Info from Korman:

• Differential Gear Ratio Changes
• Tire Diameter Formula

Info from UUC Motorwerks for E30 and E36 models:

• Wheel Fitments
• Tire Clearance

Tire Aspect Ratios table.

Wheel offsets is a list of offsets for various BMW and other manufacturer's wheels.

More wheels and tires. Click here for pictures of Genuine BMW wheels.