The air conditioner died on the 5 series on the way back from Daytona. After about a year replacing everything but the blower fan, the blower fan froze up. That causes the fuse for the hvac system to blow meaning I lose outside vent air as well. I have decided to move on from rallycrossing the 5 series for now. It has been a wonderful journey and I haven't decided what is next for the car.
If anyone is thinking about rallycrossing an E28 in the future, here is why I am getting out of it.
Steering is too slow. I have to turn the wheel 360 degrees for every cone in a slalom. See: https://www.youtube.com/watch?v=rjVUBY6prOg. It is frustrating to miss an apex because I could not turn the wheel fast enough. A steering quickener or a steering rack could fix this but both bump you up to Modified.
Limited suspension options at stock height. I could not find an off the shelf set of coilovers that let me run at stock height. Stock shocks or Bilstein HDs are fine but the car needs a higher spring rate to work in rallycross. I don't have enough skill to put together a custom suspension myself so it would be pretty expensive.
I can't heel-toe downshift in the car because my feet are too big (size 15). Downshifts to first gear are pretty tough.
Second gear is too long. Ideally, it should top out around 55mph. This is solvable with a 3.64 or 3.73 diff but that bumps you up to Modified.
Adding up the costs of the the air conditioning repair and a custom suspension setup, I started looking for a new rallycross car. I took a serious look at second and third gen MR2s and E36 BMWs. I decide to avoid the standard Volvo 240/early RX7/E30/944 mostly for air conditioning reasons. I am not even close to fitting in a miata with a hardtop. There isn't much out there with RWD, independent rear suspension, and fits 15" wheels.
I haven't decided what to do with the car next. I am interested in trying drifting and the car fits nicely into Chumpcar. Both of these destroy the car. I am not sure if I am willing to do that yet. Apart from some cosmetic rallycross damage, it is a fairly nice 535is with a manual, LSD, and sport interior. I made the mistake of adding up how much the car cost me per month (insurance, storage unit for tire trailer, etc) so I will probably list it for sale soon.