Caliper servicing – is it necessary?

Most drivers accept that brake pads, brake shoes, disc brake rotors and brake drums are wear and tear items that will need periodic replacing, but what about brake calipers?

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.

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.

Savvy technicians may even be able to identify poorly performing calipers by inspecting the brake pads. Uneven wear (inner to outer) can potentially be caused by a caliper problem, as can uneven wear across the pad face.

What can go wrong with calipers?

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.

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 such as Bendix Ceramasil should be applied before refitting.

Sticking pistons can also lead to problems in calipers. 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.

Other potential wear items are the synthetic rubber caliper piston seals and dust covers. While they provide a good level of protection, they are unlikely to last the life of the vehicle, becoming hard and brittle over time and after long-term exposure to heat. Once brittle, the seals and dust covers will crack, letting in debris and moisture while also losing ability to hold pressure in the case of the seal, which could result in a brake fluid leak.

Given the potential problems that can arise within brake calipers, it pays to inspect them during vehicle servicing – this provides the opportunity to address any maintenance concerns before bigger issues occur.

For further information:

For more information free call the Bendix Brake Advice Centre on 1800 819 666 or +61 3 5327 0211 from overseas (8am-5pm Monday to Friday EST), e-mail us at: brakeadvicecentre@bendix.com.au or visit our website www.bendix.com.au