Can someone clear this up for me. Quattro & tyre related.

[Westy]

I picked up a screw in my rear offside tyre today so I popped on the space saver and headed to quick fit. I thought it would be repairable but apparently it had been run on flat and the inside tyre wall was nackered so I needed a new tyre. I'm running Bridgestone Potenza's and quick fit only had 1 in stock so I told him to leave it as I needed to do both rear wheels due to the quattro.

I headed off to Stapletons for a 2nd opinion and they showed me the inside of the tyre wall to prove it was no good, also the rip in the tyre from where quick fit had ripped it off the rim. This meant that even if it was repairable it would have been shagged!

Anyway I wangled 2 potenza's for £220 which is ok. The guy said to me that really I should be getting 4 tyres because of the quattro system doesn't like a bigger difference of 2mm between the front and rear tyres, is this true? My fronts were at 5mm so he said I'd probably be ok. The guy also mentioned that the quattro system was 40/60% ratio front/rear!!!

Now I thought that these cars were prodominantly front wheel drive and the rears were hardly working until needed. This guy was convinced that the rears are doing more work than the fronts. Can anyone confirm?

 

[FazS3]

Quite sure but not 100% but as long as the wheels on the same axle are similar levels of tread on them the quattro system will not have any problems!

 

[jojo]

You will be fine, the Haldex system allows a 5% difference in rotational difference to account for difference in tyre wear I think, so long as the tyre are the same on the same axle, I see no problem.

 

[Olly P]

You need to be a bit careful at these tyre centers! I went to National tires to have some new rear discs adn pads fitted and the guy told me that my tires were illegal and it would be very dangerous to drive home . . .

I had a quick look myself and they seemed prefectly fine. I had my MOT a few days later and it passed with flying colours too!

 

[MartayMcFly]

Quattro doesn't come in to it. Common sense dictates changing tyres per axle, if only to maintain even tyre wear... it's the same reason for keeping the manufacturer and model the same across an axle.

Within reason, a good condition tyre can be left paired with a new tyre, but only if there's a lot of tread on the tyre. But, if there's reasonable wear on the undamaged tyre, it's still a good idea to change it.

p.s. Quattro is a Torsen diff that distributes power evenly to wheels with traction; a Haldex clutch (like the 8L S3 has) moves power to the rear only when the front wheels slip. S3s actually have the 4motion system, technically, but are labelled "quattro" for purely marketing reasons... simillarly, 4motion Passats actually use the quattro Torsen set-up, but are labelled to fit with other VWs.

You're right - "Now I thought that these cars were prodominantly front wheel drive and the rears were hardly working until needed. This guy was convinced that the rears are doing more work than the fronts."

Basically, S3s have a 100/0 F/R power split until the front wheels lose traction. The guy's either lying or an idiot anyway because different quattro equiped cars have different default splits - the R8 isn't set up the same as diesel A4 Avants.

 

[Westy]

Quattro doesn't come in to it. Common sense dictates changing tyres per axle, if only to maintain even tyre wear... it's the same reason for keeping the manufacturer and model the same across an axle.

Within reason, a good condition tyre can be left paired with a new tyre, but only if there's a lot of tread on the tyre. But, if there's reasonable wear on the undamaged tyre, it's still a good idea to change it.

p.s. Quattro is a Torsen diff that distributes power evenly to wheels with traction; a Haldex clutch (like the 8L S3 has) moves power to the rear only when the front wheels slip. S3s actually have the 4motion system, technically, but are labelled "quattro" for purely marketing reasons... simillarly, 4motion Passats actually use the quattro Torsen set-up, but are labelled to fit with other VWs.

You're right - "Now I thought that these cars were prodominantly front wheel drive and the rears were hardly working until needed. This guy was convinced that the rears are doing more work than the fronts."

Basically, S3s have a 100/0 F/R power split until the front wheels lose traction. The guy's either lying or an idiot anyway because different quattro equiped cars have different default splits - the R8 isn't set up the same as diesel A4 Avants.

You're a star mate, I knew I wasn't going mad. I said to him that I'll swap the wheels with the new tyres on from the back to the front as its basically a front wheel drive car, he said I shouldn't! Oh well I ****** well will tomorrow when I take my wheels off to paint my rear callipers.

 

[TheSpaceCowboy]

Generally manufacturers of tyres recommend you fit them to the rear. MartayMcFly is half right, the cars have a different setup dependant on the model, but the S3 according to haldex, is not 100% front wheel unless the wheels slip.

Granted they are set up to change power delivery dependant on rotational difference but Haldex have said typically cars are set up with 15% power going to the rear constantly when cruising (If I remember correctly).