More Than just Brake Pads – Doing Brake Repair Correctly

Subaru brake pads installed

Quality brakes pads make (or break) the brake job

When people think about brake repair, replacing brake pads is usually the first thing that comes to mind, but that’s not all that’s important. Don’t get me wrong. Using genuine brake pads purchased from a dealership is probably the most important aspect of a quality brake job, but without adequate attention to detail and knowing what to look for, it’s easy to make a mistake that will lead to unsatisfactory performance: short service life, brake pedal pulsation, squeaking and other brake noise, and uneven braking and pad wear.

It’s also very important to know that every brake repair needs to have several items addressed: cleaning, lubrication, and correction of rotor parallelism issues.

Subaru brake pads

Use the best brake pads!

If you don’t want brakes that fade, have poor bite when cold, wear out quickly, or make annoying noise, buy genuine brake pads from a dealership. Do they cost more? Typically they do. Are they “better”? Typically they are.

When deciding what make brakes “good”, you have to consider what’s important to you. For instance, if I wanted the best brake pad for racing, buying a Genuine Subaru pad set might not be the best choice. However, when a brake pad is very good at one thing, like fade resistance, it loses other positive attributes, like the ability to stop well when cold. When it comes to making a brake pad that’s pretty good at everything, buying the pads from a dealership is usually the best bet.

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Molybdenum Paste

Doing brake work right is more than just buying good brake pads and bolting them in. One important aspect is using the right grease. What’s the best grease to use for brake repair? Well, it depends where it’s going. There are three types of grease used in a good brake job.

Thick moly paste is only for the back of the brake pads and brake pad shims. This type of grease is too thick for lubrication. Its job is to dampen the vibrations that create brake squeal. Most manufacturers will include a packet of this thick gray grease in the box with the brake pads. If the pads don’t come with moly grease, then Honda sells tubes large enough for 100 brake jobs. Honda calls it M77 assembly paste. Of the moly pastes available, this is the one most like what comes in the packet with new pads.

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Copper Grease

Another type of grease is used for the pad sliders on the caliper brackets. Absolutely never ever use the packet of moly paste on the caliper sliders. This is a very common error. It won’t cause the brakes not to work or anything, but it will cause the pads to bind in the calipers. You’d be much better off putting nothing at all on the sliders.

I like the copper grease that comes with Toyota brake pads and Subaru brake pads. Nissan used to make a bulk container of this grease, but they no longer do. It was an enormous jar so I’ll never run out. I’ll probably end up passing the tub of grease on to my children. Ah the perks of being a mechanic’s daughter.

Silicone brake caliper grease is important to keep the pins moving freely

Caliper Pin Grease

Caliper pins must be cleaned and lubricated every single time the brake pads are replaced. We once had a mechanic work for us for a short time. He did a brake job that didn’t work out so well. We found one of the caliper pins seized when it returned. When we pulled him aside and asked what was going on he said that he didn’t lube the pins “unless they needed it”. So in other words, unless the pins were already binding, he didn’t do anything to them. And since the pin was bound, he clearly didn’t even do that. Sadly, this is a very common attitude in the auto repair industry. I frequently find cars with frozen pins and 3 newish brake pads and one worn out pad.

Just like the other brake lubrication area, the pins require a particular type of grease. Silicone grease is best for the pins. It can handle high temperature. It won’t damage the rubber boots and pin anti-rattle bushings. Once again, never-ever use the moly paste for anything other than the brake pads shims. Moly grease will cause the rubber to swell and the pins to bind.

scraping corrosion from rotor hub face surface

Machining Brake Rotors

I started writing this section and it started turning into a long technical article that most people won’t want to read. It’s here if you want it.

I’ll try to focus on what a consumer needs to know. First, when the rotor is mounted to the lathe, it must be mounted so that runs true. If rust or debris is left on the hub face, the rotor will wobble on the lathe. When it is cut straight on the lathe, it will wobble on the car. This is bad. There will be no noticeable problem at first, but after the car has been driven many miles, pad material will accumulate on the high spots and a brake pulsation will develop.

Why machine rotors at all?

Let’s go back to the hardwood floor and rubber shoes. You know those black marks that appear when someone squeaks to a stop? That’s a thin layer of sole material deposited on the floor. The streak on the floor is actually a bump. It’s not a very big bump, but it is higher than the rest of the floor. Very small bumps on a brake rotor can be “felt” in the brake pedal. Every time the bump comes around and slides between the pads, the pedal moves up against your foot. A bump of .0005″ (1/2 of a thousandth of an inch, which is six times smaller than the thickness of a human hair) can be felt when braking.

The lumps can be created a few ways. One is to overheat the pad and then mush it into the rotor while nearly stopped. “Melting” brake pads will leave an even smear on the rotors if you’re moving, but if you’ve braked all the way down a steep hill, then jab the brakes when the car’s barely moving, you might leave a lump. Another way lumps can develop is a rotor that’s not running true bumping into the brake pad every time the high spot comes around. This can be caused by a rotor that was machined

Conclusion

That’s about it: genuine pads from the dealer, proper lubrication, and a rotor with a flat surface that’s running true. That’s what makes a good brake repair. It’s pretty simple, but not all that common. Using cheaper aftermarket pads if far more common than using factory pads. Sometimes cheaper pads are used by a shop to offer a more “competitive” price. Sometimes shops will charge genuine part prices for aftermarket parts so they can make more money. Sometimes clients are offered genuine pads but decline due to cost and insist on getting aftermarket pads. Regardless, now you know how we feel about it, and you can make an informed decision. Happy motoring (and braking!)