Many of us here on the forums use our BMWs for multiple types of driving. For us, our BMWs don’t just sit in the driveway/garage and go back and forth to the track, autox course or to shows. As much as that may be what we would ultimately like, we have to be sensible. So we subject our BMWs to the demands of daily use AND to the demands of those automotive events that we enjoy so much. For that reason, in order to ensure our cars are properly prepared for these varying driving conditions, we have to be extremely thoughtful and selective when choosing modifications.
Wheels and Tires
Mounting good tires and ensuring their contact patch with the pavement is maximized will provide enhanced grip with no dramatic impact on ride quality. I went with a square tire and wheel setup so that I could rotate them back in forth in order to extract all of the life from the tires as possible and get the neutral balance I was looking for. Front-end fitment was the challenge at this point so I went with the widest setup possible that I thought wouldn’t cause issues. Tire choice was limited as I needed a specific size for the setup to fit properly, but I am happy to say the Kumho Ecsta XS tires aren’t too bad for their price.
Wheels: OEM 264s – 18x7.5 (F) / 18X8.5 (R)
Bridgestone Potenza RE050A RFT – 215/40/18 (F) / 245/35/18 (R)
Apex Arc 8 - 18x8.5 (F+R) +45 Offset
Kumho Ecsta XS – 245/35/18 (F+R)
The Apex’s fit with just enough clearance (see picture below) between the strut and the wheel. If the offset and wheel width were any different I may have required a spacer for clearance, but I got away with it by a hair. Keep in mind that no fender rolling/pulling was required here either.
The next step was addressing the alignment. While our cars are fairly adjustable from the factory, I knew that dialing in more negative camber in the front would improve front end grip even more and playing with toe settings front and rear would allow me to tweak the cars willingness to rotate to my own personal preferences. In order to make the front end adjustable I purchased a set of Ground Control street camber plates which work for the E90 (2006-Up 3 Series) and E82/E88 (2008-Up 1 Series).
The GC street camber plates were designed keeping the street driver and track driver in mind while offering many of the benefits of a fully adjustable camber plates. Now I don’t work for Ground Control, but I can appreciate the thought that went into their design.
Here are a few of the things that I like about the design:
- Utilizes a urethane bushing and axial load bearing for reduced harshness (waterproof and replaceable)
- 26mm of camber adjustment
- Cool slot designs allow for side to side caster correction – not adjustable
- Components are anodized or zinc plated making them corrosion resistant
- Camber plates available for stock or 2.5 inch springs
What does all of this mean? Essentially it means you can dial in your suspension just the way you want with some very thoughtful features for the dual-purpose driver. Here you get a great bearing design to reduce friction, but also ensure the ride is smooth and silent. Cabin noise increased slightly, but by no means is it offensive. Steering feedback was improved as the soft, stock strut tops were replaced with a much more firm piece of hardware. They are corrosion resistant so they won’t rust and corrode away horribly if you aren’t very caring to them. Although you still should because they still can, the key word is resistant here. I had that happen on an old car of mine and it was not fun. And proper perches allow for you to use the camber plates with the spring you are using, whether it be a coilover spring or stock spring.
Disassembling the factory suspension was easy. The only part of the install that required some work was the bearing. Take a look at the pictures below. We had to trim the bearing in order to make sure the nut grabbed the threads on the top of the strut. Minus that, the install went smoothly. Fortunately Jack, the shop foreman and lead fabricator, has the experience and skills necessary to do a job like this. Check out his Subaru 3.3RS NASA ST-2 race car here
Jack does all of his alignments by hand and is very precise. He was able to get all of the negative camber I wanted and get my toe settings to my exact specs through adjusting the length of the tie rods. The rear end is pretty adjustable from the factory so he was able to get that dialed in nicely without any drama.
Here are my final specs:
Toe: 1/16th toe out
Camber: -2.2 degrees
Caster: Factory spec
Toe: 1/8 toe in
Camber: -1.5 degrees
Now the car behaves exactly the way I wanted it to! The car is very neutral and rotates nicely and predictably under throttle. Under sharp steering inputs the car bites down and dives in where beforehand it would just plow with understeer if you turned in to sharply and with a lot of speed. Overall grip is much higher. Steering feedback has been sharpened. The tire offset dramatically changed the balance characteristics of the car, the sticker compound increased overall grip significantly and the lower unsprung weight from the wheels and tires improved grip as the wheel and tire now move more easily with road imperfections. It may have even helped acceleration a little bit. All in all, I couldn’t be more pleased with the outcome resulting from these simple changes. Here are some pictures of the final results, a recent autocross I attended and a video of my “fun run” showing the newfound throttle on oversteer. Please excuse the stuff rolling around on my passenger foot area!