10 MIN TECH
This month we get to grips with the brake pad options available, and stop to see what they’re all about
Quick-fire questions and answers all about brake pads.
WHAT IS A BRAKE PAD AND HOW DOES IT WORK TO SLOW THE CAR DOWN?
During braking, force applied to the pedal is converted to a hydraulic pressure in the master cylinder. This brake fluid pressure is instantaneously transferred, via the brake lines, to the brake callipers. The increase in pressure causes the calliper pistons to extend, clamping the brake pad against the disc, which serves to convert the vehicle’s kinetic energy into thermal energy via friction.
The actual job of the brake pad is to generate a consistent level of friction against the disc across a wide range of temperatures. It also must maintain performance in the wet, have acceptable levels of wear, not produce too much dust and (preferably) be silent in operation.
The real challenge lies with the fact that all these desirable attributes are mutually exclusive. It’s not possible to develop a brake pad that will work perfectly on the road, performs great on track, has huge wear life, produces no dust and is still totally silent in operation. So, in the end the user must make a choice, which often means compromising in some areas to increase performance in others that are more desirable.
ARE THEY ALL THE SAME?
The quality and performance of pads in today’s marketplace varies massively. The good news is that price is usually an indicator of quality, meaning you often get what you pay for. But it’s important to appreciate that better quality pads usually wear much slower, while giving you significantly improved braking performance throughout its longer life – so there really isn’t any logic in skimping when it comes to braking. Think ‘pound-per-mile’, and remember workshop labour rates aren’t cheap, meaning a set of quality pads that lasts twice as long could be saving you additional mechanic’s fees.
There’s an almost bewildering choice out there, but if you speak to the brake pad manufacturer, there will usually be a technician on hand, who will gladly guide you towards making the right choice.
WHAT ARE THEY MADE OF?
Brake pads can contain anything from ten to 30-plus separate ingredients, such as steel fibre, copper, graphite, aramid fibres and rubber – often bound together by a phenolic resin (except in sintered pads, where the metallic ingredients are fused together under immense heat and pressure).
Carbon brakes aside, pads can generally be split into two types: organic and sintered. There are also semi-metallic pads, which fall somewhere between the two.
Organic pads are typically quiet, very kind on discs, produce minimal brake dust and have excellent pedal feel. The drawback of organic brake linings is that it’s challenging to produce a pad that will maintain performance at very high temperatures (the organic resin breaks down, which leads to brake fade).
Semi-metallic pads contain higher levels of steel fibre, which makes them more abrasive on discs and therefore produce more dust, but they are attractive because it’s less of an engineering challenge to maintain braking performance at extreme brake temperatures.
HOW DO AFTERMARKET BRAKE PADS DIFFER FROM OEM VERSIONS?
Almost all OE pads are semi-metallic varieties. They contain abrasives like steel fibre that make them perform pretty well, as well as being cheap to mass-produce. The problem is that they can wear the disc out very quickly. OE semi-metallics are often quite snatchy under braking and are also often unsuitable for fast-road or serious track use. Aftermarket pads, either organic or high performing semi-metallics, aim to increase the friction level slightly, reduce the chance of brake fade, produce lower dust, and should provide a more progressive response to the brake pedal.
Track-only pads take things further still, aiming to provide fade-free performance at the expense of an increase in noise and dust levels. Ultimately, good brake pads will breed driver confidence, allowing the driver to really focus on enjoying driving without the worry of brakes overheating and fading.
WHY, OR WHEN, WOULD YOU NEED TO UPGRADE YOUR BRAKE PADS?
Driving quickly on the road, attending track days, or just generally looking for a lowercost option than a main dealer, are all valid reasons to upgrade to a quality aftermarket pad. Track days, in particular, put much greater strain on the braking system, so fitting high-performance pads before taking to the circuit is essential.
HOW IMPORTANT IS IT TO GET THE RIGHT TYPE OF BRAKE PADS?
Most quality road pads conform to a piece of legislation called R90, which means they are independently tested to be equivalent to (or better than) OE components; so you must ensure any pad you use on the road is R90 approved. If you use a non-R90 compliant pad on the road and your insurer finds out, it will almost certainly invalidate your insurance. Interestingly, though, vehicles with an aftermarket big brake kit can run whatever pads they want, as they then fall outside of R90 regulations.
Legal requirements aside, some (but not all) track pads may need warming up before an acceptable friction level is reached, making them far from ideal for use on the road. The brake pad manufacturer should be your primary source of guidance; they know their products best.
ARE THERE ANY DOWNSIDES TO UPRATED BRAKE PADS?
Assuming you’ve chosen the right pad for how you drive your vehicle, then there aren’t really any downsides. A well-chosen aftermarket pad will often provide increased performance, longer wear life, improved pedal feel, produce less dust, and be a good chunk less expensive than OE parts. The only exceptions are very highperformance pads designed for use on track, which will often be noisier and produce more dust.
WHAT CAUSES FACTORY BRAKE PADS TO FAIL, OR NOT BE SUITABLE FOR THE TASK? DO AFTERMARKET PADS SUFFER THE SAME FATE?
Pads don’t usually fail, but they do begin to fade when they get too hot. Every brake pad has a designed temperature operating range, so it’s important to choose one that’s right for the type of driving you’ll be doing. If the pads are regularly being operated beyond their designed upper temperature limit then you’ll get brake fade, and pad wear will increase considerably.
Applying temperature paint to the edge of the brake disc is a quick and effective way to see what sort of brake temps you’re hitting, and you can then use this info to guide pad selection. As a rule, you should never be frequently reaching temperatures in excess of 650C. If you are, look to direct additional cooling to the brakes via ducting, which is a low cost, low weight-penalty modification.
OTHER THAN ENSURING YOU GET THE RIGHT PAD FOR YOUR APPLICATION, WHAT ARE THE MOST IMPORTANT THINGS TO LOOK OUT FOR WHEN BUYING UPRATED BRAKE PADS?
Aside from being R90-approved, think carefully about where you buy products. Fake pads can look identical but often haven’t been tested or certified, and this can make them very dangerous. Only buy pads in original packaging, check the security seal is not broken, and buy through respected authorised dealers.
Other than that, choose a brand that has good customer reviews, as this shows they’re willing to work with you in the event of you having a problem or a complaint. Modern brake systems are complex, and having friendly and responsive tech support will help you pinpoint any problems you’re having. People often jump to conclusions and blame the new pads, or new discs, but often it’s something else that’s the root cause of the issue.
WHAT OTHER MODS SHOULD YOU CONSIDER WHEN UPRATING YOUR BRAKE PADS?
Performance brakes need quality tyres to transmit the increased braking torque to the tarmac. If you’ve fitted budget tyres then every stop will be grip-limited and your stopping distance is then determined by how effective your ABS is, so you won’t be getting the best from the upgraded brakes.
Braided brake lines are one of the best value mods you can do to a car, as most carry a lifetime warranty, making them a fit-and-forget upgrade.
Quality brake fluid is also essential – it’s quite literally the lifeblood of the braking system. Flush with new fluid no less than every two years, or more frequently for race fluid, which absorbs water more quickly.
The brake pad and brake disc together form the friction coupling, so if either is of poor quality then brake performance will suffer. People often overlook the importance of disc quality. Just because two discs are geometrically identical doesn’t mean they’re the same. The role of the brake disc is to absorb and dissipate heat – it is a heatsink. The composition of the disc can have a profound effect on its ability to conduct heat away from the pads, so a quality disc is important to prevent the pads from overheating.