Mikeyfly7
Registered User
Does anyone know how a 2 wheel abs works with no front wheel sensors to differentiate the wheel speed between the front and rear?
2 wheel abs
- Thread starter Mikeyfly7
- Start date
Basically if you don't have a 4X4 or a vehicle with front wheel drive, there is no need for front wheel sensors and/or ABS control. On a rear wheel drive vehicle the ABS module senses the rotational speed of each wheel and compares it when the brakes are applied, if one wheel is slower than the other, the ABS unit pulses, releasing the brake pressure to the slower rotating wheel, that's why you feel something like a rumble as long as the brakes are applied, braking pressure goes back and forth between each wheel until the brakeing is released.
Double-S-Diesel
parts seller
front wheels will lock, rear wheels wont, that is the difference between 4wabs and 2wabs
Mikeyfly7
Registered User
Hey guys, I appreciate the answers but I do have a 4x4, and also there are no individual rear wheel sensors, it just has the speed sensor that reads off of the tone ring in the rear differential. With this being said my question is, how could it read between each rear wheel as to whether there is a skid between them. I know that in a 4 wheel abs each wheel has a speed sensor that sends a signal to the computer that indicates a difference in wheel speed between all 4 wheels. Again forgive me guys, I'm still not quite understanding how this works.
Matrix37495
The Amish Wolfman
I would assume it monitors the rate at which the rear axle slows and compares that to a set threshold... The computer would know that a 5,000#+ truck can only slow so fast, so if the rear axle stops right away then it would assume a skid....
Edit:
FSM 06-09A-1
"When the brake pedal is applied, the RABS II module senses the drop in rear wheel speed. If the rate of deceleration is too great, indicating that a wheel lockup is going to occur, the RABS II module activates the electro-hydraulic valve causing the isolation valve to close. With the isolation valve closed, the rear wheel cylinders are isolated from the master cylinder and the rear brake pressure cannot increase. If the rate of deceleration is still too great, the RABS II module will energize the dump solenoid in a series of rapid pulses to bleed off rear wheel cylinder pressure into an accumulator built into the RABS II valve. This will reduce the rear wheel cylinder pressure and allow the rear wheels to spin back up to vehicle speed.Continuing under the RABS II module control, the dump and isolation solenoids will be pulsed in a manner that will keep the rear wheel rotating while still maintaining high levels of deceleration during braking.
At the end of the stop, when the operator releases the brake pedal, the isolation valve de-energizes and any fluid in the accumulator is returned to the master cylinder. Normal brake operation is resumed."
Edit:
FSM 06-09A-1
"When the brake pedal is applied, the RABS II module senses the drop in rear wheel speed. If the rate of deceleration is too great, indicating that a wheel lockup is going to occur, the RABS II module activates the electro-hydraulic valve causing the isolation valve to close. With the isolation valve closed, the rear wheel cylinders are isolated from the master cylinder and the rear brake pressure cannot increase. If the rate of deceleration is still too great, the RABS II module will energize the dump solenoid in a series of rapid pulses to bleed off rear wheel cylinder pressure into an accumulator built into the RABS II valve. This will reduce the rear wheel cylinder pressure and allow the rear wheels to spin back up to vehicle speed.Continuing under the RABS II module control, the dump and isolation solenoids will be pulsed in a manner that will keep the rear wheel rotating while still maintaining high levels of deceleration during braking.
At the end of the stop, when the operator releases the brake pedal, the isolation valve de-energizes and any fluid in the accumulator is returned to the master cylinder. Normal brake operation is resumed."
Last edited:
If you would put that it's a 4X4 in your damn sig, or said so, it's a whole new ball game.
Matrix37495
The Amish Wolfman
^?
4wd wouldn't matter to RABS unless it was actually in 4wd...
4wd wouldn't matter to RABS unless it was actually in 4wd...
Mikeyfly7
Registered User
I apologize Old Bull, I realized after reading what I wrote that I did indeed leave out quite a bit of info on the subject. Please forgive me sir.
Double-S-Diesel
parts seller
4 wd or 2wd doesnt matter 4 wabs, or 2wabs, othe than the abs is inactive in 4 wd.
as for the rear wabs, only having one sensor, basically if one wheel locks up the differntial quits spinning and the sensor dectects lock up.
as for the rear wabs, only having one sensor, basically if one wheel locks up the differntial quits spinning and the sensor dectects lock up.
As far as i know cars that have abs has four wheels abs not just front dealer dont know about cars they selling cars maybe he was saying abs brakes not much better than regular brake system or maybe they about the same has but far as i know of any car that has abs its all four wheels any most every new car wil have abs= antilock brake system front wheel drive or not
