Joined: 24th Apr 2009
Ride: Mazda( kinda FORD..!)
Location: Sydney, Australia
What effects can a replacement brake pad have on the ABS, traction and stability systems?
ABS, TCS and ESC
Everybody who installs or orders brake pads should be asking themselves the following questions:
To understand these questions and evaluate the potential answers, it is first important to have a basic understanding of the various chassis control systems the “wheel brakes” support and what are the operating principles and control strategies they employ. There are essentially five general chassis control systems available on today’s vehicles. On some vehicles they are standard and on others they are options available to the car buyer.
The Five Chassis Control Systems
The control algorithms for all these systems are extremely sophisticated and contain literally thousands of individual parameters that are tuned specifically to the particular vehicle line and brake system used on the vehicle. These parameters are developed, refined and tuned on a large variety of manoeuvres, speeds and road conditions.
It is certainly reasonable to wonder, after all the work to develop a fully integrated set of systems, what happens when a different set of friction material is put on the car, or more commonly, on one axle of the car during service?
To understand the potential effects, we must go a bit deeper into how these systems generally operate. In all of these systems, the computer controller (the brains of the system) is monitoring the vehicle watching for an indication that an undesirable operating condition starts to appear.
These systems closely monitor individual wheel speeds, vehicle deceleration, engine output, steering wheel angle, yaw rate, lateral acceleration and roll rate among many other secondary indicators. The controller uses all of this information to determine very precisely what the vehicle is doing compared to the desired behaviour of the driver. Then a corrective action plan is determined. The brain then commands a “torque change” (or “torque” in engineering shorthand) to the desired wheel brake. The system cannot directly control torque. It can only control hydraulic pressure.
The desired correction may be a torque increase, decrease or hold. An individual torque command is developed for each wheel independently. The hydraulic pressure in the brake system is multiplied by the friction level of the pad resulting in a torque being applied to the wheel.
In the modern vehicle, the wheel brake is challenged to contribute to a great many vehicle driving conditions extending way beyond just stopping the car. The friction material is a very key element in this. To maintain the optimum performance, it is important to understand the implications of the choices that are being offered to consumers and help them make an educated decision.
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