Characteristics of Traction Control

VEHICLE PERFORMANCE DURING ABS
This ABS Brake System represents current state of-the-art in vehicle braking systems. It offers the driver increased safety and vehicle control during hard braking. This is accomplished by a sophisticated system of electrical and hydraulic components. As a result, there are a few performance characteristics that may at first seem different but should be considered normal.

NORMAL BRAKING SYSTEM FUNCTION
Under normal braking conditions, the ABS System functions the same as a standard brake system with a diagonally split master cylinder and conventional vacuum assist.

ABS SYSTEM OPERATION
If a wheel locking tendency is detected during a brake application, the system will enter ABS mode. During ABS braking, hydraulic pressure in the four wheel circuits is modulated to prevent any wheel from locking. Each wheel circuit is designed with a set of electrical valves and hydraulic line to provide modulation, although for vehicle stability, both rear wheel valves receive the same electrical signal. The system can hold, build and reduce hydraulic pressure at each wheel brake. Depending on signals generated by the wheel speed sensors (WSS) at each wheel and received at the Controller Antilock Brakes CAB.

During ABS Braking, brake pressures are modulated by cycling electric solenoid valves. The cycling of these valves can be heard as a series of popping or ticking noises. In addition, the cycling may be felt as a pulsation in the brake pedal. If ABS operation occurs during hard braking, some pulsation may be felt in the vehicle body due to fore and aft movement of the suspension as brake pressures are modulated. Although ABS operation is available at virtually all vehicle speeds. It will automatically turn off at speeds below 3 to 5 mph. Wheel lockup may be perceived at the very end of an anti lock stop and is considered normal.

VEHICLE HANDLING PERFORMANCE DURING ABS BRAKING
It is important to remember that ABS does not shorten a vehicle's stopping distance under all driving conditions, but does provide improved control of the vehicle while stopping. Vehicle stopping distance is still dependent on vehicle speed, weight, tires, road surfaces and other factors. Though ABS provides the driver with some steering control during hard braking, there are conditions however, where the system does not provide any benefit. In particular, hydroplaning is still possible when the tires ride on a film of water. This results in the vehicles tires leaving the road surface rendering the vehicle virtually uncontrollable. In addition, extreme steering maneuvers at high speed or high speed cornering beyond the limits of tire adhesion to the road surface may cause vehicle skidding, independent of vehicle braking. For this reason, the ABS system is termed antilock instead of anti-skid.

NOISE AND BRAKE PEDAL FEEL
Brake pedal feel during normal braking, if the vehicle is equipped with the Teves Mark IV-G ABS or Traction Control system, is the same as conventional Non ABS equipped cars. When ABS is activated during hard braking due to a wheel lockup tendency. Brake pedal effort will increase due to the master cylinder pressure being isolated from the brake system. Some brake pedal movement and associated noises may be felt and heard by the driver. This is normal of ABS due to pressurized fluid being transferred to and from the wheel brakes.

TIRE NOISE AND MARKS
Although the ABS system prevents complete wheel lock-up, some wheel slip is desired in order to achieve optimum braking performance. During brake pressure modulation, as brake pressure is increased, wheel slip is allowed to reach up to 30%. This means that the wheel rolling velocity is 30% less than that of a free rolling wheel at a given vehicle speed. This slip may result in some tire chirping, depending on the road surface. This sound should not be interpreted as total wheel lock-up. Complete wheel lock up normally leaves black tire marks on dry pavement. A vehicle equipped with ABS though, will not leave dark black tire marks since the wheel never reaches a locked condition. Tire marks may however be noticeable as light patched marks.