09/07/2001
When it comes to vehicle safety, few components are as critical as your braking system. Over time, brake pads and calipers can accumulate dirt, grime, and fluid residue, compromising their efficiency and potentially leading to costly damage. Regular cleaning and maintenance aren't just about aesthetics; they're about ensuring your vehicle performs reliably when you need it most. This guide will walk you through the essential steps to clean and maintain your brake pads and calipers, helping you achieve optimal stopping power and extend the life of your braking components.
The Unsung Heroes: Cleaning Your Brake Pads
Your brake pads are constantly at work, converting kinetic energy into thermal energy to slow your vehicle. During this process, they can accumulate a surprising amount of dust, dirt, and even fluid deposits from normal wear and tear or leaks. Ignoring these contaminants can lead to reduced braking efficiency, uneven wear, and even noise. A simple visual inspection is often all it takes to determine if your pads are in need of a clean. Look for visible dirt build-up or any signs of fluid contamination on the pad surface.
Should you spot any such issues, cleaning your brake pads is a relatively straightforward process, primarily involving a specialised spray. A dedicated brake cleaner spray is highly effective at dissolving and flushing away anything that might be impeding your brakes' performance. When using these sprays, it's crucial to ensure that the removed grime and fluid have somewhere to go. Always place a pan or tray directly beneath the brake assembly to capture all the gunk that will run off. Remember to consult local regulations regarding the disposal of such waste, as brake fluids and contaminants can be hazardous to the environment.
While the cleaning spray does most of the heavy lifting, a soft brush can be used to gently agitate stubborn areas if necessary, ensuring all surfaces are thoroughly cleaned without causing damage to the friction material. This simple step can prevent premature wear and maintain consistent braking performance, contributing significantly to your driving safety.
Beyond the Pad: The Caliper's Crucial Role
The brake caliper is the unsung hero of your braking system, housing the pistons that press the brake pads against the discs. Its proper function is paramount for effective braking. Many vehicle owners mistakenly believe that the brake pad wear warning lamp is a licence to ignore the condition of their pads until it illuminates. However, this warning is typically triggered only when the friction material has worn down to a critical 3mm thickness. At this point, there's a significant risk of damage to the brake discs, especially if pad replacement is deferred until the next service.
A more serious concern arises from the severely reduced heat-absorbing properties of such thin pads. With minimal friction material left, heat is rapidly transferred through the steel backing plate and directly into the caliper piston. This intense heat can severely damage the caliper's seals and potentially boil contaminated brake fluid, leading to a dangerous loss of braking ability. Therefore, regular inspection and maintenance of the calipers, alongside the pads, are vital for both safety and the longevity of your entire braking system.
Disassembly for a Deep Clean
To thoroughly clean your brake calipers and the areas where the pads slide, careful disassembly is required. This process, while manageable for the competent DIY enthusiast, requires attention to detail. Here’s a step-by-step guide:
- Unplug the Warning Light Connector: Begin by locating and unplugging the brake pad warning light connector, usually found on the inside of the wheel arch. This prevents damage to the sensor during removal.
- Release Grommets: Next, release the grommets for the pad sensor cable and the brake hose from their bracket on the suspension strut. These can often be very tight, so a small amount of WD-40 or a similar penetrating oil can greatly assist in their removal. Apply sparingly and ensure no overspray reaches the brake components.
- Remove the Flat Spring: A long, flat spring holds the caliper in alignment with the pads. To remove it, insert a large screwdriver between the spring and the centre portion of the disc. Gently lever the screwdriver to compress the spring until the small ‘ears’ at its inner ends are clear of the lipped holes in the caliper. Once clear, the ends of the spring can be pulled free of the caliper bracket, allowing the spring to be removed entirely.
- Access Caliper Mounting Pillars: Lever out the small caps that cover the socket-headed pillars on which the calipers are mounted. These pillars are crucial for the caliper's sliding action.
- Undo Mounting Pillars: Use a 7mm hexagon key (an invaluable tool, especially when part of a socket set) to undo the caliper mounting pillars. If they haven't been removed before, they might be quite stiff, so apply steady, firm pressure.
- Caliper Removal Challenges: It's at this stage, particularly on older vehicles with worn discs, that many owners encounter difficulty removing the caliper. This is typically because the outer edges of the pads become trapped under the lip that forms at the edge of the brake disc due to wear. Additionally, the inner pad might be rigidly attached to the caliper piston by a spring clip. The solution is to use a large screwdriver to carefully lever the pads apart. This action will push the inner pad away from the caliper piston and free it from underneath the disc's lip, allowing the caliper to be removed.
- Dealing with Corrosion: In extreme cases, especially in areas prone to salt corrosion, the steel backing of the pads may have rusted firmly to the caliper and its carrier. Gentle, careful levering should free the components without causing damage. Patience is key here to avoid undue force.
Precision Cleaning and Lubrication
Once the caliper and pads are successfully removed, the real cleaning work begins. Pay close attention to the areas of the pads and the caliper carrier upon which the pads slide. These surfaces must be meticulously cleaned to ensure the pads can move freely and without obstruction. Use a sharp screwdriver or a small file to scrape away any accumulated rust, dirt, or old grease until the pads achieve a comfortable sliding fit.
When installing new pads, it's a good practise to check their fit before final installation. If they are too tight, carefully file them down slightly, but exercise extreme caution not to remove too much metal. Excessive material removal will result in the pads being too loose, leading to an incurable rattling noise and potentially uneven braking.
It is paramount that the pads can slide freely. If they cannot, they will not be pushed back by the inevitable slight run-out of the brake disc or the natural compression of the piston seal. This seemingly minor issue is responsible for more wear on brake pads and discs than thousands of miles of normal operation. Furthermore, it will also lead to a slight reduction in your vehicle's fuel consumption due to constant, albeit minor, drag.
Before reassembly, lubrication is key. Do not be afraid to use an anti-seize grease, such as Copa-Slip, on threads and especially on the areas where the pads slide. However, it's crucial not to overdo it; a thin, even coating will suffice. Ensure that the working surfaces of the discs and pads remain completely clean and free from any grease. The best way to achieve this is by using a dedicated brake cleaner on a paper towel and maintaining clean hands throughout the process.
Additionally, extract the mounting pillars from the caliper. Lightly coat these pillars with silicone grease. This ensures that the caliper can slide freely on them, which is essential for consistent braking performance and even pad wear.
Reassembly and the Crucial Bedding-In Process
With your components cleaned and prepared, it's time for reassembly. This stage involves careful attention to detail to ensure everything functions correctly and safely.
Before fitting new pads, the caliper pistons must be retracted to accommodate their increased thickness. While a special tool is available from automotive retailers like Halfords for under £20, a large G-clamp and a small piece of plywood can serve as an effective alternative. Ensure that the clamp acts squarely to the piston to avoid damage. Slowly force the piston back into the caliper, constantly monitoring the fluid level in the brake fluid reservoir. If the level approaches the top, siphon out some fluid to prevent overflow.
Contrary to a common myth, the warning light contact can usually be easily removed from the old pad and reused with its replacement. Using a pair of pliers, gently squeeze the 'ears' of the sensor clip onto the cable and pull the sensor out of the pad in a radial direction. When replacing it, note that the sensor will only fit into the pad if it's in its correct orientation.
Now, fit the inner pad to the caliper piston and place the outer pad in the caliper carrier. Carefully slide the entire caliper/pad assembly over the brake disc and into its correct position. You may find that the caliper needs to be tilted outwards at its base to align the mounting pillars with their respective threads. Once aligned, fit the flat spring, reconnect the pad sensor cable, and insert the supporting grommets back into their bracket on the suspension strut. Your brake assembly is now complete.
Brake Pedal Firming and Bedding-In
With your brakes reassembled, the pads must be moved outwards against the discs. If your vehicle has accumulated high mileage, the master cylinders may have developed ridges at the ends of their usual travel. Pressing the pedal beyond this point could potentially damage the piston seal lips. Therefore, the brake pedal should be slowly depressed in short, gentle movements until it becomes firm. This firmness is a clear indication that the pads are now properly pressed against the discs.
The final crucial step, especially after fitting new pads or discs, is the bedding-in process. On the road, test your brakes progressively, starting from low speeds and gradually increasing. Crucially, avoid any hard or emergency braking during this initial period. While professional racers bed in their pads with aggressive braking, their pads are made from a much harder compound than those used in road cars. For a road car, light initial use of the brakes for approximately 300 miles will yield significant long-term benefits: longer pad life, improved performance, and freedom from annoying noise and vibration.
It's highly unusual for all associated brake components to be so precisely manufactured that new pads align perfectly with the discs from the outset. Therefore, a period of bedding-in is absolutely necessary to allow the pad material to conform to the disc surface, creating an optimal contact patch.
Addressing the "Loss of Bite" Myth
After the bedding-in period, or sometimes after a few weeks of normal commuting, many owners report that their brakes seem to have lost their initial "bite." Often, they are mistakenly told this is due to their pads becoming 'glazed' and that replacement is the only solution. This is largely a myth. If well-maintained and sensibly used, you should expect a lifespan of at least 30,000 miles from front pads and potentially double that from rear pads.
The true reason for this perceived loss of response lies in the fundamental way our brakes operate. For optimal performance, a thin layer of friction material needs to be intimately bonded to the surface of the brake disc. This bonding process requires a significant amount of heat. During periods of light braking (common in daily commuting), this crucial friction layer can be worn away. To regenerate it and restore full performance, this layer must be periodically replaced.
This means engaging in firm—but not excessively heavy—braking efforts, gradually increasing the duration of these applications until the brakes become genuinely hot. Crucially, allow adequate time between braking cycles for cooling. For instance, braking from motorway speeds down to 30 mph is generally inadvisable for this purpose; a long, gradual downhill stretch is far preferable. You will then find that your brakes are wonderful again, with their original responsiveness restored. Incorporating a decent level of firm braking into your weekly driving routine, and certainly before an MoT test, is a wise practise to maintain optimal brake performance.
Choosing the Right Pads
While the primary focus of this guide is on cleaning and maintenance, selecting appropriate brake pads can also impact the longevity and cleanliness of your braking system. Many owners have a preference for "Genuine BMW" pads, though they are often no better than other popular makes and can generate a considerable amount of brake dust. Pagid Fast Road pads are another example known for high dust production.
Unless you are a regular track day enthusiast, it's generally best to avoid the temptation to buy "competition" pads for road use. These pads seldom provide their full potential without being thoroughly warmed up, a condition rarely achieved during typical road driving. Few of us use our brakes hard enough, or for long enough periods, to make such pads effective, unless we frequently tow a heavy, un-braked trailer.
The best advice for selecting pads is to honestly assess your driving style and choose accordingly. For instance, EBC Greenstuff (road-grade) pads are often favoured for their performance in all conditions and their low dust generation, making wheels easier to clean with just a sponge and car shampoo. They also boast excellent wear characteristics, with some users reporting over 50,000 miles of life. For those with more extreme requirements, EBC Yellowstuff pads are reported to perform well when cold, even better when hot, and also maintain a low dust characteristic.
Brake Pad Comparison
| Pad Type | Dust Generation | Road Performance | Notes |
|---|---|---|---|
| Genuine BMW | High | Standard Road Use | Often comparable to aftermarket options. |
| Pagid Fast Road | High | Aggressive Road Use | Designed for spirited driving, higher dust. |
| EBC Greenstuff | Low | Excellent All Conditions | Good wear life, easy wheel cleaning. |
| EBC Yellowstuff | Low | Good Cold, Better Hot | Suited for more demanding use, low dust. |
Frequently Asked Questions (FAQs)
Q: How often should I clean my brake pads?
A: You should inspect your brake pads regularly for dirt and fluid build-up. If you observe any contamination, it's advisable to clean them using a dedicated brake cleaner spray. This helps maintain optimal performance and prevents premature wear.
Q: What happens if my brake pads don't slide freely?
A: If brake pads cannot slide freely, they won't fully retract from the disc when the brake pedal is released. This leads to continuous, albeit slight, contact, causing increased wear on both pads and discs, and can also slightly reduce your vehicle's fuel efficiency due to constant drag.
Q: What does the brake pad wear warning lamp indicate?
A: The warning lamp typically illuminates when the friction material on your brake pads has worn down to approximately 3mm. At this point, there's an increased risk of damage to your brake discs, and the pads' ability to absorb heat is significantly reduced, potentially leading to caliper damage or fluid issues.
Q: My brakes feel like they've lost their "bite" after a while. Are they glazed?
A: It's a common misconception that pads become "glazed" and need replacement. Often, this loss of "bite" is due to the thin layer of friction material on the disc wearing away during light braking. To restore performance, you need to re-establish this layer by performing a series of firm (but not heavy) braking efforts, allowing the brakes to get hot and then cool down. This process re-bonds the friction material to the disc surface.
Q: How long do brake pads typically last?
A: With proper maintenance and sensible driving, front brake pads can last at least 30,000 miles, and rear pads can last double that. Lifespan can vary significantly based on driving style, vehicle type, and environmental conditions.
Conclusion
Maintaining your vehicle's braking system is non-negotiable for road safety. By regularly inspecting and cleaning your brake pads and calipers, understanding the importance of proper disassembly and lubrication, and correctly performing the bedding-in process, you can ensure your brakes remain responsive and efficient. This proactive approach not only keeps you safer on the road but also contributes to the longevity of your braking components, saving you money in the long run. Drive safely, and make brake maintenance a regular part of your vehicle care routine.
If you want to read more articles similar to Brake Care: Keeping Your Stops Sharp and Safe, you can visit the Brakes category.