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Staggered wheels size recommendation 99' Mustang GT

Looking to stagger the wheels on my 99 mustang GT. Anyone done this and have size recommendations? Thanks!

Don’t do it. But if you have to a Mustang Forum would be better.

I would not do that for a vehicle that is not going to be for track use only. You will have the cost of wheels and tires and will not be able to rotate them . Plus what if you have a flat then you might have 3 different sizes on the vehicle.
I would spend the money on four upgraded tires to get the handling you want.

@Mustangman and @CapriRacer are more qualified than I am to give actual real world advice so they might jump in here .

If this is a daily driver I don’t recommend it. My Mustang came with staggered wheels from the factory. Earlier this year, I bought a set of wheels so I could go to a square setup and get more than 12k miles out a set of tires.

99’s don’t really have much more space in the rear than the front. They don’t look any better with bigger rear tires (IMHO) and will handle worse because the greater rear grip will make the car understeer more. Cobra’s came with 245/45/17 on all 4. That is a lot of tire. You might get away with as big as 275/40/17’s on 17x9 inch wheels with about 25 mm positive offset but you might have to roll the fender lips a bit.

But don’t go staggered, you can’t rotate the tires to even out the wear.

My car came with factory staggered setup, 18" Front & 19" Rear and it’s just a PITA

They can’t be properly front to back rotated so they wear differently and finding matching tires has become more difficult.
Right now the front tires have plenty of tread, rear tires need to be replaced but the manufacturer has discontinued the tread design so I’ve got a choice of running mismatched treads or throwing away 2 perfectly good, expensive tires.

On a 2-wheel drive car, it is only necessary for both front tires to be identical, and for both rear tires to be identical. It is very common to see different brands on the two axles, and I have frequently bought tires two at a time.

Ah …… Mmmm ……. Not exactly.

Ya’ see, if the fronts react enough differently than the rears, the vehicle will try to swap ends in emergency maneuvers - and the driver won’t know that until he has to perform an emergency maneuver (and then it’s too late).

So it’s best to get tires that are as alike as possible. I am not a fan of staggered fitments, even in race cars. But at least with race cars, there’s room to make a mistake and recover. The key to avoiding problems is testing, which burns off a set of tires, something usually not done for a street car…

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Kindigit loves rear wheel tubs. 12-13” wide tires. Might need it with 700hp motor. A 99 gt does not need it.

There are good reasons to do this, BUT, you will need a degree in mechanical engineering and a LOT of test equipment to get it right.

The tires that came on your vehicle were selected by engineers who have access to a lot of test equipment and test tracks to give you a well balanced vehicle. Keep in mind that this is a system that includes more than just the tires. The springs, shocks, sway bars, alignment values, control arm designs and frame designs are all part of an integrated system. You change one thing and everything else is affected, sometimes not to the good.

The reason for the wider tires on the rear are for solid rear axles. As the vehicle rolls or sways, it unloads the inside rear tire and puts more pressure on the outside rear tire. In a factory system, the rear usually has less anti-sway control to minimize this. If you put larger tires on the back of a stock system, you will create a vehicle that will understeer more.

So if you go to a stiffer anti-sway bar alone and don’t change the tire size, you will oversteer. You will need to match the tire size to the new anti-sway bar to get back to neutral. While your at it, you may also want to change out your springs and shocks to lower the vehicle for better handling, then you may have to cut out part of your fenders and add fender flairs. That will then lead to new front and rear spoilers. Can you match all that on your own?

If you are willing to spend a lot of Benjamin’s on this project, there are kits that come with everything you need to have a high performance handling vehicle. You could buy a new car for the price of some of them. Then you will need to upgrade the engine, transmission, rear gears etc.