Brake pads are used to stop moving vehicles; they do this by converting the kinetic energy of a moving vehicle into heat. How effectively brake pads generate heat will determine how well they work.
It is important to choose the right brake pad for the correct application. There are 3 main variables that affect brake performance.
Braking performance can be improved (or made worse) by changing any one of the above components of the braking system. Pad Certification
OE brake pads and aftermarket brake products In UK, Europe, USA (actually most places in the world) are made to a very high standard.
ECE R 90 - certify that the replacement brake pads are at least equal to or better than OE parts. Test for performance, cold performance, bedding in.
ABE (TÜV) – replaced by ECE R 90 for brake pads but still valid for brake discs.
AMECA (US) – friction material testing and registration, edge coding
It is illegal to sell uncertified braking products in most countries. Insurance companies will refuse to pay out compensation after an accident if un-certified braking products were used on a vehicle involved in an accident.
There are a number of ways friction materials can be affixed to brake pad back-plates.
A common problem with brake pads is edge lifting, leading to brake noise or even separation of brake material from the back-plate. This is often caused by moisture ingress (resulting in rust) or bond failure.
Methods of attachment:
Slots in the friction material help reduce water and gas fade and also help the pad wear evenly
Chamfers are added to brake pads to reduce vibration (noise) and help for a faster bedding in (run in)
Electronic sensors which operate a warning light or OBC message when the pad is low work by completing a circuit when the sensor touches the disc because the brake pad has worn thin (common on European cars).
Screech pin, is a metal strip which touches the disc when the brake pad gets thin and makes a noise.
Different brake pad materials give a different brake pedal feeling and different performance characteristics.
A metal based pad may feel hard and grabby where by an organic pad feels soft and has the feeling that it is sucking the pedal or foot as the vehicle slows down.
Choose a brake pad that suits your vehicle.
A high performance track pad may not be correct for an eco-car used in the city as it may not generate enough heat to work in its effective friction-heat range.
Choose a pad that suits:
Brake systems generally use synthetic glycol based brake fluid. All Glycol brake fluids are ‘Synthetic’
DOT 3, DOT 4 , DOT 5.1 & High boiling point (Racing grades) DOT 4 fluids. DOT LV (Low viscosity grades) for ASC.
All these fluids can be mixed, however if you mix DOT 3 with DOT 4 you will lower the boiling temperature.
All DOT 4 fluids are not the same. Do not just look at the boiling point, consider the viscosity to. Higher viscosity brake fluids give a firmer pedal feel.
Viscosity can range from 750 cSt to 1800 cSt.
Note: The boiling point of brake fluid can drop by 100 degrees C with just 3 to 4% moisture content. A brake system can easily absorb 3 to 4% of moisture in 1 year. Change your brake fluid every year.
Brake discs should only be ground on the car. By removing the discs and grinding them on a lathe you are in fact machining them out of alignment with the car. Brake discs ground off the car will take much longer to run-in and may cause other issues such as brake noise. Do not grind the disc If the brake disc is not too badly worn or there is no on car grinding available.
EBC Brakes recommend Pro Cut brake lathes https://www.procutusa.com/
Use the vehicle normally, avoiding heavy, unnecessary braking where possible for the first 300 or 400 Km.
If accelerated bedding in (run-in) is needed, then:
EBC Brakes road pads have a run-in coating that conditions the surface of the disc and removes the old brake material deposits, this can correct issues such as brake judder caused by uneven deposits of brake material and lasts for around 500 km.
New brake pads can take between 1000 and 2000 Km to fully run in. Problems such as excessive pad noise should not be addressed until after this period.
Good quality, certified brake pads will state the friction code somewhere on the plate. This code is expressed as 2 letters (G-G for example). The first letter denotes the friction at a ‘normal temperature range’ (this being 93-204 deg C (200-400 deg F)) and the second letter denotes the amount of friction at high temperatures (148-343 (300-650 deg F)).
Note that some pads may display a high friction rating, but it’s important to look at the friction beyond 350 deg C. Does it drop off quickly? Does the friction level continue for another 100 or 200 degrees? Or does the friction level increase with the temperature?
EBC Brakes Ultimax 2 is a GG rated organic brake pad. At 450 deg C it can be seen here still giving high (0.5 mu) friction in continuous use. This pad is still effective at 600 deg C.
Does brake pad quality really matter when we have ABS? Is it possible to reduce braking distance on cars with ABS? Yes,. Here’s why…
A skidding car takes a longer distance to stop than a car braking on the edge of grip.
A car skids because the brakes have overcome the friction of the tyres on the driving surface. The brakes have overcome the friction of the tyres because of a change in the road surface, a shock application of brakes, or the brake pad material has a grabby nature. The ABS stops a skid by releasing the brakes and re-applying them
A car stopping under ABS takes a longer distance to stop than a car braking on the edge of grip.
A brake pad that does not grab, has a higher friction then OE and is progressive in character can improve braking on cars with ABS as it is allowing greater pressure transition to the brake disc before locking up.