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Other things being equal, disc brakes have a much longer service life than drums. But contrary to some operators' beliefs, disc brakes are not 'fit-and-forget'.
Don Coffrey, technical manager at Ferodo, reports that some operators are switching back to drum brakes, citing poor performance from their disc brakes. "It is a backward step," he warns. "Only disc brakes can give consistent braking performance time after time, regardless of the temperature they reach.
"Disc brakes will give long service life, but you do need to check them. If the gaiters split and water gets into the caliper it will corrode. it's not enough just to change the pads: the calipers and discs need checking too."
Ferocto's 4569 friction material was developed for trailer disc brake pads; specifically for operatons such as trunking where the brakes rarely reach normal operation temperatures of 80-250°C.
"On some trunking operations there's very little actual braking and the pads remain cool," says Coffrey "That's good for life, but means that debris collects on the surface of the pad and doesn't get burnt off so the brakes lose efficiency"
Cool brake pads are often the culprit when trailers fwi their annual tests, he warns: "Operators are baffled because they do a brake service, change the pads, and then the trailer fails the braking performance test. That's because the pads are not at the normal operating temperature. All it takes is a few applications of the brake."
if brake temperature passes the 400"C mark the bond between the friction material and its backplate can break down, and the pad will fail. Ferodo avoids this by inserting an expanded mesh layer between the backplate and friction material. The material merges with the mesh during moulding so it wit not come loose.
High temperatures can also cause friction material to crack close to the centre line—even pads that have machined grooves might crack at vital stress points. The Premier pad incorporates a moulded V-Groove that is said to virtually eliminate the risk of cracking in this critical area,