2012White5.0

I just pick up a set stock boss 302 rims for my 2012 GT and only paid $600. The rims had only been used for 300 miles, and look brand new . It feels like I stole them for that price.

I need recommendations for tire and size. Stock tires on the boss 302 are front: 255/40/ZR19, and the rears are 285/35/ZR19, but the sidewall just seems too thin and the diameter is about an inch less.

255/45/ZR19's on the front and 285/40ZR19's on the rears seem like they would look better and are much closer to the stock tire diameter, and revs per mile.

Ant advice on what tire size I should go with? I don't want the tires to be so big that I get sloppy performance.

ticopowell

What kind of performance? straight line or cornering?
you want more sidewall for drag racing and less for cornering, but either way between those two sizes you aren't going to see very much difference unless you are really good at driving your car.
Also it will change your shift mph and you will want to make sure your computer knows what size the tires are.

2012White5.0

Definitely want tires for better cornering. Looking online there is a 1.2% difference in the sidewall height from 245/45/19 to the 285/40/19. Which would mean the speedometer read 25, but I would be going 25.34 mph. So no need to recalibrate with the larger size.

The standard boss tire size is about 5% smaller, but speed difference is still negligible.

ticopowell

5% is noticeable to me.. but going 95 when you think you are going 100 could be a good thing in some situations... but it also affects the odometer so the car will show more miles on it than what it actually has.
so if you want better cornering go with smaller, but like I said you probably won't notice the difference. The biggest factor that you will notice will be the tire you buy, also you might not find it in both sizes so that might make the decision for you.