tire size?
 

anyone know how big i can go on tires before i start to rub. the torsion bars are up now. i have a 2004 gmc 2500 hd

I had 285/75-17 on my 06 without any issues so maybe 305's or 315's

Are you going to use the stock rims? A 285/75R16 will fit and may rub when turning hard, but the 6" wide stock rims make the tires wear funny. Once you get a wider rim it may start to rub more because now the tire is wider too. There are a couple of tire manufactures that make a 255/85R16. This size is close to the 245 width that came stock, but is much taller like the 285. The 255/85R16 in load range D holds the same weight as the stock tire in load range E. 305's will rub.

ive got a 315 70 17 on an 05 and all ive got is cranked torsion bars and all i had to do is trim the plastic inner fender wells and the front valance under the bumper