Just noticed something I find a little odd, my car has done 17,000 miles, the rear tyres are just about on the wear bars, yet the fronts still have a little (1.5mm) of life left in them, now I always believed the quattro/haldex system mainly drove the front wheels, only supplying torque to the rear when required, so being as the front appears to have more work to do with weight, acceleration, steering and braking why are my rears worn more than my fronts?
Quattro Tyre Wear.
- Thread starter johnmv55
- Start date
Remember with quattro you have to change the four tires at the same time, otherwise the differential might seizure... so I was told... Double check this information with your Audi dealer...
Pedro
Pedro
i also find it strange why the rear brakes always wear faster than the fronts as its supposed to be the fronts that do most of the braking - this has manifested itself on my last A3 by the back wheels getting dirtier faster than the fronts and its normally the other way around.
newbiecrg said:
I owned an Impreza WRX with permanent 4wd and had to change 1 tyre due to a puncture.
I was dreading that I would have to change all 4 at once, but 2 seperate tyre fitting centres told me that the difference in the circumference of a new and old car tyre was so small that it would make no difference to the diffs.
I guess it could be a different story with a off road 4x4 vehicle with heavily treaded tyres.
I would always balance an axle at a minimum because using a part worn tyre / new tyre will mean inbalance in grip / braking, in addition it will also generate more heat in the diff. With a 4wd car you will also generate more heat in the centre diff as well, it may be within the operating limits of the diff, then again it might not. I would follow audis recomendations on this, not a tyre fitter that prob jacked the car in the wrong place.coupe-se said:
Chris.
Well who told me this was a Audi dealer in Portugal that had a lot of A4 quattros with seizure diffs some thousand miles after the owners did not change the 4 wheels at the same time... I have to read my S3 intruction manual regarding this issue...
Just Audi guidelines...
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Pedro
Just Audi guidelines...
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Pedro
I personaly would, and always do swap tyres as a pair on each axle.
The tyre fitters I know are independant companies, extremely good and know their stuff. If you think about it they have a vested interest in selling 4 tyres rather than 2 to extract more cash out of your pocket but proffesional tyre fitting centres do not need to stoop to such lows.
Bear in mind that the natural differences in wear front to back means that; apart from when all tyres are brand new; the fronts and rears will always have different amounts of tread and different circumferences. The difference is minute that it will make no difference. We need a maths bod to work out the actual differences in rotational distance for a given amount of tyre wear.
The tyre fitters I know are independant companies, extremely good and know their stuff. If you think about it they have a vested interest in selling 4 tyres rather than 2 to extract more cash out of your pocket but proffesional tyre fitting centres do not need to stoop to such lows.
Bear in mind that the natural differences in wear front to back means that; apart from when all tyres are brand new; the fronts and rears will always have different amounts of tread and different circumferences. The difference is minute that it will make no difference. We need a maths bod to work out the actual differences in rotational distance for a given amount of tyre wear.
I always change tyres on an axle basis
if you have a brand new tyre and a tyre at 4mm, it will be a large difference in total outside diameter
meaning if one wheel does 10 complete turns to cover 50 meters, the other wheel may turn 11 times, putting stress on the diff
if you have a brand new tyre and a tyre at 4mm, it will be a large difference in total outside diameter
meaning if one wheel does 10 complete turns to cover 50 meters, the other wheel may turn 11 times, putting stress on the diff
The A4 has a Torsen diff system, where different rolling radius of the tyres is an issue, but the A3 uses the Haldex system, where no such issues exist.
I would always have the same tread depth on each axle though, from a safety point of view, but if you don't it won't damage anything.
There's lots of information on this on the Haldex website.
EDIT: claudefrog, the scenario you describe is a 10% difference in rolling radius, and such a difference would cause you far more problems than the diff wearing!! I see your point though, but don't forget that diffs are on our cars to do what exactly? I always thought they were to cope with the difference in rotational speeds at the wheels on each side of an axle.... So, they'd be doing their job, and the rolling radius difference would be so tiny on a few mm of tread, that it won't cause any problems.
I would always have the same tread depth on each axle though, from a safety point of view, but if you don't it won't damage anything.
There's lots of information on this on the Haldex website.
EDIT: claudefrog, the scenario you describe is a 10% difference in rolling radius, and such a difference would cause you far more problems than the diff wearing!! I see your point though, but don't forget that diffs are on our cars to do what exactly? I always thought they were to cope with the difference in rotational speeds at the wheels on each side of an axle.... So, they'd be doing their job, and the rolling radius difference would be so tiny on a few mm of tread, that it won't cause any problems.
OK that's probably why the problems where on the A4, also the same problem on the new TT he told me so I presume that the quattro on the 3.2 V6 is also a Torsen?
Pedro
Pedro
The problem with the diff is the heat it generates. Yes their job is to deal with the rolling radius difference but this is during cornering not when driving straight, so if a radius difference exists the diff never gets a chance to cool. My LSD on my caterham got hot enough to need a oil breather, too hot and the oil would degrade.
Chris
PS the new TT has a Haldex
Chris
PS the new TT has a Haldex
So anyone has a A3 quattro manual to clarify this? My S3 only arrives mid March...
So shall we change the 4 tires at once or not?
Pedro
So shall we change the 4 tires at once or not?
Pedro
newbiecrg said:
No just tyres on the same axle. The haldex clutch pack is constantly moving power about and is designed to take into account front and rear rolling radius differences. The even talk about it on there site that with the same size tyres the rolling radius will be different anyway due to the weight over the front wheels.
Im pretty sure you will only get real problems with odd tyres on cars fitted with LSDs. After all most cars out there will at some time have had a new tyre fitted on its own to the driving axle and how many failures are there.
This may help!
Taken from http://www.haldex-traction.com/default.htm
Technical information page under Control Samples.
Different tyre wear and pressure conditions
An algorithm in the ECU detects differences in the diameters of the tyres and compensates the characteristics accordingly.
This means that is does not matter if you only change a single tyre. This is demonstrated when using the daft spare, your diff does not explode!
Also for those whos A3 Quattro is coming up for the MOT tell your test station that when brake testing the coupling is not activated until a preset engine speed is exceeded. This means that the coupling is not activated, even if the ignition is on. That means that the car can be tested on the standard two wheel test rig. Note they may need convincing mine did!
Taken from http://www.haldex-traction.com/default.htm
Technical information page under Control Samples.
Different tyre wear and pressure conditions
An algorithm in the ECU detects differences in the diameters of the tyres and compensates the characteristics accordingly.
This means that is does not matter if you only change a single tyre. This is demonstrated when using the daft spare, your diff does not explode!
Also for those whos A3 Quattro is coming up for the MOT tell your test station that when brake testing the coupling is not activated until a preset engine speed is exceeded. This means that the coupling is not activated, even if the ignition is on. That means that the car can be tested on the standard two wheel test rig. Note they may need convincing mine did!
Thanks for that, I used to do an awfull lot of 911 work, we had a 911 turbo2 in that was f******g dangerous, it would change lanes on the by-pass with on or off throttle application QUICKER tham would be possible with steering input, turned out the customer had put one new rear tyre on the car of the same make but apparantly Bridgestone had changed the construction, the tyre circumference was 1" more on the new tyre, which is not much on basically a 6 foot (ish) circumference, but it means one rear tyre has to travel 12 " further in 12 revolutions which is enough with a LSD to make it very scary!!
By the way, are the preffered tyres still GD3 F1's?
By the way, are the preffered tyres still GD3 F1's?
Back to the original topic
I have noticed this anomaly regarding rear tyre wear as well. I owned 2 8L models of the S3 prior to my current 8P model and in both cases the rear tyres wore down abot 1-2mm faster than the fronts.
I have heard all the discussions about the Haldex system being essentially front drive unless called upon to divert power to the rear, however given the evidence of the rear tyre wear, particularly if you consider the additional wera on the fronts imposed by steering loads, there would appear to be other factors at work here.
I have a collegue with a Passat 4 motion, again Haldex, who suffers from the same rear tyre wear.
So I am not surprised you are suffering from this, it appears to be common amongst Haldex equipped cars and I full expect my 8P S3 to have the same issue
I have noticed this anomaly regarding rear tyre wear as well. I owned 2 8L models of the S3 prior to my current 8P model and in both cases the rear tyres wore down abot 1-2mm faster than the fronts.
I have heard all the discussions about the Haldex system being essentially front drive unless called upon to divert power to the rear, however given the evidence of the rear tyre wear, particularly if you consider the additional wera on the fronts imposed by steering loads, there would appear to be other factors at work here.
I have a collegue with a Passat 4 motion, again Haldex, who suffers from the same rear tyre wear.
So I am not surprised you are suffering from this, it appears to be common amongst Haldex equipped cars and I full expect my 8P S3 to have the same issue
