What Parts Are Replaced During a Drum Brake Job?
Mark: Hi, it’s Mark from Top Local Lead Generation and we’re here with Mr. Bernie Pawlik of Pawlik Automotive in Vancouver; so far 16 time winners of best auto repair in Vancouver. If you want your place, if you want anything serviced on your car, these are the guys to see and we’re going to talk about drum brakes today. How’re you doing Bernie?
Bernie: I’m doing well.
Mark: So what parts are replaced during a drum brake job?
Bernie: Excellent question, so drum brakes are quite a bit different than disc brakes which we talked about in our last hangout. Drum brakes they actually, instead of having a brake rotor and a brake pads they use brake shoes and a brake drum so I’ll just get right down to looking at some pictures because they say a picture is worth a thousand words. So I apologize, this is a very tiny little picture, about the best I could find but it shows, you see the brake drum and I know it’s small to look at, you might need to get your reading glasses or magnifiers out but the brake drum, that sits over the brake shoes and the wheel is bolted up to the brake drum so I’ll just move on past this picture. There’s an illustration basically of what is inside the brake drum, so these are stationary parts, they sit stationary, the drum rotates around the brake shoes. The brake shoes I’ve marked with the red arrows and these are a frictional material like a brake pad, they’re designed to wear out but they wear out at a slow rate so that’s, that’s the main component that wears out as they press against the brake drums so like a brake rotor which wears out over time, the drums also take abuse and wear and brake drums usually need to be machined or replaced. Usually with drum brakes we can machine them more frequently than with brake rotors, they tend to last longer, there’s often less at stake with drum brakes because most cars use drum brakes on the rear unless it’s a truck where there’s a lot of weight on the back. Drum brakes are really just to provide a very small amount of braking to a car but it’s important to keep the car stable and slow it down but they, they don’t take the abuse and wear that disc brakes do so we can often machine the drums, they often take very little wear but just machining them so there’s a nice smooth flat surface.
So some of the other parts that I’m pointing out in this illustration, the green arrow points to a very important component, that’s the wheel cylinder; now this is kind of like the caliper on a disc brake. The wheel cylinder actuates the brake, it’s connected to the master cylinder, there’s fluid flowing through it when you push the brake pedal, there’s pistons in the wheel cylinder that are forced out, they force the brake shoes against the brake drum and that’s what slows your car down. The yellow arrow points to the self-adjusting mechanism, these are different in many different type of brake systems but all, all disc, all drum brake systems with one exception which I’ll talk about later have self-adjusting mechanisms because as the brake shoes wear they have to travel further and further into the brake drum and if they don’t have a self-adjustment mechanism the brake pedal goes lower and lower to the floor eventually you may not have any brakes at all; so that’s why the self-adjustment mechanism is there. The blue arrows point to the brake hardware, these are springs, hold down pins and items that generally get replaced when we replace the brake shoes, they stretch and move all the time and tend to wear.
So those are the major components of the drum brake system and as I said the shoes wear most frequently along with the drums needing to be resurfacing or replacement.
Mark: So out of all these parts which need replacement?
Bernie: Well the brake shoes. Most commonly the items where the red arrows are pointing, the brake shoes will almost always need replacement. The blue arrow items the springs and hardware need replacement, the self-adjustors usually last a long time however, they do need, they do need servicing and that is a key component of any brake job that we do. We always take everything apart, we clean it, we lubricate it, because these parts move just subtly but it’s important that they have the proper lubrication.
Mark: There’s a black arrow there, you didn’t mention anything about that. What’s that pointing to?
Bernie: Yes, that, very good point. That’s the parking brake lever; so many, many drum brakes, most drum brakes are found on the rear of cars these days, they haven’t used drum brakes on the front of cars since probably the very early 70’s. So the parking brake is actually a mechanical system and it has cables that connect to the pedals or your lever that you pull in the car and that black arrow points to the lever that actually pulls the brake shoes so it just, it just mechanically pulls the brake shoes against the drums.
Mark: So is there any extra servicing needed for the parking brake?
Bernie: Yeah, so the parking brake, one thing we do with the brake inspections is actually inspect how the parking brake is working and when we take the drum off we actually move, pull the parking brake lever, push it to make sure the cables aren’t seized because the cables will seize up occasionally and that will cause the brake shoes to wear out but other than that it’s mostly just requires that the lubrication that we do with any brake service. Speaking of parking brakes there are a lot of vehicles that have four wheel disc brakes, we’ll use a drum brake exclusively for the parking brake and this is a much simpler than the illustration that you’re looking at in that it has the lever, it has the shoes and it has an adjustment mechanism but it does not have a wheel cylinder as it’s not hydraulically actuated so it’s a much simpler version than this, doesn’t need service very often, you know if you have a car that’s 10 years old you may never need to do a service on the parking brake, really depends on, we just generally look at these, if it needs to be serviced we do it or if there’s some problem with the brake then we’ll replace it.