Book excerpt: The Complete Book of BMW Motorcycles offers a thorough year-by-year guide to every production machine ever built by Germany’s leading motorcycle manufacturer. From the first model, the 1923 R32 that launched BMW's motorcycle dynasty, to the latest (and fastest) superbike, the S1000RR, this book captures nearly a century of motorcycling excellence in a combination of historic and contemporary photos. Technical specs are provided for each model. This comprehensive review covers all of BMW's bike families: The side-valve machines from the early years The early overhead-valve performance bikes The modern Airheads and Oilheads The four-cylinder and six-cylinder touring bikes The early pushrod singles The modern overhead-cam singles The latest parallel twins, and inline-four cylinder sport bikes Among them, you'll find all the classic bikes—pre-World War II BMWs like the R5 that defined performance in that era; the military R12 that carried the Wehrmacht as it blitzkrieged its way across Europe; the Earles-forked R69S that offered the perfect platform for mounting a Steib sidecar; the R90S café racer; the K1 “flying brick”; and the GS (Gelände Sport) series that launched a dual-sport revolution right up to today’s world-class S100RR and retro-inspired R nine T. Like the other titles in Motorbooks' Complete Book series, this guide to BMW's motorcycle output offers the most complete reference to the subject available.