You can use the torpedo level to measure the floor. Subtract that angle from the measurement that you get off the wheel.
2004 330Ci 6 Speed; UUC Sway Bars; Powerflex RTAB's and FCAB's; KW V2 Coilovers; 3.38 OS Giken LSD
Z4 Finned Diff Cover; Headers; M-Tech II Rear Bumper and CF Diffusor; CF Trunk; CSL Front Bumper
M3 CF Hood; DICE I-Pod Kit; JTD Rear Shock Mounts; UUC Front Strut Bar; O2 Simulators
ESS TS2 Twin Screw Supercharger