What do wood, leather, rubber, steel, carbon fibre and ceramics have in common? Well, amongst other things, engineers have used them all in vintage motorcycle brakes. Many experts (in particular those you meet down the pub on a Friday evening, and who are reportedly faster round the Mountain Course than McPint) may tell you that braking is for losers. But sooner or later you are going to have to reduce your forward momentum. Sometimes shoe soles on tarmac just won’t cut it.
The First Vintage Motorcycle Brakes
Early vintage motorcycle brakes were scarcely better than the aforementioned shoe soles. To start with, designers often only deemed it necessary to put brakes on the rear wheel. Although in retrospect that might be just as well. What with having to constantly advance/retard ignition, manually pump oil around the engine and adjust speed via a lever on the ‘bars, grabbing a big handful of front brake might have been too much for many early motor-bicyclists.
In the early years, designers usually lifted brakes straight off the bicycles of the time. Those primitive brakes consisted mainly of wooden blocks or compacted leather pads that rubbed against the rim (or less frequently, on the tyre). Another common type of motorcycle brake in those early years also came from bicycle designs. The “spoon” brake consisted of a rod-operated, curved metal plate that would rub against the tire’s tread.
As engine performance rapidly increased, it became clear that this sort of brake wasn’t up to the task. The burning smell that didn’t come from the engine was probably a giveaway. The first refinement in braking technology came in the shape of a steel hoop on which the brake block would rub. The hoop was fixed to the wheel rim or to the spokes. The main advantage of this was that it offered a slightly greater friction surface.
The 1920s saw the arrival of drum brakes, as well as the first disc brakes. The latter technology didn’t immediately catch on, so drum brakes became the norm for motorcycles until the 1970s. In the 70’s, car-inspired disc brakes began to appear on road bikes. Racer and engineer Peter Williams’ famous “Wagon Wheels” Arter-Matchless G50 sported these vastly improved disc brakes first. They called his G50 “Wagon Wheels” because of the distinctive look of its cast wheels, with spokes recalling those of old horse-drawn carriages.
The first hydraulic discs used for vintage motorcycle brakes did not offer more initial stopping power than the best drum brakes of the day. But they did offer the advantage of not overheating so easily, particularly once cross-drilling became commonplace on the braking surface. This favours cooling of the entire system, not just of the disc itself. The holes also prevent the build-up of a fine film of water on the disc in wet conditions.
The Black Douglas Motorcycle Co., however, prefers to use cable-operated drum brakes on the Sterling. These are more in keeping with the style of our machine. They provide very satisfactory braking despite their small diameter, thanks to the very light weight of our machine. Of course, to be period-correct (the Sterling is, after all, an evocation of the flat-tankers of the 1910s) we should really use spoon brakes, but we don’t think this would cut it with current regulations. In fact, the latest batch of regulations might oblige us soon to use ABS-equipped disc brake systems!
Modern Motorcycle Brakes
The majority of contemporary motorcycle now use ABS-equipped hydraulic disc brakes. Engineers have vastly improved them since the late Sixties, when Peter Williams started using them on his racing machines. Cast iron has given way to steel. Discs are mounted floating or semi-floating. This reduces warping of the discs. Front calipers are equipped with four massive pistons. Rear calipers are smaller and usually have only one or two pistons. The entire system is equipped with ABS technology.
Brake pads have started incorporating high-tech ceramic compounds. Racing motorcycles use carbon brake discs, which can endure the extremely high temperatures caused by repeated heavy braking. The downside is that they only work well at a high threshold temperature, which makes them impractical for use on road bikes.
Looking towards the future, the appearance of electric motorcycles has led to the development of regenerative braking that, as its name suggests, uses the kinetic energy created by braking to store energy that can be used to recharge the vehicle’s battery pack. The stored energy can be used to provide extra acceleration on petrol-engine vehicles, like the KERS system used in Formula One. If the Black Douglas Motorcycle Co. decides to produce an electric Sterling one day in the future, this braking technology will definitely have its place on the bike.
Burt Munro – A Man With Little Interest In Brakes, & More Articles About Vintage Motorcycles
Burt Munro, who set a land speed record for under 1,000 cc motorcycles, was not so focused on brakes. His record, set in the 60s on an Indian motorcycle he had modified since the 1920’s, still stands today! The story of the world’s fastest Indian motorcycle is truly amazing. If you are a gear head, our article on the history of vintage motorcycle engines might interest you. While we are on the subject of vintage motorcycle brakes and stopping power, we should mention we’ve got an article on vintage motorcycle tires too. We’ve got plenty for you to read. On the other hand, maybe its time for a ride!
Marc Michon for The Black Douglas Motorcycle Co.