whats the biggest you can go on the stock rims for the 18's, i want to go wider but dont know how wide to go. Input is needed i need tires soon. Thanx guys

 

245/40/18 in front and 255/45/18 in back.

Lou

 

how come you cant go any bigger in the rear like 275/40's

 

Because the rear (and the front) is 8" wide. to use a 275/40 tire, 9.5" is the recommended rim width, and (9" to 11") is the rim width range. These measurements are per the tire manufacturers. If you used 275s on an 8" rim you would have severe tire buldge, and create an unsafe condition. A 255/45, on the other hand has a recommended rim width of 8.5" and a rim width range of 8" to 9.5"