Does anyone know if I would run into problems if I had different sized tires front to rear? In particular, I'd like to run 245/45-18 all seasons on the
front and 245/40-18 snows on the rear (about a 4% difference in circumference).

Will the TCU/anti-lock systems have any problem with that?

What about STRs they had different sizes f-r? But did the difference in
aspect-ratio make up for the tread width difference?

Oh, '08 4.2l
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Jaguar: Grace, Pace, and Space - Sir William Lyons

 

STR circumference / rolling diameter works out so they're (almost) the same.

At some point you'd be asking for trouble / codes but I don't know what the threshold is.

 

It will be a mistake not to run four snow tires on an S-type, assuming you have condtions that require ice/snow tires in the first place. Not much point being able to get traction if you can't stop or turn.

No idea how much difference in diameter the car can tolerate without setting off the ABS warning.

 

I agree with Mikey- snows all the way around- my STR would be un-driveable with all seasons on the front- going into my 3rd winter with my Blizzak WS70's and couldn't be happier!

 

The rear tires can be larger but I would not recommend smaller. The TRAC CONTROL 'might' assume that the slightly faster turning rear wheels need intervention and activate the TC.

When I worked at the dealer I had a car in for diagnosis (XKR) and the customer stated that the car would occasionally slow down on the hiway with the TC flashing in the INSTPK display.

It turned out that the customer had ROTATED the wheels/tires FRONT-TO-REAR and the slightly smaller tires in the rear were were enough to cause the TC to think they were losing traction!!

The rears can always go SLOWER but not faster (at least not by much).

I can't tell you that the ones you are referring to are enough different.

I don't know the exact difference that will cause problems.

bob gauff

 

I bet that was "fun" to figure out!