I posted this over in the Tires forum. But I figure we've got more practical knowledge over here.

Hope someone has the answer. My head explodes when I try to calculate it.

This is for my auto-x/track days applications only.

I have a lowered 06 MCS with 15x7 Kosei K1-TS wheels (38 mm offset). Tires are 225/45-15 Hoosiers - A6 or R6, depending on the event.

Front camber -2.3 to -2.4. Rear -1.3 to -1.4.

The Hoosiers rub slightly on the inside. Using spacers from 3 mm to 5 mm cures the problem. I typically use 5 mm because of the quality of the available spacer.

So my effective ET is 33. But I know it could be 35, from experience with the 3 mm spacers.

Therefore, it could be said that any offset from 33 - 35 is known to work on my car with the 15x7 wheels.

I'd really like to get 15x8 wheels for these events.

Assuming the exact same tires - Hoosier 225/45-15s - what is the offset I need for 15x8 wheels?

 

Ask Minihune. He is the wheel and tire KING.

 

Thanks!

I sent him a pm, but as I told him, he's welcome to post his answer here.