Most of the older classics (pre 1975) used drum brakes. Even as disc brake systems became popular, many manufacturers kept the rear drum brake due to their ease of manufacture and, therefore, their low cost. With few moving parts and low maintenance requirements, the drum brakes were popular with owners too. It was the late 70s before disc brakes became the way to go for motorcycle braking systems, and even then some of the disc brake systems gave very poor performance in the wet.
Classic owners who cover only a relatively short distance each year will rarely need to inspect their drum brakes. However, it is advisable to inspect the drums and shoes once a year as a precaution. Inspection is particularly important if the bike is ridden in wet conditions, as the drums are not fully sealed and water mixed with brake dust will impair the braking performance.
Replacing Brake Shoes
The front brake shoes will wear out first as they will be used most (or should be). To replace them, the front of the bike must be off the ground which, in most cases, is simply a matter of putting the bike on its center stand. Before lifting the bike, however, it is good practice to back off all the fixings such as the spindle or wheel nuts and clamps as applicable. It is much easier to back off these items with the bike's weight still on the wheel. The front brake cable should also be backed off.
After the bike has been lifted onto its stand, the spindle etc. can be removed and the wheel taken out. The brake plates on most machines follow a basic design of the shoes pivoting on a round stud at one end and being forced open at the other by a cam-shaped lever. The shoes are pulled down against the pivot and cam by a spring at either end. Twin leading shoe brakes have two cams that are linked and operate on both ends of the shoes.
Safety gloves (mechanic types) should be worn when removing the shoes as the spring pressure holding them in place is very high. To remove the shoes, the plate should be placed on a suitable bench with a soft surface or with a shop rag to protect the surface (especially on aluminum plates). The mechanic should then firmly grip the shoes and twist them away from their pivots.
Greasing the Pivots
Before fitting the new shoes, the cam lever should be removed and cleaned as should the through hole in which it is located. A small amount of grease should be added to the shaft where it passes through the brake plate pivot. A small amount of high temperature grease (marine type is best) should be applied to the shoe's pivots where they come into contact with the cam.
Refitting the shoes is simply a case of reversing the removal process. That is, attach the springs to the new shoes, then place one shoe in its correct position on the plate before levering the other shoe into position. This process must be done with a firm grip due to the spring pressure, again wearing suitable gloves.
At this point, the brake shoes and steel drum liner must be cleaned with brake cleaner to remove any fingerprints or grease.
Reassembling the wheel back into the bike is a reversal of the removal process, except that the brake should be applied to centralize the shoes before the wheel spindle etc. is fully tightened.
Once the wheel and brake has been refitted to the bike, the lever can be adjusted to give the correct height and free play. Typically, manufacturers recommend 20 to 25-mm (3/4" to 1") of vertical movement on the lever before the brake begins to bind on the drum.
Some classic motorcycle had hydraulic drum brakes and the system on this design must be bled after fitting new shoes. (See the article on brake bleeding.)
The efficiency of the brake will be slightly below ideal when it is first applied and the rider must allow for a certain amount of "bedding in." To speed up this process, the rider can apply the brake reasonably hard (with great care and allowing for road conditions, and other road users) a few times on the first ride after fitting new shoes.