Audi A8 quattro Tyre Change Question - Confused

[IATM8701]

Hi Guys, Need your help, why is it that you need the same tyres on an audi a8 quattro (3.0 tdi 2006). I keep reading this but no proper reason why. I have seen a audi a8 i really like, one owner (age:50) nice example. only 35k on clock. serviced by audi its whole life however:

The front tyres have (Pirelli)6mm each... the rear tyres have 4.5 -5mm(Dunlop) ...

is this a ba thing or are people making a bigger deal about it than it is.

if you could provide any info that would be great.

Cheers

[mrmr96]

IATM8701 said:

The front tyres have (Pirelli)6mm each... the rear tyres have 4.5 -5mm(Dunlop)

That will not matter one jot. Hope that helps.

[stuartmmcfc]

I like to keep the same brand on each axle but not fussed between front and rear

[ukdennis]

I believe the objective is to minimise the difference between rolling diameter of front and rear tyres. One factor is the difference in tyre wear front to rear, but the other factor is tyre make/model. You'd be surprised at the difference in rolling diameter between some brands of new tyres of the same nominal size

[IATM8701]

Thanks for the reply guys

ukdennis: so how does this affect the car. To my understanding that means one axle could be going faster/slower than the other however does it damage any of the quattro system. Does the system have some tolerance for this?

[rb5er]

Its fine. Whatever the make of tyre the fronts will wear quicker on one if those so there will always be a slight difference.

[ukdennis]

As rb5er says, the different wear rate front to back will usually mean a few mm diff in rolling diameter anyway. The Quattro system would have to cater for this. Mine has. Having said all that, I try to minimise the difference by rotating front to back to even out the wear.

[IATM8701]

That's great. Thanks guys. I'll all honesty. If I buy the car I will probably buy a set of two tyres with same mm tread so that they all do match. Rather be safe than sorry but I just wanted to make sure that the damage was not already there by the previous owner having the difference.

Thanks again.

[IATM8701]

That's great. Thanks guys. I'll all honesty. If I buy the car I will probably buy a set of two tyres with same mm tread so that they all do match. Rather be safe than sorry but I just wanted to make sure that the damage was not already there by the previous owner having the difference.

Thanks again.

[mrmr96]

IATM8701 said:

That's great. Thanks guys. I'll all honesty. If I buy the car I will probably buy a set of two tyres with same mm tread so that they all do match. Rather be safe than sorry but I just wanted to make sure that the damage was not already there by the previous owner having the difference.

Thanks again.

For info, the front wheels always turn faster than the rears, except on a dead straight road. Think about the path that your wheels take, most clearly in the snow. The front wheels steer and carve a wider path than the rears, therefore they are travelling further and hence rotating faster. This happens all day every day. Also, the tyres will be different front to rear due to wear. Again, all day every day. Of course the 4WD system would be designed to cope with this. It's one of the functions performed by the centre diff which all 4WD cars will have.

[blueg33]

What I don't understand is why do people on here say its fine, and Audi don't say its fine?

I emailed Audi's Technical Department via customer services directly on this when I bought my car new in 2007. I can't find their reply but it was unequivocal.

[IATM8701]

Hi Blueg33,

That is very interesting! see this is the trouble I have there seems to be two extreme views on this however audi dont really give a 100% straight forward answer as to why.

I have heard of people who have had one tyre punture and due to this have changed all four tyres and kept three spare or sold them off however this seems extreme.

Wish we could have a stright forward answer with a logical reason.

[mrmr96]

blueg33 said:

What I don't understand is why do people on here say its fine, and Audi don't say its fine?

I emailed Audi's Technical Department via customer services directly on this when I bought my car new in 2007. I can't find their reply but it was unequivocal.

Arse covering and selling tyres I would imagine. But mostly arse covering.

[blueg33]

If arse covering was the reason, wouldn't they say the same for 2wd drive cars with mechanical diffs?

It can't be tyre selling, surely most people buy tyres at any place other than a dealer?

With Viscous diffs, the rolling radius and different grip levels is a potential problem, but most Quattro's have mechanical Torsen diffs.

[mrmr96]

blueg33 said:

If arse covering was the reason, wouldn't they say the same for 2wd drive cars with mechanical diffs?

What do you mean?

[blueg33]

mrmr96 said:

What do you mean?

I mean that if they were intent on arse covering, they would stipulate that on 2wd cars you have to have similar rolling radius across the driven axle.

(Maybe they do, its been some time since I owned a 2wd VAG car. They certainly didn't say it in the Cupra handbook)

Maybe I am not cynical enough.

[IATM8701]

Maybe they don't say it because they know people would realize it's utter garbage?

[blueg33]

I just can't see the motivation for them to make it up, at least not with mechanical diffs

[jason s4]

FWIU, the general rule is that if you replace a tyre, they should be done in pairs.

[IATM8701]

Jason what do u mean by they should be done in paris.

Any Audi techies out there that can actually explain if firstly this rule of all four tyres must be the exact same and if so the reason why.

As mentioned earlier in this post even 4 new tyres would wear differently with a different of 1-2 mm different rear/front.

I understand if Audi said it diddnt affect longevity of the vehicle but it greatly affects how the car handles on regards to grip but I genuinely don't believe Audi openly says there car is made with wo much precision that if the tyres are 1-2mm out or front of pirellis and backs have dunlops your car is on the path to dome. They are both similar tyres etc etc have the same effect. Now I'm not saying oooo they are a v v close match but it's not to the point one set are slicks and the other axle have studs.