ok so right now my rear rims wheels what ever you call them are 18X10.5 rim and i have 295/35 on them but im going with a 315 but i want to get a 315/40 or 315/35 and tire rack only has the 35 in a drag radial... i really dont want to go with a 30 side wall... is there any place that make those two measurement tires? that are street not for drag radials or compition?

 

a "30" side wall is just a proportion of the width, the wider the tire, the taller the sidewall for a give ratio. my rears are 335/30/18, and are a hair taller than the front 245/40/18's.

as for 315/ /18 tires, they are few and far between.