mixing tires with quattro

[4ringAR]

i dont quite understand all the drama behind not running mixed tires on quattro. the spare is not the same size, dont you think they would have included a same-size spare if it was really that big of a deal? unevenly worn/inflated tires surely make more of a difference than mixing tire brands, right?

i bring this up because i want to run my 20's again since its starting to warm up, but the front tires are done for so i would have to get new tires for them. i believe they wore out quickly because of the increased camber with the 402 mod, however i have considered the possibility that running staggered widths somehow caused the uneven wear.

anyways, i dont want to spend close to 300 for 2 tires if they are going to wear out in another 13k(i got a stupid good deal when i bought the tires originally i cant get again), instead i would rather spend less on "cheaper" tires and be less upset if they wear out quickly.

so what do you guys think? am i asking for trouble running different tires on each axle(same size tires, but different brands, and on a staggered wheel setup)?

[Stubek]

different tread patterns and different tire diameters will rotate at slightly different speeds. causing wear on the gears. I think as long as you have the same tires at the front on both sides and the same at the rear, you might be ok. My friend has a subaru with staggered tires and just replaced the fronts only.

[seanj130]

I have always ran 2 different sets of tires. For 70K I Have been doing it and my car runs very well. Some people on here just look way to far into things, and over analyze everything (which is ok) and give opinions based on no actual experience (Not ok).

[JazzyA6]

your probably thinking different WIDTH not diameter, the spare tire is less wider but that doesn't matter since its meant for a short time use.

[4ringAR]

your probably thinking different WIDTH not diameter, the spare tire is less wider but that doesn't matter since its meant for a short time use.

the allroad's spare is actually not quite fullsize. the tire diamter is over 3% smaller than the stock tire size.

stubek ** i dont understand how different tread patterns would cause a difference any more significant than having tires that are more worn in the front or unevenly inflated tires. im sure the engineers would have built in factors of safety large enough to cover this.

[Stubek]

tread pattern effects rolling resistance. Is it more significant than unevenly inflated tires, probably not.

[Alipor]

I think your ok as long as both tires on each axel are the same, you can run staggered in the rear and something different on the front. So you can run different front tires than rears with out a problem as long as the fronts match, and the rears match.

[Kristopher]

Audi specifies tires with a tread depth of less than 4/32 (.125") (3.175mm) variance maximum. (That's a 8/32" difference in height)

I had to get new front tires and use a good set of Pirelli allroads for the back. The Pirelli is .1" less in radius and has 5/32 (.15625) of tread left. When calculating the total difference in radius it works out to .25625 less for the Pirellis. That's 8/32" vs the 4/32" specified.

To make things a bit less sketchy I've aired up the rears slightly to help bring them a little more height.

I think if you do the maths to see where you're at and keep it reasonable you should be ok. The 4/32" specification is likely quite a conservative estimate.

[redneck truck]

You can't calculate tire heights. My Eagle F1s spec'd out at 25" tall and were just over 23".

The differentials have nothing to do with rolling resistance; it's a simple comparison of speeds.

If two tires on an axle are turning at different speeds, like if you're rounding a curve, the differential is turning. It's not necessarily wearing, but it's turning. I suppose if it turned fast enough for long enough, it would generate some heat and/or wear, but it's there for a reason. I'd be interested to see over a car's lifetime what percentage of miles is driven with the steering angle directly ahead. Does someone want to integrate that and calculate the number of turns any given differential has made, even with the same sized tires?

As for different sized tires front to rear, I don't know what driving condition would generate this besides tirespin. Assuming the same *average* diameter tires on front and rear axle, the center diff shouldn't have to work. The only way I could see the axles traveling at different average speeds would be while towing on a tow dolly, which is not recommended. However, maybe a slight turn here and there isn't harmful.

[Kristopher]

A hard day at the track will heat up the diffs much more than treadwear variance limits on the car.
And there's no way Audi would be allowed to sell a car if an owner used new tires on the back at 10/32" and bald ones in the front if the diff had any chance of damage or locking up. A VC in other awd systems may get warm but it wouldn't fail.