The other week, I slashed two right-side tires on the edge of a manhole. All my tires had 14K miles on them. I asked the dealer to move the old tires on the front and put the new tires on the back, but the adviser told me that on all-wheel-drive cars, they do not do it. Instead, they put the new tires on the right-hand side. The adviser could not explain to me the reason behind this rule. I can only imagine that they think that with slightly smaller diameter tires on the front, the ECU will think that the car is slipping and switch into AWD mode. Am I correct? Is the dealer's argument valid? Thanks!

 

Humm - that sounds pretty strange to me. There has been lots and lots of debate about whether you have to replace tires in pairs (on the same axel) which is often recommended - and some people pushing to say that on 4WD/AWD you have to replace all four at once. In my view there is a lot of confusion on this topic.

Fronts usually wear at a similar rate, and rears at a similar rate, so usually tire shops and dealers recommend replacing in pairs as that's when it's needed (unless as in your case they get damaged). But those pairs are always both front or both rear, I've never heard advice to put the two new tires on the same side. I'd expect that would have some pretty weird driving behaviour.

In my view you asked them correctly - common practice is to put the new pair on the rear of any car (even if it's front wheel drive). Usual rationale is that if you put new tires up front they may well continue to grip, giving you a false sense of security and the back-end with poorer tires will spin out and is much harder to control. So many tire shops insist that new tires go on the rear and won't put them elsewhere.

One issue to be wary of is that if you only replace two tires, your differential will be working a bit harder (as the older more worn tires have a slightly smaller diameter so will turn more times). Most car companies advise the amount of difference the system will tolerate on AWD models - typically a few 32nds of an inch of tread difference. So worth checking how worn your existing tires are. And last thought - if you use a different brand or tread style that could exacerbate the imbalance across the four tires.

My advice would be to go back to the dealer and ask why they should go on the same side. There is also a very helpful gentleman from Jaguar corporate on this board (Mike I think)? Perhaps he can advice on Jaguar's guidance on this for those of us with RWD as well as your AWD.

Am sure there are others on this board much more experienced with the AWD system who may be able to shed some light?
Good luck!

 

This dealer is making stuff up.

Jaguar's awd system doesn't have a centre differential. There is no need to worry about different sized tires front and rear as the system uses a set of clutch plates that are designed to slip at varying rates most of the time. The multiplate clutch unit doesn't lock up very often, it usually just slips. Most of the time it is completely open.

Unless you had staggered tires (different sizes front and rear) or directional tires then the pair of replacement tires should have gone onto the rear of the car.

Fitting worn tires and new tires to the same axle causes the differential on that axle to turn internally which is not the best situation.

This is a direct quote from the Owner's handbook for model year 2013:

Ideally, tires should be replaced in sets of 4. If this is not possible, replace the tires in pairs (front or rear). When tires are replaced, the wheels should always be re-balanced and alignment checked.

 

Thanks guys, but unfortunately since I posted my original question, it lost its practical aspect and became purely academic. As I was inspecting my tires to see if they were unidirectional, I found a major bulge on one of my left-side tires. So now I'll be replacing the other two tires as well. For whatever reason, this winter, roads in the Northeastern US resemble obstacle courses, or mine fields. Having low-profile tires does not help either. I think my next vehicle will be a hovercraft...

 

with the AWD system, you have to replace all 4 tires or, you will have a traction issue that can lead to an accident. If you could afford it, get winter wheels as well maybe some 18s. as long as you have more tire and less rim, you shouldn't have so much trouble with your car.