ago so there is some wear too them and now one of them needs to be replaced immediatly. What's your thoughts and opinions?

 

Are you sure the tire can not be repaired?

Depends how bad the wear is, how many miles did you put on your tires? Can you abviously tell thet they are well used? If the wear is small, I would've just replaced one tire.
You can possibly look for a slightly used single tire of the same brand and type, some shops sell them.

 

Provided the overall circumference of the replacement tire is within 5% of the others you should be ok. There is some slack in the drivetrain and the differentials will allow some variation.

Think of it this way - when you go around a corner your inside tire has to rotate less than the outside tire in order to go around the corner, and that doesn't hurt anything because the differentials allow it (they slip). If you had some type of locker both front and rear, cornering would be very uncomfortable and the car should shimmy every time you tried to take a corner. Because the Audi AWD system can apply and remove power from each wheel individually, it stands to reason a limited amount of wheel difference is not going to affect things.

Now if you had 55,000 miles on the three tires and needed a new one....then I would just pop for all four. Not worth risking some drivetrain issues for the price of three tires, especially when you factor in how much life is left on them.

 

I changed my right front tire with the spare (brand new) whenI had a blow out. There will be no problems with you driving on the new tire. The quattro is designed to slip like mentioned above and will do no damage. If your beating the hell out of it on a track, then maybe...other than that, there will be no damage to the system whatsoever.

 

this is very good to know so..i was having a question about this....i have a freind that works at subaru and he said that i have to have all the same tires size and wear....so it does mess up the differential. is this right? or the quattro system detect the different size tire and wear and recalculate for it?

 

Let's be realistic. You run completely different size tires (like a donut spare), then you have problems. You have one new tire and three older worn tires, you're only talking afew 1/16" difference in tread depth. What's the math for that: pi * diameter? On a 33" tire that works out to be about .8" difference. You would have more variation in circumference if you did not pay attention to air pressure.

No one would make a vehicle with that little tolerance to variation in tire size.

 

You can always have TireRack shave your new tire to match the depth of your old tires. Maybe Discount Tire or Tires Plus could do the same thing.

 

If I was you, id get 4 new tires, sell the "old" 3 tires and everyone is a winner. For $400 your going to risk maybe messing up your car or worse yet, put your life or your passangers in danger? Not worth it dude, specially with the speeds we drive, just think about it

 

I believe Audi recommends not to exceed 4/32" tire diameter difference. (Why not just call it 1/8"?)

I just leaned all this yesterday when I discovered a bulge in my right rear tire. My 2012 A7 Prestige has Pirellli P7 Cinturato's in an odd size which most tire dealers must order in. I found my local Audi Dealer has them in stock, and their price was actually in line, so I went down to have the one tire replaced, or so I thought! They measured the tires and explained the issue, which I've now verified on several websites and forums such as this one. Four new Pirelli's! Ouch, Ouch, Ouch and Ouch!

Are the three remaining used tires worth anything? They have about 40% left on them. Or are they planter boxes for my wife?

Steve

 

^^ I agree with this 100% on the quattro's if you don't maintain good tire alignment ( I check mine monthly, myself) And if it's off a little I'll go have it done. But uneven wear on a 4x4 car can EASILY ruin your car. Even if 1 tire has a diameter difference of 1/16 of an inch it can cause unnecessary heat on the differential and can burn it out ALOT quicker.

Just rotate your damn tires every 3-4 thousand miles, it takes 10 minutes to do it yourself. Cross rotate, front drivers side goes to rear passenger side and vice versa. Make sure you torque the lugs while the car is on the ground, My book says for a 02 A6 4.2 (my car) 105 ft/lb of torque.