Hey all, I have some potential concerns that I'm trying to address as to the fitment of aftermarket wheels on my car. In boxes for spring, I have some American Racing Torq Thrust M wheels. 20x8.5 +32mm up front and 20x10 34mm out back. I'm concerned about the fitment of that offset on a lowered car. My car is lowered by Ford Racing K Springs, and that was a bit over 1.5" drop all around.

I plan on running a 255/35 up front, and for proper tire height, a 295/30 out back.

Can anyone give insight as to recommended tire sizes and offsets? I now what people put on their Mustangs runs the gamut, but wheel offset plays a big part, as does doing things that provide extra clearance.

The reason for my concern is due to seeing the fitment on someone's car that an a 275/35. A tire that is narrower, but also taller than stock as well.

These as two pics that show his rear wheel fitment. Luckily, he too is running K Springs.

 

the 295/30 will put your speedometer off by like 3% or something high like that. the 285/30 is <1% so it's a closer size to stock. plus 285 is, in my personal opinion, the best looking tire size for our stock rim. the stock 255's are narrower than the rim but the 305 (which is the next size up from 285 that has a sidewall ratio that is <1% diameter difference from stock) is way larger.

 

actually sweetie, according to math.....

the 255/40R19 is a 27.0" tire

the 275/35R20 is a 27.6" tire and is 2.0% too slow.
the 285/30R20 is a 26.7" tire and is 1.1% too fast.
the 295/30R20 is a 27.0" tire and is 0.02% too fast.
the 305/30R20 is a 27.2" tire and is 0.5% too slow.

Thus the logical choice for tire size would be the 295/30 which is a closer size to stock, with a negligible difference of height.

Some additional food for thought.....

the 285/35R20 that is STOCK on the 2013 GT500 is a 27.9" tire and is a full 3.0" too slow

 

Ok. I'm not a math kind of person. Is there a place where I can plug in numbers and get your results?

 

http://www.miata.net/garage/tirecalc.html

 

Your rear wheels are going to be 1" further out than stock Brembo wheels. Most people doing wide rear wheels go higher offset in the back to avoid the wheel poking out.

 

No choice here in offset, this is what they sold specifically for a fitment on our cars.

 

My suggestion would be differant wheels.

 

Wow, great advice.

Im going to be running 18x10 sve drifts on all four corners in a 285/35 or 30 for autcross purposes. I believe these wheels are close to the offset you listed. Its been posted that with these wheels with 285/45/18 on a car lowered 1.5" fit great. So Id infer you should have no problem with your setup...

 

Well I guess Ordie's car looks perfect with the K's and 275/35's... Im just concerned about the 295/30 and how the impact would be. Also being dead of winter I'm anxious as heck to get these wheels on, but it'll be a few months yet.

 

It sounds like you just want people to reassure you the wheels you got won't stick out... however, the offsets aren't ideal for running wide wheels and tires. There are some wheel offset calculators (search the 1010tires site). Unfortunately, the offset would be perfect if the wheel was 9.5". That extra .5" means it'll stick out .25" more than preferable.

Another way to look at it is the offset are nearly the same as RTR wheels but you're running .5" wider.

My suggestion if you really don't want it to stick out, sell/return them and find a better setup.

 

[QUOTE="TheDivaDanielle;6535449"]Hey all, I have some potential concerns that I'm trying to address as to the fitment of aftermarket wheels on my car. In boxes for spring, I have some American Racing Torq Thrust M wheels. 20x8.5 +32mm up front and 20x10 34mm out back. I'm concerned about the fitment of that offset on a lowered car. My car is lowered by Ford Racing K Springs, and that was a bit over 1.5" drop all around.

I plan on running a 255/35 up front, and for proper tire height, a 295/30 out back.

Can anyone give insight as to recommended tire sizes and offsets? I now what people put on their Mustangs runs the gamut, but wheel offset plays a big part, as does doing things that provide extra clearance.

The reason for my concern is due to seeing the fitment on someone's car that an a 275/35. A tire that is narrower, but also taller than stock as well.

These as two pics that show his rear wheel fitment. Luckily, he too is running K Springs.[/QUOTE

Fender flush offset for a 10 inch wheel is approx +38.

One example is super snake wheel which are +36.7 with a 275. They are flush and them some.

 

The offset you should use is around 35-40 front and 50-55 rear. The wider your rim go to the higher offset. The narrower your rim stick with the lower part of the range I gave you.