Tech Tips

Servicing Your Rear Drum Brakes

Written by  June 30, 2007

If your motorcycle is equipped with drum-style rear or front brakes, and your braking is sluggish, it’s time to address the problem. In the past, I’ve covered hydraulic braking systems such as pad replacement and servicing the fluid, but this month we’re going to discuss drum style systems. Drum brakes are still used on many models, and they require periodic maintenance, just like hydraulic systems.

When there is a problem with the rear brakes and they are not functioning like normal, the motorcycle must be raised off the ground either by jack or center stand, and the rear wheel removed. The bike we used for this demonstration is a 1983 Honda CB 550 that is equipped with a shaft drive system and requires only a few items to be removed in order to remove the wheel.

You must remove the rear torque link cotter pin and nut, and then slide the torque arm down to give access for tire removal.

After sliding the torque arm down, remove the rear axle nut, which in this case is a metric 22 mm. It’s a good idea to leave the right-hand pinch bolt tight because it will aid in the axle nut removal. After removing the axle nut, loosen the rear pinch bolt or simply remove it.

The next step is to lightly tap the axle shaft out of hub and remove the shaft. This particular setup is on the splines of the drive shaft and requires some wiggling to get the wheel out of the rear swingarm.

Once the wheel has been removed, you can lay all of the parts on a shop towel to keep everything together, which makes it easier to locate and reinstall the parts.

To access the brake shoes you need to remove the brake plate in the hub. Most of the time, you will find that significant brake dust has accumulated over the years or because of hard braking. Use compressed air in a well ventilated area to clean the shoes and plates. You should also inspect them for any abnormal wear or damage. If the shoes are worn past the normal specified limit, simply replace the shoes. This is done by removing the cotter pin and washer, pulling the shoes toward the center, and lifting off the plate. The plate has guide pins that are usually matched to the shoes, so check the manual if you have any problems.

Rust and corrosion can keep your brake shoes from returning to the stops on the plate. The brake cam should be removed from the plate and cleaned from time to time. This can be done with a wire bristle brush or a wire wheel on a grinder, which is what I prefer. Once this has been cleaned, grease the cam with waterproof grease and reinstall the cam and your existing shoes or new ones. In most shoe replacement kits the shoes and springs are supplied. If you are reusing the existing shoes, lightly scuff both the brake drum in the hub and the shoes to remove the glazing from use.

The last step is to make sure the brake shoes open and close easily when the brake arm is moved. If they are not opening easily and returning back with a spring force, remove the shoes and inspect all parts for binding.

There is an indicator that has to be placed over the cam and usually has a foam-type seal that must be installed before the indicator. Line up the dot on the cam and the brake arm and install the bolt and locking nut, if applicable. Reinstall the brakes into the wheel and mount the wheel back on the motorcycle. All the pieces you removed must be reinstalled in the reverse of removal, and make sure to adjust the torques according to your service manual.

This may seem like an overwhelming task, but it is actually a common maintenance procedure. So when your drum brakes are sticky, squeaky or simply not working correctly, you can follow these simple steps to service the brake drums on your metric, American, or British motorcycle.

This July 4th, please take the time to show appreciation for our armed service personnel. I appreciate what ALL of you do for our freedom in Iraq, Afghanistan, or wherever you may be stationed. I thank you All.

B-safe out there!

Dave Miller