Next to checking your oil and tires, one of the most vital maintenance tasks is looking after your brakes. If brake pads wear too much, not only does stopping safely become more difficult, you risk damaging the rotors themselves. But even with modern brake technology, sometimes the pads just don’t wear evenly. However, sometimes that’s because of modern safety technology.
Recently, I was helping my parents rotate their crossover’s tires when we took a look at their brake pads. They’d been making more noise than usual, but initially, nothing seemed amiss. But looking more closely, we saw that the rear brake pads were worn almost to nothing. Luckily, they had some replacement pads on hand.
Your brake pads, electronic stability control, and traction control
The brake pads had roughly 40,000 miles on them, which Bridgestone reports isn’t an unusually low mileage. However, although the rear ones were gone, the front pads were still usable. Usually, it’s the front ones that wear faster, NAPA explains. That’s because braking shifts the car’s weight forward, which means the front rotors need to be stronger, NAPA explains.
But there is a reason why rear brake pads can wear faster than expected: traction control and electronic stability control. Besides (for some cars) the tire-pressure monitoring system, your ABS is linked to the ESC and traction control, Motor Trend reports.
The two systems are linked, receiving data from various sensors, including ones in your braking system. Traction control manages wheelspin, the Chicago Tribune explains, while the electronic stability control governs handling. If the car thinks it’s sliding out of control, it automatically applies specific brakes to bring itself back in line.
Because of this, ESC also sharpens a car’s handling, Car and Driver reports. And that’s where the rear brake pads come in. Braking the rear wheels prevents understeer, SaferCar.gov explains and tightens-up turns. It’s not exactly a torque-vectoring or limited-slip differential, Car and Driver reports, but the basic principles are the same. Plus, rear-wheel braking mitigates some of the forward diving that normally occurs, Bendix and PistonHeads forum users report.
On top of that, because rear brake pads typically deal with less force than the front ones, they’re usually thinner. Combined with the electronic stability control and traction control, and you have accelerated rear brake pad wear.
Uneven brake pad wear isn’t always normal
However, there are situations where brake pad wear is abnormal, Firestone reports. Specifically, if the pads on one wheel or one side are especially worn. That points to an issue with the braking system itself.
Some of this uneven wearing maybe the rotor’s fault, DriveTribe explains. If the rotor’s surface isn’t even, it causes the pads to wear unevenly too. Brake pedal vibration, excessive noise, and extensive rotor scoring all point to an uneven or warped rotor, YourMechanic reports.
Other potential problems can be pinpointed by looking at the worn brake pads themselves, KnowYourParts reports. If the inner pad is more worn, it means the caliper piston isn’t backing off properly, keeping the pad in contact with the rotor. A worn outer pad means it’s not backing out with the caliper after releasing the pedal, YourMechanic explains. And if the pad material tapers, the pad is misaligned, or the caliper’s components are seizing.
How to repair these issues
If the rotor itself is the issue, the easiest solution is to resurface it, machining the surface back to a uniform thickness. But you can only do that so many times before the rotor becomes too thin to be effective. At that point, replacement is the only option.
If it’s an issue with the brake caliper itself, it may require replacing the entire caliper or a few key components, such as the rubber piston seal or slide pin. It’s also possible your brake lines may be causing the problem—check to make sure none of the hoses are leaking.
If it’s a misaligned brake pad, make sure to replace the pads on both sides of the axle and install new retaining hardware. Otherwise, the uneven wear will continue, or even worsen.
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