BGTS

I'm looking at getting a staggered setup of 20" AMR Charcoal wheels for my 06 GT. The rears are a +48mm offset and the fronts are +30mm offset. Does anybody have wheels with similar offsets that can confirm if I can run 285/35/20 tires in the rear and 255/40/20 tires in the front? I think they will work, but I want to make sure they don't rub. The previous owner of my car put on a set of 20" +24mm offset Shelby Razors with 275/35 tires all around and they rub on the fronts and occasionally in the rear too.

Bert

First, we need to know what car you have. Since you posted in the 05-09 section, I'll assume it is a 05-09 Mustang; if not, that is important.

Next, you need to find out what width the wheels are. Since you are looking at new wheels, the width should be in the ad or product listing. (for wheels that you already own, easiest way to do that is to take them off and look at the back, and the width should be stamped on there)

Knowing the width, we can confirm whether the offset is correct for the wheel width. Most likely it is, since they are from American Muscle and they do know what they are doing with wheel fitment for Mustangs. Offsets can vary a little but here is what I think is correct:
8.5" -- 28-31 mm offset
9.0" -- 35-38 mm
9.5" -- 41-44 mm
10" -- 47-50 mm
10.5" -- 56-57 mm
11" -- 62mm

Next, you pick tires that fit the wheels. If you look up the tires on Tire Rack, you can look at the "specs" tab to see the recommended wheel width range; and you want the wheels to be within that range, preferably the "measuring width" or wider.

Also check the tire diameter, in the Specs tab on Tire Rack. Then compare that to the diameter for the original tires, or the tires that you have now. The standard OEM diameter for these cars is 27.2" ; you can get away with a little bigger than that, depending on whether the car is lowered or not.

If you buy the complete set of wheels and tires from American Muscle, you can be comfortable that they will fit correctly; they are pretty good with that stuff. If you are not comfortable, ask them directly.

I think the problem with the Shelby Razors is that they do not have enough offset, which makes the wheel and tire stick out more than it should. That is very strange though because they should fit correctly, if the previous owner had ordered the right wheels for the car.

The offsets you listed seem about right for an 8.5" wheel in the front and 10" in the back. If that is correct, then I think 255 is borderline too wide for the front, and 285 is about right for the back. But don't take my word for it; look it up on American Muscle and Tire Rack to make sure.

BGTS

Thanks for the quick reply!
The car is a 2006 GT

The front AMR wheels I'm looking at are 20x8.5 and the rears are 20x10. American Muscle recommends 275/35/20 for the rear and 255/35/20 for the front. However, I was thinking about running 285/35 in the rear and 255/40 in the front to get the diameters closer to each other but I just wanted to see if anybody was running something like that. I don't know how noticeable the difference in sidewall would be between the 275/35 and 255/35.

I was originally going to go with one of their wheel and tire kits but I decided to spend a bit more on some better tires and I'm going to go with Michelin Pilot sport 4S rather than the Nittos or M/Ts.

m05fastbackGT

If you go by TireRack.com's website, the measured rim width for 285/40/20" tires is 10" which has a section width of 11.4" and overall diameter of 29" However, in my personal opinion, running a 285/40/20 tire is just a bit too tall at 29". Although you could consider 285/35/20's which also have the same measured rim width of 10" and overall diameter of 27.9" or consider 285/30/20's also with measuring rim width of 10" followed by section width of 11.4" and overall diameter of 26.8" which is nearly right at the recommended stock height/diameter of 27" However, I would more than likely go with American Muscle's recommendation of 275/35/20" tires for the rear, which lists rim width specs between 9-11" and section width of 10.9" with overall diameter of 27.6" which is just 1/2" taller above the recommended stock height of 27". For the front, you can go with either 255/35/20" as American Muscle recommends which lists rim width specs between 8.5-10" with section width of 10.2" and overall diameter of 27" which is stock recommended height or 255/40/20" also with rim width range specs between 8.5-10" and same section width of 10.2" However, keep in mind the overall diameter for the 255/40/20" tires are 28" in diameter which are just slightly taller over the 285/35/20" rear tires and approx 1/2" taller over the 275/35/20" rear tires. Therefore, I would once again follow the recommendation from American Muscle, as they know what the correct tire size specs are for their AMR brand wheels. In the meantime, best of luck and welcome to TMS