View Full Version : 17x8.5 ET30 what will be needed..

05-10-2010, 01:00 PM
Hey guys,

I'm from the UK, i currently run a car with a 1.75" drop roughly. -2 camber all round , 17x8 ET38 with a 225/45/17 tyre and rolled rear fenders. I have no rubbing currently.

I'm changing to a 17x8.5 ET30 with a 215/45/17 in the rear, Can anyone tell me if i'm going to encounter problems or should the slighly stretch put me in roughly the same position as i am now?

Cheers guys,


The car,



The new wheels


05-11-2010, 08:54 PM
From my calculations you should be 9.35 mm more negative. Meaning your tire will stick out 9.35 mm more than the old set up.

8" x 25.4 = 203.2mm wide wheel
203.2 / 2 = 101.6mm -38mm = 63.6mm from your mounting surface to the outside of your wheel

8.5" x 25.4 = 215.9mm wide wheel
215.9 / 2 = 107.95mm -30mm = 77.95mm from your mounting surface to the outside of your wheel

77.95 - 63.6 = 14.35mm more negative with just the wheels

the 215 is 10mm narrower so 10 / 2 = 5mm less tire or positive offset

so 14.35mm - 5mm = 9.35mm more negative than the old setup

This calculation assumes your tires are their stated size. Tires are not always their stated size. For exact specs see the manufacturers actual measurement specs for the tire.