The FE Widebody Kit is a direct development from Evolution Racewerk's 135i Time Attack Race Program. They found out very early in testing and development of the 135i that it had an understeer problem at the limit. This was odd considering that the car is RWD which typically exhibits an oversteer characteristic. Even with suspension upgrades like springs/shocks and sway bar upgrades, the problem still persisted. After further inspection and testing, they found out that the main problem lies in traction, namely front wheel traction. The 1 series, being small and lightweight compared to other BMW series like a 3 series make it an ideal choice as a track car. However, one of the compromises of being smaller is that it features a smaller track (width). The front track on the 135i is 58.4" versus the 335's 59.1". The 135i's small chassis and subsequent short track (width) along with small front fenders dictated BMW to use a narrow 7.5" front wheel and tiny 215/40/18. On the rears however, a 8.5" wheel and 245/35/18 tires were used. A wider wheel/tire will offer more contact patch with the ground thus offering more traction. With the front tires being so small compared to the rears, the rear end would have more traction than the front, promoting an understeer condition. Also, for the weight and power of the car, the front 215/40/18 tires are far too undersized. In hard turns, the front tires would lose traction at the limit. This caused the front end to slide towards the outside of the turn, in effect causing an understeer condition. Even though the rear end would rotate in the corner like a RWD car should, with the front end understeering, the car would not rotate and "pushes" to the outside of the corner instead of rotating into the turn.
Now, some of you will say that your car does not understeer and that you can induce oversteer on your car easily. That may be true as with enough power and/or rapid weight transfer on any RWD car, you can overcome rear traction and slide the rear end out in a spectacular cloud of smoke. However by losing rear traction to rotate the car, you are "scrubbing" off valuable speed in the turn. You will also be countersteering (turning the steering wheel the opposite direction of the turn) to keep your car in line. This process slows you down considerably and when in a race, ever millisecond counts. The fastest way around a corner is to have enough front traction so that the front wheels "steer" or rotate you through the turn instead of using the rear wheels to accomplish this. This will exhibit neither understeer nor oversteer, the ideal neutral handling condition.
On the rear end of the 1 series, traction is not an issue. There is more room in the rear wheel well compared to the front wheel well. With the correct offset (ET59-62), ER was able to fit a 10" wide wheel in the rear. With a 10" wide rear wheel, ER was able to run the maximum tire width in their racing class (which is a 285 wide tire) which increased their rear traction considerably. The front end, which was the original side with traction problems, was still limited to a maximum of a 8.5" wide wheel and a 245 wide tire. Even though now the car should have more traction all around, the original problem of the front tires not having enough traction versus the rear tires is still present so the understeer condition is still not solved.
To solve these handling issues with the 1 series, Evolution Racewerks built their FE Widebody Kit. They wanted the FE Widebody Kit to be aggressive yet subtle by following the styling lines laid out by BMW designers yet would allow ER to run a 10" wheel in the front and therefore a 285 wide tires as well. Since the factory wheels were 7.5" and ER wanted to run a 10" wheel, they increased the front fenders 2.5" (for a total of 5" increased width or track). This allowed ER to comfortably fit the 10" wheel and not have clearance problems. With the front and rear wheels squared up, running both 10" wide wheels front and rear with 285/30/18 Yokohama Advan Neova AD08 tires all around, the car exhibits a neutral handling characteristics in turns, the idea situation! Understeer has been virtually eliminated and rapid oversteer not an issue. With the basic traction issues resolved, ER could now focus on suspension tuning. Suspension (shock/spring stiffness), alignment and sway bar changes are now more responsive and predictable. Now, efforts i