Whether it’s everyday driving for work or pleasure, towing or hauling, or lapping your favorite road course, brakes should be the top priority when it comes to keeping you and your vehicle safe. For the inside track on keeping the brake system performing at its best, we turned to Mark Fowler, product specialist at Baer Brakes.

How You Know Brakes Need Attention

“Brakes are good at warning you of signs of trouble,” he begins. “They might start squealing or squeaking, even when not being applied, which is a sign of worn pads. If you hear grinding when you’re applying the brakes, that’s a good indication that something has happened to one or more of the pads or brake shoes. Clicking or rattling can indicate that an abutment clip or anti-rattle spring has broken, and it’s causing a brake pad to rattle. Diminished brake performance, changes in the brake pedal feel or travel, vibrations, pulling to one side, or a burning smell, are all further signs that the system needs attention.”

Happily, there are plenty of simple things a hobby mechanic can do to keep the brakes working effectively. Let’s look at some common brake-system maintenance tasks.

How to check for brake pad wear

Most OE brake pads come with wear indicators, a small metal tab or tag that makes contact with the rotor as the pads wear down.

“It will start to squeak or squeal, depending on the pad wear,” says Fowler. “If it’s in constant contact with the rotor, it quickly becomes annoying. But even before it gets to that, a regular visual check is always a good idea. If you have your tires and wheels off for any reason, just take a look down inside the caliper at the pad. The wear should be even – side-to-side on the caliper for the inner and outboard pad and left to right on the vehicle as well.”

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Usage and pad material will determine how long a set of pads lasts. Regular towing will create the potential for higher pad-wear, for example, while a high-ceramic-compound pad usually wears less rapidly than an aggressive, semi-metallic or metallic pad. Fowler adds that the pads on larger trucks and SUVs tend to wear more quickly than those in a car, both because of the increased vehicle mass, and because the OEMs usually deploy a more aggressive pad material to deal with that mass. Elsewhere, performance vehicles generally have a greater range of pad materials available.

When does a brake rotor need replacing?

Brake rotors, or discs, are one of the most visible elements of the brake system, but not all damage to a rotor will be visible: it might instead be something you feel when driving.

Imperfections and damage to the rotor surface comes in several forms. The first is ‘crazing’, which is caused by thermal stress and fatigue. It manifests in what look like hundreds of tiny cracks but are in fact microscopic changes in the rotor surface.

“Crazing is not uncommon, especially if you’re inducing a lot of heat into the rotor through towing, driving through the mountains, or on track,” says Fowler. “But it doesn’t usually affect the performance or longevity of the rotors, whereas a true crack in the rotor, would. With crazing, if you take your fingernail and rub it across the rotor surface, it usually won’t catch on one of the marks. However, a visible crack across the friction surface is usually a lot longer and wider than crazing, and you will be able to feel it with your fingernail. If it’s cracked, the rotor is on its way to failure and needs to be replaced.”

Another form of rotor damage is pulsation, often referred to misleadingly as ‘warped rotors.’ There can be two causes for this. One is a hot spot in the rotor, where the metallurgy has changed. The other occurs, for example, when you’re coming down the mountain range with heat in the brakes. At the stoplight at the bottom of the hill, you hold your foot on the brake pedal. In both scenarios, due to the high heat in the rotor, the brake pad imprints itself onto the rotor, depositing a thin layer of pad material that is just a little higher than the rest of the rotor surface.

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With continued driving, the deposition continues to build up over time. That creates a pulsation when braking – an uneven pedal feel as the rotor rotates – which leads the driver to believe that the rotor is warped, rather than just an uneven buildup of pad material.

“Sometimes it is possible to machine away the buildup by turning the rotors down, as long as you remain within the manufacturer specs,” he continues. “But if there is a hot spot in the rotor, the pad material will build up on that spot again over time. If you have machined the rotors and replaced the pads, but within 5,000 miles you start experiencing that pulsation again, that’s a good indication that the metallurgy of the rotor has changed, and you’ll need to replace the rotor.”

Shop Baer Big Claw and Big Claw HD rotors here.

Corrosion can also be a problem for steel brake rotors. If the vehicle has sat for an extended period in a moist environment, for example, and accumulated a lot of surface rust and pitting to the rotors, they will likely need at least machining, if not replacement. But if mild rust appears on the friction surface when the car has sat undriven for a couple of weeks after a storm, it will likely be removed when you hit the brakes for the first time.

“If you drive the car day to day but you’re seeing rust buildup on the rear rotors, that’s an indication that the rear brakes aren’t working at all, and that’s probably an issue that needs to be addressed,” cautions Fowler. “If it’s only on one side, it could be a caliper issue. If it’s on both sides, that could be something further up the line – a blockage from the master cylinder or in a line, for instance.”

Lubricating the brake-caliper slide pins

Particularly if you live in a cold climate, where winter salt and slush buildup can be an issue, it’s good practice to annually lubricate the brake caliper slide pins, so that the calipers continue to activate properly when required and corrosion does not set in. The issue may be exacerbated in EVs or hybrids that use regenerative braking to help slow the vehicle – rather relying on friction braking alone – as it leads to reduced brake use.

“If corrosion gets onto the slide pins, that can stop the caliper moving as designed,” he explains. “Most factory calipers are floating, allowing the caliper slides in and out on a fixed anchor bracket. If those slide pins and sliding surfaces get corroded enough to stop that happening, the result is uneven pad wear, with more wear to the inner pad. It can also affect the braking capabilities – the car might pull one way or the other.”

In less-aggressive climates, slide-pin cleaning and lubrication can usually be saved for when pad-replacement or any other form of brake maintenance is being performed.

Replace rotors and pads in pairs

“The front brakes usually wear out sooner than the rears,” Fowler continues. “If you’re replacing the brakes on one axle, you do not always need to do the whole car, but it’s common practice to replace left-and-right pairs of rotors and/or pads, together. Calipers do not necessarily need to be replaced in pairs, but changing brake rotors or pads together helps to keep the brake system more balanced. Brake pads are inexpensive for the most part, so just replace them in pairs.

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“It’s the same advice with rotors, it’s a good idea to replace both sides together, just so the thermal balance remains the same side-to-side. The rotor is a place for the caliper to clamp onto, but it is also the radiator for the braking system. The rotor’s main job is to take the heat that’s generated during the friction of stopping and dissipate it into the air. As brake rotors wear, the rotor – the radiator – becomes less effective, because you have less material to absorb the heat. That may not be an issue in day-to-day driving, but if you’re coming down a mountain, or towing, you’re potentially going to overheat one rotor quicker than the other. That in turn can cause brake-performance issues or cause the vehicle to pull to one side or the other, as the heat builds up differently in the two rotors.”

“One sign that the brake fluid is deteriorating is that the pedal might start to feel a little spongy or soft,” Fowler explains. “It might have a bit of a sinking feeling, or stopping distances may not be as good as they were. Then there is the appearance of the fluid itself, which can become dark, dirty, or sludgy looking. A brake warning light on the dashboard could be another trigger.

“When deciding when to change the brake fluid, always start with your manufacturer’s recommended interval and then adjust based on your usage,” he says. “As a general rule, brake fluid should be changed at least every two-to-three years. But several variables will influence that interval, including driving conditions, climate, the type of brake fluid, and how the vehicle is being used.”

The two major factors that cause brake fluid to deteriorate are moisture and heat. Brake fluid is hydroscopic, so it absorbs moisture over time. This reduces the fluid’s boiling point, making it less able to maintain hydraulic pressure – and therefore brake pressure – in hard or repeated use. The fluid is also more prone to absorbing moisture in hot, humid climates.

Fowler notes that DOT 4 and DOT 5.1 are both glycol-based brake fluids, but DOT 5.1 has a higher boiling point. So, while it will still absorb moisture and experience a performance deterioration over time, DOT 5.1 will take longer to deteriorate to a potentially dangerous level, having started from a higher base. Note that the presence of water in the fluid can also lead to corrosion inside the brake system.

Meanwhile, extensive towing, mountain driving, stop-and-go, or track use – anything that generates a lot of heat – will also hasten the deterioration in brake fluid. Fleet users such as taxis, ride shares, and delivery drivers, for example, might all consider a shorter fluid-swap interval. Track-day drivers putting extreme heat cycles through the brake system might even change (or flush – it’s the same thing) the fluid daily.

Old brake fluid should always be disposed of through the proper channels and never reused. Fowler says to be wary, too, of a bottle of fluid – opened or even sealed – that’s been sitting on the garage shelf for a few years. Just like the fluid inside the master cylinder on the car, it’s been absorbing moisture all that time, and the chances are, its boiling point has been reduced.

Drum brake maintenance

Brake drums, if fitted, are the final area of the brake system that may require maintenance. A brake drum provides a place for the shoes to create friction and absorbs and dissipates heat: it does the same job as a rotor, just not as effectively. Most front brake drums on older vehicles are finned to help with heat dissipation. Fowler’s advice is the same as for rotors and pads: replace them in pairs.

“You very seldom see cracking on brake drums, but you can experience the same pulsation that arises with a rotor. On a brake drum, it’s usually caused by applying the parking brake when the brake system is hot. Over time, that can cause the brake drum to distort away from a perfect circle, so you feel that pulsation in the pedal. Again, turning the brake drum, so long as the diameter remains within OE specifications, is usually all you need to fix that.”