According to the TIS service disc ...

Camber deviation may be caused by:
- insufficient spring force
- faulty rubber mounts in the rear-axle carrier
- faulty rubber mount in the control arm
- deformed rear-axle carrier
- deformed control arm
- distortion in the floor assembly.

For the E36 on standard 15" wheels and on standard suspension, the distance between the lower edge of the rear wheel arch and the rim flange at the bottom middle should be 510 mm ± 10 mm. This distance differs according to wheel size (up to 17 inches) and suspension type (standard/low-slung sports/rough road package).

HTH