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Tires - Originally Staggered, but dealer put the same all around

We’re purchasing a used 2009 Infinity G37 Coupe. The manufacturer sold it with a staggered setup, front 18x8 w/ 225/50/18 and rear 18x8.5 w/ 245/45/18. It has new tires but they are all 245/45/18’s. Reviewing the tire manufacture’s specs both the 8 and 8.5s are within range. The tire brand/model is not sold in the 225/50/18 size.

So the options are:

  1. Drive it with 245’s all around (low cost)
  2. Purchase to new front 225s of a different brand/model. (medium cost)
  3. Purchase 4 new tires 225s/245s of all the same brand/model (high cost)

Is it safe to drive w/ the same tires all around? The sidewall deflection will different between F/R.
I’m assuming the 8s should go up front, so there is more deflection on the fronts to promote understeer.

The “staggered” (mismatched) tires were originally installed to get the highest possible scores in magazine handling “tests” (skid-pad G-force measurements) which are then used to rate various cars in their comparison articles…So if you drive your car in competitive events or your driving style involves four-wheel drifting though the curves, the mismatched set-up will perform SLIGHTLY better. Otherwise, a matched set of tires should do just fine…The fact that the rear wheels are a half-inch wider should not cause problems as long as you don’t rotate the tires.

It will be my wife’s car. She has already said I’m not allowed to take it to autocross.

Caddyman is right.
Throw out option two. Mixing brands is a bad idea.
Suggest your wife try the autocross.

I suspect there may be clearance issues in the front - and that could lead to some rather dramatic results (read this as BAD)

The safe advice would be to get the vehicle back to the original configuration as best you can.

Is this an Infinity dealer, a used car dealer, or a car dealer but of a different brand car (not Infinity)? I think is very poor if an Infinity dealer is doing this, but any dealer is just trying to save some money.

The tires will handle differently because they are mounted on different width wheels. The imbalance might be slight or significant, only way to tell is actual track testing including wet and dry pavement testing. Since this isn’t going to be done, I’d tell the dealer to put the manufacturer recommended tires on the car.

If you’ve already accepted the car as delivered by the dealer, then I guess you are struck.

I think you should take them back and insist that they replace them with the correct size tires and you should only be responsible for any cost difference (if any) between the new tires and the ones they put on. Point out to them that any deviation from manufacturers specifications could make them liable in case of an accident.

Because the tires in front are larger than specified, this car could suddenly oversteer in bad weather causing a loss of control. You don’t need to be in an autocross for that to happen. If you have to go to another shop and pay for a whole new set of tires, do it and sue the dealer in small claims court, but you have to give the dealer a chance to make it right first.

In the end, your out of pocket should be low to nothing. BTW, did you check the speed and load rating of the new tires to see if they meet the specifications? All recommendations above are based on the assumptions that you did not specifically ask for those tires, or if you did ask for that brand/model, the dealer did not inform you that they did not meet the specs.

Tell the used car dealer that you are planning on buying this car from that you won’t buy it until they put on the correct size front tires on the correct rims. Make sure they put the 8" wide rims up front.

Then buy it.

BC.

The standard model Infinity came with 225/50/18 on all four corners. Decent performance tires in that size can be had for around $150 each. So you need two 8" wide wheels so you have a matched set, then you can use the standard recommended tire size on all four corners.

You can use Tire Rack’s web-site to work it all out…