[gtpvette]

Let me clarify,, trying to make sure I have enough space between inside face of rim to spring.

Looking at a new rim/tire setup as everything is on sale and I need new tires anyway. I need to make sure I don't rub the springs up front (no coils). Don't worry about poke

Current setup 17x9 +40 3MM spacer up front 245/40/17 tire 9.8 cross section

Thinking 18x10 + 15 285/30/18 tires 11.4 cross section


Going to work off the tire cross section (sidewall to sidewall) number as it's larger that the rim.

Backspace = (9.8/2) + 1.57 (+40MM offset) + .11 (3MM spacer) = 6.58


Backspace = (11.4/2) + .39 (+10 offset) = 6.09 or

Backspace = (11.4/2) + .59 (+15 offset) = 6.29


Math good? Or should I subtract the spacer in first equation which would then be 6.36??