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The practice of most drivers is to wait until the vehicle itself makes it known that the brake system needs attention. This is often too late, from a cost perspective.
There are various ways in which the vehicle will advise you of the need for the brakes to be serviced. The first two are the easy ones, both of which are related to sensors, either mechanical or electronic sensors, providing advance warning of the need to service the system.
The mechanical sensors will normally provide a screeching sound which is caused by a specifically designed piece of metal finally touching the brake disc, after sufficient wear of the brake pads. The electronic warnings are usually in the form of a warning light on the dashboard, which is also activated after sufficient wear of the brake pads has occurred.
The non-sensor warnings of a brake system in need of urgent service are more brutal, the most common warning being the age-old ‘Metal to Metal’ noise, which sounds like a severe grinding of two surfaces together. The other warning is the one that comes too late for your safety and that is when the vehicle fails to stop when required, hopefully not causing an accident. Both of these warnings occur at a point where the costs are exponentially increased due to additional parts damage, like discs, drums, shoes, and even callipers at times.
The best practice for brake safety is to monitor first the kilometres travelled since the last brake inspection, and/or to note that the brakes should be inspected during a routine service. However, it is always a good idea to be aware of these safety critical (Life and Limb) components. Most RMI TDAFA accredited fitment centres will be able to inspect your brakes and if necessary perform the brake service required in order to keep you safe on the roads, with reputable parts sourced from an RMI MPEA (Motor Parts and Equipment Association) accredited dealer.
So far we have referred to the Brake System, so let’s look at the various parts of a brake system, in no particular order, which will emphasise the complexity of the system and show that a vehicle’s brakes are more than just brake pads:
- Brake Fluid (DOT 4, or DOT 5.1 Only and Not Hydraulic oil or fluid)
- Brake Pads
- Brake Discs
- Brake Callipers
- Brake Master cylinder
- Brake Hoses (not hydraulic hoses)
- Brake shoes (rear)
- Brake Drums (rear)
- Wheel Cylinders (rear)
A best-practice brake service will require a number of steps, more than just a quick change of brake pads.
The first step is to determine if the brake pads have worn down. The quickest way to check this is by inspecting the brake fluid under the bonnet, provided that no one has topped up the brake fluid. If the brake fluid level has dropped, it is a fair assumption to make that the brake pads either require replacement or are nearing replacement. This can be done by anyone.
Once it is established that a brake service is required, it must be understood that the Brake System is a whole system, in that all the components work together in a set manner. As such, the Master Cylinder must be able to transfer sufficient Brake Fluid pressure to the Brake Callipers and/or Wheel Cylinders for them to be able to actuate the brake pads and/or shoes against the discs or drums, which in turn will provide the energy transfer demanded to stop the vehicle safely.
This means the brake fluid must be in good condition to be able to provide adequate pressure at the temperatures for which it is designed to operate within. Where brake fluid has become dark in colour it is a fair assumption that the brake fluid requires a flush out and change. Most manufacturers of brake fluid will recommend a full change of brake fluid at least every 24 months if not sooner.
How long do brake pads last? This is a question often asked, and the only answer is that it depends on the driving style (speeds, braking, etc.), the usage of the vehicle, the road conditions where the vehicle is used, loads carried in or on the vehicle, and if the vehicle is used for towing of trailers or caravans. These are all factors contributing to varied rates of wear of the brake pads. So in a nutshell, there is no finite answer to the question.
When an RMI Fitment Centre performs a brake service there are a number items that require observation and evaluation during the work. This essentially requires some “Time”, and although we are all in a hurry, the servicing of a brake system should not be rushed – it is after all the most safety-critical part of a vehicle.
The callipers are intricate components which are made up of a body with a bleed nipple, sliding pins and their seals and dust covers, and finally a piston which has a pressure seal and a dust cover. Common conditions that occur with callipers that cause premature brake wear, brake fade and ultimately brake failure are manifested in the lack of attention to the service of the callipers. All the items mentioned need to be clean, free from restriction of easy movement and not worn or damaged in any way (especially the internal seals and dust covers). Where any interference with movement is noticed it is a clear indication that the calliper needs to be stripped and cleaned properly, using white spirits only. Interference would be indicated by the inability to push the piston backwards by using only one’s thumbs (provided the bleed nipple is open to waste). The use of clamps and tools to retract the pistons (unless it is a handbrake calliper, which requires another technique) is never advised.
Seals should always be replaced, and the piston and slide pins polished during a calliper service.
New brake pads should never be fitted to a brake system without either skimming the brake discs or replacing the brake discs. WHY? You ask. Skimming of the discs is not only to get a smooth surface but an essential part of the brake service process. The brake friction material (brake pad) needs to transfer into the brake disc across the entire portion of the bisc where the brake pad is forced against the disc (the brake path). This is known as “Bedding-In” of the brakes. For this to occur efficiently and completely, the disc surface needs to be clean and free of any other older bedded-in residual brake friction material (previous brake pads) to prevent the contamination of the new brake pads being fitted. There is no short-cut. It is either skim or replace, or else you will not get the best value for money from the new brake pads.
Let’s explore the brake fluid a little. This is a fluid which is known as a hygroscopic fluid, which means it easily absorbs water. Brake fluid is required to resist boiling (forming gas bubbles) up to certain levels of temperature. This allows the pressure to be maintained during braking when heat is generated. When the fluid absorbs water it negatively affects the Boiling Point of the brake fluid. A mere 3% of brake fluid will reduce the boiling point by 50%, which is patently dangerous. Under normal conditions brake fluid can absorb as much as 3% in a space of three years. Thus, for safety’s sake the recommendation is to change the brake fluid completely every two years for safety, and that means your safety.
Now you may say, OK the front brakes are serviced and sorted out, let’s go!!! But wait there’s more, to come.
Remember we said the system is a whole system. Now that we have dealt with the front brake system, we need to move our focus to the rear brakes. In the event the rear brakes are callipers, discs, and brake pads, the same applies as with the front brakes for cleaning and servicing, except in the case of Handbrake Callipers, which will require the use of a wind back tool to retract the piston into the calliper body.
If the rear brakes are drum brakes (currently most common) then the principle of cleaning everything and ensuring free and unrestricted movement also applies. The important issue with the rear brakes as part of the whole system is to ensure that the rear brakes are correctly adjusted.
The brake system is designed that most of the brake force is applied at the front of the vehicle, with a lesser portion at the rear. The vehicle requires a 100% brake force, which is applied through the front and the rear brakes and is split as an 80/20, 70/30 or 60/40 per cent ratio between the front and the rear. Where the rear brakes are not working or are incorrectly adjusted, then 100% of the braking is demanded at the front, which the system was not designed to provide. This causes high brake pad wear rates at the front, reduced braking efficiency, and can lead to brake failure for the vehicle.
So in conclusion, we need to accept that a brake service is more than just a quick job. It is a skilled process, requiring knowledge and experience. The process does takes time to perform completely and correctly. Brake system service is best not performed as a DIY function, unless all the parts and knowledge are on hand. Rather engage the services and expertise of an RMI accredited TDAFA fitment centre.