Best practice tips for commercial vehicle brake pad replacement
Replacing brake pads on any vehicle is a demanding and safety critical task to ensure the safety of the driver and other road users. While all technicians are familiar with the procedure for changing brakes on a commercial vehicle (CV), it is often the simplest tasks such as cleaning that are overlooked due to time pressures.
It is these smaller parts of the job that can sometimes have the biggest impact on the vehicle’s braking performance. Brake friction expert TMD Friction – the manufacturer of premium CV brake brand, Textar – has compiled a list of best practice tips to assist any CV technician in efficiently replacing brake pads and discs.
Correct equipment
Prior to starting any work, it is important to ensure the correct safety equipment is in place and any special instructions set out by the brake system’s manufacturer are followed. No brake replacement procedure is completely dust free, and for that reason, it is key that all precautions are taken. Always wear protective clothing (PPE) when working on the brake system or vehicle and only work on vehicles on a safe lift, not a jack.
The highest risk of dust contamination occurs when removing the brake pads and discs and cleaning the associated parts in preparation for the new brakes. Cleaning these products in a chemical wash facility is an efficient way to remove most of the dust. Alternatively, a suitable brake cleaner such as Textar Formula XT can be as effective and help to reduce airborne dust.
Before starting work
The first step taken should be to confirm the vehicle’s wheels are chocked. It is also vital to release the service and parking brake, as well as any other temporary hold brakes. Verify that the supply air pressure of the braking system is above 6.5 bar and, if possible, connect an external air supply to maintain system pressure.
Important! Always refer to vehicle manufacturer’s guidelines and only work on the brake system if you are fully trained to do so. Next, remove the wheel using the appropriate tools.
Brake pad removal
Once the wheel has been removed, the caliper’s position will be in view. The orientation of the caliper will always differ, depending on the axle or vehicle requirements.
Start by removing the spring clip and washer, then lower the pad retainer and detach the pin. Slide out and remove the pad retainer before disconnecting any wear sensor components, if necessary. Take care that the pads do not fall out of the caliper when removing the retainer.
After disconnecting, pull the adjuster cap using the tab, ensuring the shear adaptor remains in place. Do not use tools to remove the adjuster cap, as this may damage the sealing elements.
Caution! Always use a suitable wrench to carefully de-adjust the brake. Do not use air or power tools as this can cause damage to components. Also be aware that non-genuine adaptors may not shear correctly, potentially causing expensive and unnecessary damage. The shear adaptor is designed to fail if there is a problem during readjustment, preventing damage to the internal caliper components.
Fully wind back the tappet and boot assemblies by rotating the adjuster and using the shear adaptor in an anticlockwise direction. A loud noise should be heard when conducting this procedure. You can then begin to remove the outer brake by sliding the caliper towards you, and then remove the inner brake by sliding the caliper away from you.
Replacing the brake pads
Brake pads should only be replaced in axle sets. Prior to any fitment, the carrier and its pad support need to be cleaned and examined to ensure the pads fit correctly, both for initial and continual fitment. This can be done using a wire brush or caliper file, but be careful not damage to the brake caliper during the process.
Depending on the application and duty of the brakes, a suitable lubricant such as Ceratec should be used for the carrier abutments and contact areas. When applying the lubricant, avoid any contamination of the brake pad surfaces. Ensure the areas on the carrier are clean and free from corrosion, and take care not to use too much lubrication as this will collect wear debris and road ingress during the use of the vehicle.
Before inserting the freshly lubricated brake pads, check that all tappets are fully wound back by rotating the shear adaptor in an anticlockwise direction. Then, insert the inboard pad by pushing the caliper away from you. When in position, pull the caliper towards you to place the outboard pad.
Once fitted, wind the adjuster with the shear adaptor in a clockwise direction until contact is made with the pads and brake disc, before turning the adjuster in an anticlockwise motion for three clicks.
Completing the replacement
After refitting the new pads, check the running clearance in accordance with the brake system manufacturer’s service manual. Use a feeler gauge for this measurement. Incorrect clearance can lead to brake failure if too great or overheating if too small, potentially damaging the brakes.
Once the measurements comply with the manufacturer’s specifications, refit the adjuster cap and pad retainer, then replace the spring clip. Finally, refit the wheels using the appropriate tools and refer to the manufacturer’s recommendations for the correct torque settings.