Street Wheel Offset Question

I'm in the market for new wheels that I can AX with on my e89 Z4.

The front wheels have a 29 offset and the rear wheels have a 40 offset.

Goal is to get a square setup and the same wheels / tires on every side. So basically that means I can only get a wheel with the offset 33-36?

Am I allowed to mix and match offsets?

Thanks!

The rule is that the wheels' offset have to be within 6 mm of the stock wheels.

So 33 on the back wouldn't be legal, nor would 36 on the front. The only offset that could go on all four wheels is 34 or 35.

However, are both your front and rear wheels the same width? non-original wheels also have to be the same width as stock. You can't even go narrower on the rears in order to achieve a square setup.

Ahh yes. I should have made the range even smaller. Good point. The Z4 does come with a stock setup with 8" wheels all around. I should probably look up the offsets on those wheels before buying a set of wheels.

I also could buy the same wheels and use spacers to make them fit in the rear.

Thanks!

Alrighty. The base Z4 comes with 17x8" wheels all around with offset of 29. So I can go from 24 to 34 offset.

Thanks!

We are talking about Street class autocross, right? Because if not, it probably doesn't matter.

Haha yeah should have specified that this would be under street.

Finding affordable wheels that work for street rules is proving to be not fun. Might end up just mounting the same sized tire on the staggered OEM wheels and call it a day.

To use the "Base Z4" allowances, you need to make sure you don't have anything on your car that wasn't offered on a "Base Z4" or basically, if your car could have been ordered with 29et 17x8's from the factory.

Tweaking wheel sizes within the street class rules is intentionally difficult it seems like, to discourage expensive experimentation.

Yeah, for now I'm going to wear down the stock tires that have 140 threadwear rating and then I'll just stick the same 200 rating tires on all 4 wheels. Front is 8" and rear is 8.5".

Street rules are just weird in my opinion. Strict on wheels and tires but then you can get $10K shocks and one roll bar replacement. But you can't change the springs... lol

nilfinite wrote: Street rules are just weird in my opinion. Strict on wheels and tires but then you can get $10K shocks and one roll bar replacement. But you can't change the springs... lol

There's some truth to this, but a lot of it comes down to it being extremely difficult to create a rule intended to limit costs that racers can't/won't find a way around. I believe an early version of the last major rules changes limited shocks to single adjustables, but you can still spend stupid money on those.

Will wrote:

nilfinite wrote: Street rules are just weird in my opinion. Strict on wheels and tires but then you can get $10K shocks and one roll bar replacement. But you can't change the springs... lol

There's some truth to this, but a lot of it comes down to it being extremely difficult to create a rule intended to limit costs that racers can't/won't find a way around. I believe an early version of the last major rules changes limited shocks to single adjustables, but you can still spend stupid money on those.

as it left the factory would limit costs tremendously.