Dear Ask a Mechanic,
We recently took our 2015 Hyundai Tucson to the garage to have our summer tires replaced. During the process, we were informed that we had to have new brakes for all four wheels. My husband was told that one of the rear calipers had seized up and the front pads were also seized up and worn. I don’t understand how our car was able to brake properly when most of its brakes were stuck. Did we lie? Why did they insist on replacing both rear calipers instead of the bad one?
Tire changing seasons, spring and fall, are also busy times for brake work. Removing the wheels exposes the brakes, making them easier to inspect. And just like a Cracker Jack box, there can be a surprise inside.
Brake corrosion is common. The wear surfaces of disc brake rotors and their components are exposed to the air and the elements, even though they are partially shielded by the wheels and vehicle body. It’s not just due to riding in wet conditions either. The same moisture in the air that causes condensation or frost on your vehicle’s windows has a similar effect on metal brake parts. Even for those who park indoors, the corrosive effects of winter road salt and brine come into play.
Normally, if all else is good, regular use of the line will tend to remove this thin layer of corrosion from the wear surfaces quickly. But if the rust penetrates a little deeper into the surface of the rotor, the reverse happens. Swollen or pitted metal wears down the pad material, making the problem worse and possibly causing brake pulsation or noise. Working from home and other pandemic-related reductions in driving seem to have made this problem more prevalent.
Even partially seized brakes can continue to work to some extent. With power assist and hydraulic brakes, the pressures generated at the calipers can potentially bend the brake pad backing plates and caliper pins enough to apply some force. Under light to moderate braking, you may not notice the loss in performance. (Once applied, bonded pads may not fully release and may slip, resulting in uneven or excessively premature pad wear.)
As to why calipers are replaced in pairs, this is standard industry practice. Apparently, this preserves the balance of the hydraulic system. And, like changing both wiper blades when one starts to get dirty, it also reduces the likelihood that the other caliper, having experienced the same lifespan, could soon fail and damage the new parts. brake.