Drum brakes were on the way out as the default method of stopping a motorcycle by the early '70s, certainly when it came to the front brakes on big sportsbikes. By the mid-'80s they'd fallen out of favor at the rear too.
However there are still plenty of motorcycles that rely on the once ubiquitous drum brake, especially at the rear wheel.
Some of their poor reputation compared to disc brakes can be attributed to the fact that they were often poorly maintained. Certainly for some time in the early days of disc brakes, drums often performed better next to stainless steel discs and non-sintered brake pads.
The reasons for poor maintenance are the usual ones. A drum brake's mechanism is largely out of sight and performance tends to go off gradually. It is also a lot easier to just drop an new set of pads in and change the fluid on a disc setup. There's no wrestling with reluctant brake shoe return springs and less filthy dust to deal with.
No more excuses – give your drum brakes what they deserve! You will need the following tools for the job, circlip pliers, workshop roll, small vernier caliper, brake grease, nylon abrasive pad, nylon-faced hammer, large vernier caliper, brake cleaner and a paint pen.
Check the action of the brake actuating arm by pulling the handlebar lever, or foot pedal. It should be easy, smooth and progressive. Also, the actuating arm should not form an angle of less than 90 degrees with an imaginary line through the operating cam and the drum center.
We really don't want to see any cables damaged. The protective coating has disappeared from the steel outer cable. This means water can get in and corrode the inner cable, rusting it to the outer. Check cable nipples for security and exposed parts of the inner for kinks or fraying.
Take the wheel out and have a look at the braking surface on the drum inner. If your motorcycle have been standing for some time there will be a layer of rust to remove before looking up close for major scoring and cracks. Most of the time cleaning is all what is needed to be done..
The shoes themselves can be in a pretty manky state. Generous application of brake cleaning can reveal the friction material to see in which condition it is. Be careful when working on older brakes or ones that haven't seen any maintenance for years as the shoes could contain asbestos.
Check that the thickness of the friction material matches the figures in the workshop manual. Irregular thicknesses mean that the shoes aren't making proper contact with the drum. You should buy new once in that case.
Remove the shoes so that the inside of the brake plate can be cleaned and the operating cam and pivot points can be lubricated. On our motorcycle the brake plate has circlips on the pivot points. With these removed, the shoes can be liften and folded inwards to take them off the brake plate.
Prior to removing the actuating arm from the brake cam, make some marks on the spindle and the arm so you can re-establish their relationship to each other on reassembly. Some motorcycle already have a helpful punchmark that lines up with the split in the arm.
On most motorcycles we have seen the spindle and cam were pretty grotty with ancient grease and brake dust caked onto them. The hole the component turns in on the plate is often very filthy too, as well as the spigots the shoes pivot on. At this point the can of brake cleaner is used fully.
Ordinary high-melting point grease will suffice at a pinch, but it's far better to use a brake-specific product. Whatever you choose, use sparingly and keep well away from friction surfaces. Refit the shoes and springs checking everything is correctly located.
Don't forget to clean and grease all the little clevis pins plus the pivots at the handlebar lever and/or foot pedal, cable balance boxes, rods and what have you. Don't use copper grease on moving parts as it's abrasive. Give the cables a good oiling too. Your motorcycle will stop better than it has for years.