Audi Tiptronic

[brickwize]

Hi i was recently informed by a tyre fitter that if i fitted 255/40/18 tyres to the rear axle of my S6 quattro whilst running 255/35/18 tyres on the front the circumference difference could have a detrimental affect on the tiptronic gearbox! Is this guy well informed or just talking nonsense, can anyone shine any light on this matter for me as i dont know what to do now.

 

[antheawad]

I was once told something similar but I was told if any tyres needed changing, then all 4 would need to be done cos it was a 4WD. Didn't mention gearbox, although it's probably what he meant lol.

I mentioned this to someone else and they dismissed this so I'm non the wiser... I don't know who to believe!!!

 

[BahnStormer77]

It's not gearbox specific.... ALL the quattro systems have this requirement: the side effects are slightly different for the Haldex/Torsen system, but for all the Torsen equipped systems (A4's and above) any difference in the wheel speeds will result in in the centre differential having to work harder, which creates heat and wear on the differential, hence why the recommendation is that there should never be more than 4mm difference in the tread depths....

Using the tyre specs of Toyo Proxes T1-R's as a comparison (TOYO SITE), the tyre diameter difference for those two specs will be 0.9", so over 22mm... which is the equivalent of 11mm difference in radius / tread depth!

 

[brickwize]

Thanks for that, looks like the tyre fitter was right with his advise and i wont be fitting the bigger profile to the back axle. Same guy taught me how to age a tyre from the markings on the sidewall, one of the tyres in my garage was 8 and a half years old! Apparently after 5 years you should dump them!

 

[BahnStormer77]

yep - he's right with that too... there's a tyre age guide on the Toyo site too.