John Veninger

I'm going to flare my front fenders and switch over to wide 18" wheels.
Currently have:

17" x 9.5" w/ a 73mm offset

Switching to:

18" x 12" w/ a 40mm offset

By my math this should place the inside of the wheel at the same place with a need for 2.5" of outside fender clearance, correct?

flash968

watch out for inside clearance too - as the suspension goes under compression, the inside becomes a huge issue - check the geometry under compression

determining clearance is not limited to the rim size - you also need to check the cross-sectional width of the particular tire you are going to use (they vary from brand to brand, as much as an inch in these widths, so don't assume the tire size equals physical size)

to answer your question though, you're increasing rim width by 63.5mm - half will go inside and half outside - that means a 31.75mm shift - you have moved your offset outward by 33mm - 33 plus 31.75 equals 64.75 or 2.54" of additional outward shift of the rim alone - yes, your math is right

John Veninger

I'm just trying to move most of the extra width outward. My current setup with the w/ 275 Hoosiers doesn't need a spacer, but I'm sure I'll need a few mm depending if I run 305's or 335's.
Thanks for checking my math