Braking specialists, TMD Friction, via its Textar brand, has issued its best practice advice and handy tips designed to help technicians with the efficient replacement of commercial vehicle brake pads to ensure optimal performance and safety for fleet operators.
Textar recognises that in any vehicle, changing brake pads is a strenuous activity as the technician has to ensure the safety of the driver is never compromised. And while all technicians will know how to change brakes, it is often the simplest things, such as cleaning, which can be overlooked due to time constraints.
Scott Irwin, MIMI, head of technical training at TMD Friction IAM sets out a list of helpful tips on best practice when carrying out brake pad replacements on commercial vehicles.
Prior to starting any work, it’s important to ensure the correct safety equipment is in place and that any special instructions by the brake systems manufacturer are followed. No brake pad replacement is going to be dust free, and for that reason, it’s key that all precautions are taken.
As most trucks are worked on over a pit, Textar advises technicians to always wear PPE when carrying out procedures on the brake system and to only work on vehicles in a safe manner and to use the right lifting equipment such as a beam jack.
The highest risk of dust contamination is when the brake pads are being removed and the associated parts are being cleaned in preparation for the new brakes being fitted. Cleaning these products with brake cleaner, such as Textar Brake Cleaner Formula XT, is a must to reduce the dust particles given off from the parts.
Before starting work
The first job anyone should undertake is to confirm if the vehicle’s wheels are chocked. It’s also vital the service and parking brake, as well as any other temporary hold brakes, are released. Make sure the supply air pressure of the braking system is >6.5 bar, and where possible, connect an external air supply to ensure system pressures are maintained.
The brand also recommends to always refer to vehicle manufacturer’s guidelines and only work on the brake system if you’re fully trained to do so and has the correct tools to carryout out the job.
Beginning of 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 an axle or vehicle requirements.
To start the process, Textar explains that technicians should begin by removing the spring clip and washer before lowering the pad retainer and detaching the pin. Then, they should slide out and remove the pad retainer, before disconnecting any wear sensor components as necessary. When removing the retainer, it’s important the pads do not fall out from the caliper.
After this has been disconnected, pull the adjuster cap using the tab, whilst ensuring the shear adaptor stays in place. Tools must not be used during the removal of the adjuster cap, as this may cause damage to the sealing elements.
It’s important to note that the shear adaptor is exactly that, and in the event of a problem during readjustment, the adaptor will fail, ensuring the internal caliper components are not damaged.
There are spurious non-genuine adaptors available that may not shear, which in turn, could potentially cause expensive and unnecessary damage.
Next, Textar explains that the technician should fully wind back the tappet and boot assemblies by rotating the adjuster and using the shear adaptor in an anti-clockwise direction. A loud noise should be heard when conducting this procedure. Finally, the technician needs to remove the outer brake by sliding the caliper towards themselves, and then remove the inner brake by sliding the caliper away from themselves.
Replacing the brake pad
Brake pads should only be replaced in axle sets. Prior to any fitment, Textar advises that the carrier and its pad supports 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, caliper file, but caution should be taken to ensure no damage to the brake pads during the process.
Special instructions by the brake systems manufacturer should be followed. Depending on the application and duty of the brakes, a suitable lubricant for the carrier abutments and contact areas should be used – Some caliper manufactures might not recommend using grease. But Textar recommends using Textar Ceratec to allow the pads to move freely in the caliper; it’s also vital to avoid any potential contamination of the bake pad surfaces with any grease.
When lubricating, 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.
Before inserting the freshly lubricated pads, it’s important to ensure all tappets are fully wound back by rotating the shear adaptor in an anti-clockwise direction. Then, insert the inboard pad by pushing the caliper away from you, and once 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 anti-clockwise motion by three clicks.
Completing the replacement
Once the new pads have been refitted, the running clearance should be checked in compliance with the brake systems manufacturer’s service manual. It is important that this measurement is taken using a feeler gauge and is between 0.6-1.2mm, as anything above or below may cause problems. If the clearance is too great, there’s potential risk of brake failure, and if it’s too small, there’s a chance of overheating, which in turn, will damage the brakes.
If the gap is larger than 1.2mm, the adjuster must be checked by referring to the manufacturer service manual. Once the measurements are achieved, the adjuster cap and pad retainer can be refitted, before replacing the spring clip.
Finally, refit the wheels using the correct tools and while still referring to the manufacturer’s recommendations, ensure the required torque settings are adhered to.