Brake Discs and Pads
There are several approaches to improving braking performance.
- Upgrade materials
- Improve heat dissipation
- Increase braking pressure
- Increase frictional area
- Increase frictional radius
- Sophisticated ABS that shifts braking effort to the wheels with most grip
- Quality brake discs and pads
Standard brake systems often suffer from brake fade. Under hard or repeated braking, the disc’s and pads heat up quickly and loose there effectiveness. As efficiency is lost, the force or duration of braking applied by the driver is often increased. This worsens the situation, until eventually complete failure is possible.
A spongy feel in the brake pedal is sometimes due to flex in the brake lines. The rubber hoses to the wheels are the usual suspects. Braided hoses are a lot less flexible, resulting in a firmer pedal action and instant response. Although, the sponginess can be compensated for by more foot pressure, confidence and braking control are improved.
Often simply changing the ancient discoloured brake fluid is a very good start, but many manufacturers offer uprated brake fluids that do not age or compress like standard fluids.
Many companies offer uprated brake pads. They are designed to be a direct replacement for the standard items. Manufacturers produce pads in a variety of compounds.
- Fast road pads are designed for tuned road cars (perform well at low to medium temperatures)
- Rally formula pads are designed for rally and light track use.(slightly higher operating temperature range)
- Race formula pads are only suitable for hard track use. (most effective at the extreme temperatures ranges & would perform very poorly at low temperatures)
For road cars, where the temperature is never going to reach that of race cars, ‘Fast road’ pads are the best option. They have a much lower optimum range, so they are effective when cold as well as under hard use.
Machined disc’s will perform the same as standard disc’s when driving normally. Over time and under hard driving the difference may become apparent.
Grooved Disc’s are so called because they have grooves in them:
- (-)More vibration through steering wheel
- (+)Help de-glaze pads
- (+)Higher friction between pad and disc (especially over time)
- (-)Higher rate off wear
Cross drilled disc’s are so called because of the holes drilled into or through them:
- (+)Faster Heat Dissipation
Drilled and grooved disc’s combine both technologies. After market disc’s are also available in different materials such as high carbon steel that do not retain so much heat.
Larger Diameter Disc’s
As everyone knows a big circle has a larger circumference than a small circle. Therefore, if you were to un-roll both circles and lay them next to each other, it would be clear to see a brake pad would have a much greater frictional distance to cover on the big circle. If you spun a wheel, to stop it you would rub your hand against the outside not the hub. Rubbing the hub would not slow the wheel much in comparison with rubbing the larger tyre.
The limiting factors on the size of brake disc are:
- Wheel diameter
- Wheel offset
- Wheel shape
- Wheel width
- Brake calliper size and mounting
- Large disc’s are heavy and can upset handling
|Wheel Diameter||Brake Disc Diameter|
Large diameter disc’s are often made in two or more parts. The central bell is usually machined aluminium, designed to reduce weight, resist rust and disperse heat. Some designs even encourage air flow onto the braking surface by fanning the air.
Many standard callipers have only one piston. Pressure is not asserted evenly over the surface. Multi-pot callipers offer a much greater distribution of pressure. To increase the contact area between pad and disc, a bigger calliper is needed. If a standard sized calliper were to be used on a larger diameter disc, an area of the disc would never be used and would simply rust over.
One of the reasons for going 5 stud Granada was to utilise modern braking components from Audi, Mercedes and Porsche.
Cars with 5x112mm P.C.D.
|Seat||Alhambra||96→||35 to 45mm||57.1mm|
|VW||Golf Mk5||03→||40 to 45mm||57.1mm|
|VW||Passat||00→||35 to 45mm||57.1mm|
|VW||Passat(5 stud)||97→00||35 to 45mm||57.1mm|
|VW||Phaeton||02→||35 to 45mm||57.1mm|
|VW||Sharan||96→||35 to 45mm||57.1mm|
|VW||Touran||03→||35 to 45mm||57.1mm|
|Audi||100/200||90→94||35 to 45mm||57.1mm|
|Audi||A3||03→||42 to 50mm||57.1mm|
|Audi||A6||94→||35 to 45mm||57.1mm|
|Audi||A8||02→||35 to 45mm||68mm|
|Audi||A8/S8||94→02||35 to 45mm||57.1mm|
|Audi||S4||98→||35 to 45mm||57.1mm|
|Audi||S6||94→||35 to 45mm||57.1mm|
|Ford||Galaxy||95→||35 to 45mm||57.1mm|
|Ford||Granada/Scorpio/Ultima||86→94||35 to 45mm||63.4mm|
|Mercedes||190 W201||85→93||35 to 42mm||66.6mm|
|Mercedes||190 W201||85→93||35 to 42mm||66.6mm|
|Mercedes||A Class||98→||45 to 50mm||66.6mm|
|Mercedes||C Class W202||93→00||35 to 42mm||66.6mm|
|Mercedes||C Class W203||00→||35 to 42mm||66.6mm|
|Mercedes||CL Class W215||99→||35 to 42mm||66.6mm|
|Mercedes||CLK W208||97→||35 to 42mm||66.6mm|
|Mercedes||E Class W124||92→95||35 to 42mm||66.6mm|
|Mercedes||E Class W210||95→03||35 to 42mm||66.6mm|
|Mercedes||E Class W211||03→||35 to 42mm||66.6mm|
|Mercedes||M Class ML270/320||98→||66.6mm|
|Mercedes||M Class ML430/55||99→||66.6mm|
|Mercedes||S Class W140||94→99||35 to 42mm||66.6mm|
|Mercedes||S Class W220||99→||35 to 42mm||66.6mm|
|Mercedes||SL Class R129||96→01||35 to 38mm||66.6mm|
|Mercedes||SL Class W230||01→||35 to 42mm||66.6mm|
|Mercedes||SLK R170||01→||35 to 42mm||66.6mm|
|Mercedes||V Class W108 (Vito)||99→||35 to 42mm||66.6mm|