When it comes to brakes, close enough isn’t good enough
If you’re buying slippers, toques or sweaters, a close fit is good enough. Some things in life are “one-size-fitsmost,” after all, and tend to work just fine even if they’re a bit too big, or a bit too small.
Other things in life require a very precise fit. Like batteries, light bulbs and charging cables, the brake rotors on your car or truck are built to a specific size and shape. Get these wrong, and they probably won’t work at all.
Dawn Mueller is a good friend, and a service advisor at a Canadian car dealership. Recently, she told me a story that nicely illustrates the importance of using proper parts, of the proper size, if you decide to do a brake job on your car or truck.
One of Mueller’s customers stopped in with a nearly-new crossover that was in some serious need of help not long after he’d attempted to do his own brake job. The twoyear-old compact vehicle arrived on a tow truck, and was dragged into the shop with a single rear wheel that was locked solid. This left a 20foot skid mark on the shop floor, complete with gouges from its recently-installed studded winter tires. The locked-up wheel was the result of the customer’s badlybotched brake job.
“He sourced his own parts from the internet, but selected the wrong rear brake rotor for the job,” Mueller said. “There are two rear brake rotors available for this model, and they’re extremely close in diameter to one another. With the naked eye, you’d hardly be able to tell the difference.”
A brake rotor is a preciselysized round metal disc that’s responsible for much of your vehicle’s ability to stop. The rotor spins in sync with the vehicle’s wheels, while the brake caliper, pads and other components float over it with minimal clearance. When you brake, the caliper squeezes the brake pads against that spinning rotor, generating the friction required to stop the car. Clearances in this system are very tight, and that’s why it’s extremely important for the installed brake rotor to be exactly the right size. There’s no room for error.
Mueller’s customer had ordered and installed a rotor
that was just slightly too large. “It was very close,” she said. “If he’d had ordered the parts from my counter, we’d have cross-checked against the VIN (vehicle information number) of his vehicle to make sure he had the right parts, the first time. Buying online, you’ve got to be careful, as you don’t always have an experienced professional double-checking that you’re getting the proper part.”
The real kicker in this situation is how closely-sized the two possible rotors are. Though the customer was able to physically fit this slightly-too-large rotor into
place, reinstalling nearby components would have been a frustrating and exhausting experience.
“A professional would have caught the problem immediately,” Mueller said. “Without years of experience working on brakes, this customer didn’t see an issue, and forcefully proceeded with the installation.”
After eventually finagling and fighting his rear brakes back together with (we assume) no shortage of struggle and swearing, the customer began driving the vehicle. Many parts had been forced into place and others over-tightened, causing deformation and damage. Not surprisingly, the rear brakes made some awful noises from the get-go, and didn’t last long before total failure caused the rear-wheel lockup situation that brought the machine into the shop.
The result? Bent and broken brackets aside, the replacement brake rotor was also destroyed – but not before it machined its way into the nearby caliper saddle, damaging that component too. The brake rotor then failed structurally, when a round fracture eventually broke it into two pieces.
“This is what happens when you don’t know what you’re doing, and become frustrated and angry, and wind up breaking things when you try to force them back together,” Mueller said.
“Thankfully, there was no accident and nobody was hurt. Brakes should be serviced and cared for in a specific way, by an experienced professional. In this case, the customer was trying to save a few dollars, but the repair bill to fix the damage he caused is presently at $2,000 and counting.”