We are converting to studs and I was thinking this is the time to add wheel spacers. These are the specs on her 2012 Cooper S wheels.
Offset: 45mm
Backspacing: 5.47" Bolt Pattern: 4-100
Weight: 12.8lbs.
16X6.5

we are running 205/50/16 Direzza Z2's. What is the most spacer we can use without going out of stock class?

 

Offset change is limited to +/- 6.35mm.

For more information:
13.4 Wheels on Page 72

http://scca.cdn.racersites.com/prod/...nd%20links.pdf

 

so 5mm spacers is a go!

 

The allowance is +/-7mm for next year.

I'm pretty sure the stock wheel offset is 48mm, so you've already got 3mm extra offset. You could only use 3mm this year, or 4mm next year.

You'd probably be better off going with 16x7" wheels rather than fiddling with spacers. You're allowed +/-1" diameter from this year, so I went -1" from 17x7.

 

the stock offset for a 16X6.5 is 40mm so I think I am maxed out already :(

 

I'm pretty sure the stock offset on 16x6.5 wheels is +48mm.

 

A spacer reduces the offset number. The site linked below shows OEM ET's of 42 to 48. I don't know of a source for what wheels were factory fitted in what years.


http://minicooper.wikia.com/wiki/OEM_Wheels_and_Tires

 

so if OEM 16X6.5's are 48mm and my new rims are 16X6.5 45mm what size spacer can I use this year legally if +/- 6.35mm is the allowance from stock? I want to get these wheels out to the corners as much as possible. Thanks for all your help guys

 

I am thinking 3mm is the most I could go legally this year

 

Does this answer your question?

 

do you think a 3mm spacer on each side is going to make much of a difference?

 

I don't think it'll make much of a difference. I do think it'll make a small difference, I was considering doing it myself until I got wheels with a small offset (43mm).