Bolt-Pattern.com

Bolt-Pattern.com is a free online reference guide for wheel bolt patterns on cars. The site covers PCD (pitch circle diameter), stud patterns, wheel offset (ET), center bore, and stud thread sizes for dozens of car makes, from Alfa Romeo to Volvo.

Drivers can look up specs by make, model, and year before buying rims or aftermarket wheels. Measurements are listed in metric, with notes on converting bolt patterns to inches.

The site also runs a blog covering rims, wheels, and related car topics.