I just bought an 06 330i that I plan to autocross. I want to stay in a stock class by SCCA rules, and will run in a street tire class. Currently I am at the bottom end as far as suspension, wheels and tires as the car I bought does not have the sport suspension. So far I have not found what the actual differrences are for the sport suspension so that I know what I can change. I assume the shocks are different and I can do what I want with shocks anyway. Are the springs and sway bars different on the Sport? One of my fellow autocrossers (top guy but not a BMW racer) also told me that I need to go to a large sway bar. Any comments on that? I will probably get a set of 18" rims is 8" in front and 8.5" in rear the max I can do and stay stock? As for tires I had been running the Falken RT615s as they are realtively cheap and stick well. Any other recommendations there? I have most of the winter now to plan for this.
I'll give you info from a D Stock POV. You can change the shocks and front sway bar. I have Koni double adjustables on my '05 330i (E46 w/ZHP). In the ST classes I believe you can change the springs (plz double check that as I am not as versed in ST prep). I did go to a Racing Dyanmics front bar (I have a rear bar for sale, as well as a trailer hitch for my E46!). The rim size you quote is only for the ZHP cars. All the others were 17" (not necessarily a bad thing). I drove a 135i on the Dunlop Drizzia Star something or another. Very sticky tires, especially for an ST class. They kept up with my Hoosier Racing Tires.
I want to stay in D stock. However, my car only has the basic suspension, I should be able to upgrade to the equivalent of the sport suspension option (not the ZHP option) and still stay in D stock. The 18" wheels were also a part of the sport suspension option. I just don't know what the differences were for the sport suspension.
Just to clarify, there was a "Sports Package" and a "Performance Package." The 18" wheel came only with the Performance Package. I would assume the springs are different from the regular E46 to the Sports Package and from the Performance Package (which lowered the car by 1/2").
Sorry. That's different. I kept thinking yours was an E46. Like all current gen BMWs, it has the dreaded "Pig o' Matic" effect. Two bazillion pounds of weight.
I still need some help with what the differences are for the Sport Suspension and the basic suspension on the E90, so that I know what I can change and stay in the stock class.
You'll have to review what the sales brochures says are the options for each model. It may not be very clear. This will really only apply to the springs. The shocks are free to change, as is the front bar (you knew that). Wheels are about the only other thing. A parts catalog my help you decipher what springs are correct for the Sports Package, too. You'll need to find a friendly parts person to help with that. All of this may not be easy.
