Be sure to check your calipers

It may not be the biggest part in the braking set up, but a corroded, broken, or cracked slide pin could well be affecting the braking power of your truck and it can be easy to overlook.

Australian brake manufacturer Bendix has issued a note to the industry about good brake servicing and the need to double-check caliper wear.

“On vehicles fitted with disc brakes, calipers play a crucial role within the braking system, using their hydraulic muscle to squeeze the brake pads against the rotors to safely bring the car, truck or motorbike to a standstill,” Bendix says.

“Despite their important function, brake calipers can sometimes be overlooked, only coming to the attention of the owner or service technician if they notice that their brakes aren’t performing as they should.

“Because of where calipers are located on the vehicle, they operate in extremely tough conditions being exposed to dirt, road grime, water and even mud – they must also endure high temperature variables. Given these demanding operating parameters, it makes sense that they should be closely inspected at the same time as brake pads and rotors are checked or replaced.”

Bendix advise technicians to pay particular attention to the wear on the brake pads, suggesting that uneven wear, from inner to outer, could be caused by a caliper problem.

“Calipers are made up of many components including a piston(s), seals, dust boots, locking bolts, slide pins and mounting brackets – several of these are moving parts which can make them susceptible to seizing or failure,” Bendix says.

“One of the first components to inspect if there’s an issue with a caliper, or as part of caliper servicing, are the slide pins. Even though there’s a protective rubber covering the slide pins they’re still exposed to brake dust build-up and corrosion, which will hinder the calipers from sliding properly.

“If the slide pins don’t move freely, they should be removed cleaned with a wire brush or sandpaper to get rid of any debris, grease and corrosion, and then a heat resistant lubricant should be applied before refitting.”

Another issue Bendix identified was that of sticking pistons.

“This can be caused by corrosion in the piston bore or the piston itself.

“If the piston sticks it may not apply enough pressure to the brake pads to safely bring the vehicle to a stop.

“Alternatively, if the piston sticks when retracted, it can cause brake drag and pull the vehicle to one side, while also leading to premature brake pad and rotor wear.

“Depending on the type of caliper, corrosion inside the piston bore can be cleaned or honed (cast iron calipers), allowing the piston to again move freely.

“Unfortunately, the same process can’t be used with aluminium calipers, as sanding will remove the protective anodised coating inside the bore, which ultimately will cause even more corrosion.

“If any corrosion is evident on the pistons themselves, these should be replaced.

“Steel pistons feature an anti-corrosive coating while aluminium variants have an anodised coating, if these coatings are abrasively cleaned, the coating will be compromised and the corrosion will return.”

Technicians are advised to check the synthetic rubber caliper piston seals and dust covers too – and replace them if they are broken.

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