I recently got black deep dish bullitt wheels, 18x9 and 18x10. I was told that rear tires of 285/40/18 and front tires of 255/45/18 would fit well and that the car would not need to be retuned for the tires. The tires are about an inch anda half taller than the stock tires, however. I know this has probably been asked many times, but would it need to be retuned/how would one know how much to change it by on an sct. Also, is it bad to drive on these tires at all before we get the odometer issue figured out? Thanks a lot.

 

Actually the 285/40/18's are 27 inch dia tires just like the stock 235/55/17 pirelli's.....The 285 is the width of the tire in mm's and the 40 is the height of the tire as a percentage of the width(40% of 285 mm). Depending on the brand of tire it may vary very slightly. The tires have a spec know as revs per mile(revolutions per mile). The stock pirelli's are 768 revs per mile. 285/40/18 nitto 555's are 770 revs per mile, and bfg kdw's in that size are 771 revs per mile. You can adjust this if you have a tuner.........just see what the revs per mile spec is for the rear tire you have.If you don't have a tuner don't even bother.........being that you went with a 285/40/18 the difference is negligible............

 

correct, no change needed

 

+1

and the tuner only goes by fives if I'm not mistaken, so it will only be so accurate.

 

Yep, the SCT can only set Rev/Mile in 5 rev increments.