This Tech Tip came from Bendix Brakes about Brake Dust, the logic is sound, but I wish there was a test to determine the health of the caliper seal besides observing the symptoms…
Caliper Retraction Critical Component
Troy, Mich., July 23, 2008 – As technicians service brake systems on more vehicles with alloy wheels, the Bendix® Brakes Answerman team recommends paying special attention to the brake calipers.
“More and more vehicles leave the factory with alloy wheels and while they greatly enhance the appearance of a vehicle, they also generate more complaints from consumers due to brake dust,” said Jay Buckley, Honeywell CPG technical training manager and Bendix® Brakes Answerman. “A number of factors go into reducing the amount of brake dust that ends up on a vehicle’s wheels – like the use of ceramic brake pads, for instance – but a properly functioning caliper also plays a key role in preventing the unsightly grime on today’s wheels.”
So beyond removing all rust and corrosion from a caliper’s sliding area, inspecting the caliper for proper retraction is important, especially on old calipers that haven’t been changed. Even though the piston gets pushed in and everything seems to be working normally, on older calipers, retraction can take longer than it should.
“The square cut seal inside the caliper does more than keep fluid inside. It actually winds up like a rubber band when the brakes are applied so it acts as a spring, retracting the caliper pistons and getting the pads back off the rotor,” said Buckley. “Like any spring that expands and retracts thousands of times, it will eventually become fatigued.”
It may then do a poor job of retracting the pads back off the rotor. This slow retraction allows the pads to remain in contact with the rotor longer than needed, resulting in more brake dust generation and premature brake wear.
“If you are servicing a high mileage vehicle that has chronic ‘brake dust’ and it has not had regular brake fluid flushes, it may be time for a pair of fresh calipers.”
The Bendix® brand has two caliper options for technicians to choose from, all of which include the necessary hardware and components for quick installation, as well as pre-lubed and pre-assembled bushings and guide bolts if the OE design calls for it.
• Bendix® Loaded Calipers are assembled using genuine Bendix® premium disc brake pads to provide quality and performance that professional technicians have come to expect.
• Bendix® Select Loaded Calipers allow technicians to select which Bendix brand friction they want included. All calipers are individually wrapped in vapor corrosion inhibitor paper for maximum shelf life.