Disc brakes are commonplace nowadays, but before 1970 most bikes had drum brakes, which are now in the minority due to the mandatory installation of ABS. It is important to remember the maintenance to keep them running well.
- Drum brakes will no longer be allowed to be sold except for moped type 1!?
- Oil is strictly prohibited, but lubrication of the necessary parts is essential.
- Set the return spring and then attach it to the brake panel.
Drum brakes will no longer be allowed to be sold except for moped type 1!?
The brake arm is the one you are touching with your military hand. As the brake shoes wear and the play is adjusted, the arm will gradually increase in collapse. Many models have an indicator on the arm and cam to show shoe wear, so pay attention to the position of the indicator after adjusting the play several times. If this is overlooked and the arm is pulled too far, the brake lining on the shoe surface will wear away and the shoe itself will touch the drum, damaging it.
To replace the brake shoes on a drum brake, the wheel must be removed. If your bike has a center stand, you can use a jack to support the bike, but if your bike only has a side stand, you will need to use a maintenance stand to hold the bike upright. As the lining wears down, brake dust will accumulate inside the drum, so be careful not to inhale it and clean the drum with brake parts cleaner.
Drum brakes have been used on the rear brakes of small-displacement vehicles, most notably moped scooters. However, have you noticed that they are completely missing from new motorcycles and scooters of 125cc and above? The Yamaha SR400, which was recently announced as the Final Edition and whose production was discontinued, also had a drum rear brake. It is clear from the world of racing that drum brakes are inferior to disc brakes in terms of performance and heat dissipation. However, with proper maintenance and riding at a normal pace on public roads, there are not so many situations where drum brakes do not stop.
The decrease in the number of drum brake vehicles is due to the revision of the safety standards for road vehicles by the Ministry of Land, Infrastructure, Transport and Tourism in 2015. This amendment requires thatABS (Anti-lock Braking System) to become compulsory for all new 125cc and above bikes launched after October 2018.For mopeds, ABS or CBS (Combined Brake System) is mandatory. ABS or CBS (Combined Brake System = front and rear linked brakes) became mandatory for mopeds, and mopeds were exempted from the amendment. Since motorcycle drum brakes are mechanically operated by cables and rods, they cannot be equipped with hydraulically controlled ABS, and at this point, the adoption of drum brakes on new models of 125cc and above was abandoned. Incidentally, automobile drum brakes are hydraulically operated, so ABS can be installed, and drum brakes are still used today.
The installation of the system will finally become mandatory from October 2021 for continuously produced vehicles that have been on the market since before October 2018.This will make it impossible to continue selling the SR400 with drum rear brakes. Incidentally, the rear of the early Kawasaki W800 model released in 2011 had drum brakes, but the current model introduced in 2019 has disc front and rear brakes and ABS in response to the law change.
ABS is a driver assistance device that protects riders from slipping and falling when braking hard in an emergency, and it is certainly safer to have it than to not have it. However, this does not mean that you can no longer ride disc-brake or drum-brake vehicles that are not equipped with ABS, so it is essential to carry out proper maintenance to ensure that each brake system is working to its maximum potential.
- Point 1: The mandatory installation of ABS on motorcycles 125cc and larger has made it virtually impossible to sell new mechanical drum brake vehicles.
- Point 2: For vehicles that have already been registered, both disc and drum brakes can continue to be used even if they are not equipped with ABS.
Oil is strictly prohibited, but lubrication of the necessary parts is essential.
This anchor pin is the fulcrum of a leading-trailing type brake shoe. Since the brake shoe is forced to expand by the cam, the pin and shoe do not stick together, but applying the proper amount of grease improves the operation of the shoe.
The brake cam that pushes the brake shoes apart, along with the cam surface that contacts the shoes, also requires lubrication of the shaft that is inserted into the brake panel in order to operate smoothly even with slight lever or pedal operation. If a felt ring is installed on the front side of the brake panel, do not forget to set it during assembly.
After washing off the brake dust with parts cleaner, use sandpaper or nylon abrasives to remove any foreign matter from the inside surface of the drum. If the drum surface is rusty after not being ridden for a long period of time, removing the rust with paper will ease the damage to the brake lining and improve the braking performance.
One of the most important maintenance tasks for drum brakes is to adjust the cable and rod play. Unlike hydraulic disc brakes, mechanical drum brakes do not automatically adjust the gap between the brake shoes and the brake drum, and as the brake lining (friction material) wears, the gap between the brake lining and the drum widens and the lever and pedal play increases. Therefore, whether cable or rod brakes are used, the adjuster on the brake arm is used to adjust the play to the correct level.
When the brake linings are worn and the brake shoes need replacing, drum brakes require the wheel to be removed, which is a big difference from disc brakes. If your bike does not have a center stand, you will need a stand or jack that can stand on its own with the tire removed.
In a drum brake, semi-circular brake shoes are set facing each other, and the shoes are pushed outward to adhere to the drum to provide braking force.Depending on how the shoe is moved, it can be classified into leading-trailing type and two-leading type. The most common type used on motorcycles is the leading-trailing type, which uses a single brake cam to extend two brake shoes simultaneously. In contrast, the two-leading type was used on racing machines before the advent of disc brakes, and on high-performance production cars in the 1960s and early 1970s, where two cams operate two brake shoes. If you look at the relationship between the brake shoes and the drum, in the case of the leading-trailing type, one shoe presses against the drum in the direction of rotation, whereas in the two-leading type, both shoes press against the drum in the direction of rotation, resulting in a stronger braking force.
In both types, the brake shoe is supported on both ends of the arc by an anchor pin and a brake cam.Oil is not allowed on the contact surface of the brake lining and drum, but the pin and cam need a good amount of lubricationHere is the grease. Grease used here is for smooth operation of pin, cam and shoe, and also to prevent squeal by suppressing vibration of brake shoe.
- Point 1 – For drum brakes, manually adjust the gap between the brake lining and the drum.
- Point 2: Appropriate lubrication with grease is effective for anchor pins and brake cams where brake shoes contact.
Set the return spring and then attach it to the brake panel.
Since the tension of the return spring is strong, the brake shoe should be bent into a V-shape and passed through the spring hole close together. If the old spring is rusty on an out-of-print or old car, there is a risk of breakage, so it should be replaced together with the shoe.
By applying high adhesion type brake grease on contact surface with brake cam and anchor pin, both lubrication and anti-squeal can be achieved. Be careful with low viscosity grease as there is a risk of sticking to the brake shoes.
Hook the V-shaped brake shoe onto the anchor pin and the end of the brake cam, and push it apart while applying equal force to the two shoes. Be careful not to pinch your fingers between the brake panel and the brake shoe.
When the brake shoes open, make sure the anchor pin and brake cam are seated in the correct position. Once the brake cam is removed for cleaning and greasing, set the brake arm on the cam, paying attention to the mounting angle.
The two brake shoes set opposite each other on the brake panel are attracted to each other by two return springs. Brake levers, brake pedals and brake cams also have return springs, but the brake shoe return spring is particularly important because if it breaks off due to age or other reasons, the shoe will open by itself and contact the drum, causing drag. If there is nothing wrong with the lever, pedal, cable or rod spring, but the response of the lever or pedal is light, or the brakes suddenly squeal, check the return spring of the brake shoes.
Adjust the lever and pedal play periodically, and replace the brake shoes when the lining wear finally reaches its limit. In a typical leading-trailing type, the cam and anchor pin are centered on theBy folding the two shoes inwards, the high-tension return spring can be easily removed without pulling on it.
The same applies when installing the new shoes. Before setting it on the brake panel, set the return spring beforehand and push down the V-shaped folded shoe over the anchor pin and cam. This way, you can install the shoe on the brake panel without having to worry about pulling the spring.
Even after ABS installation has become mandatory, drum brake vehicles sold to date can still be driven. Because these parts are directly related to safety, it is important to understand the mechanism and perform proper maintenance.
- Point 1 – A return spring with high tension is incorporated between the brake shoes facing each other.
- Point 2 – When attaching and detaching the shoe, folding it in a V-shape around the anchor pin and cam reduces the force to pull the spring.