Why are the RABS systems so hated?

[tx3nc]

i love real abs.....as long as i can turn it off for certain 4x4 adventures


but allan put it just like it is.


these things can be disassembled and cleaned though.

for doing burnouts in the waterbox they are very handy....or just brake bias so you dont need a front locker for mild situations...

great for anything but rabs

You do bring up a good point. With a little hacking on the schematics and understanding of the system, someone could probably come up with a way to engergize the isolation valve in the RABS valve to create a poor-man's line lock. Flip a toggle switch, engage the isolation valve, stand on the brake pedal to lock the font brakes and light the rear tires up.

 

[4.0B2]

mine was bypassed b/c it was bad, and didn't let any fluid to the rear. we drove my b2 about 6 years and my rear pads were BRAND NEW.. lol. now they get used, and i can actually stop a trailer w/out a pucker factor.

 

[tx3nc]

mine was bypassed b/c it was bad, and didn't let any fluid to the rear. we drove my b2 about 6 years and my rear pads were BRAND NEW.. lol. now they get used, and i can actually stop a trailer w/out a pucker factor.

Ok. Thanks for the info. Have you been in a panic stop situation with the valve bypassed? Does the truck have more of a tendency to swap ends now? How is the wear on the rear shoes now, more normall? What about the front pads, are they wearing normally?

 

[4.0B2]

all my pads wear normal. fronts are usually replaced about 1.5x compared to the rear. but the braking seems perfectly solid. everytime i get on my brakes, i STOP. i don't think i've ever locked them.. front or rear, i've been on them HARD. but i guess not that much?? lol.

and we did the same thing on our explorer, and the brakes are MUCHO better. i don't regret it one bit.

i guess i don't really know what you mean when you say "swap ends" but everytime i hit my brakes, no matter how hard-- i just slow down or stop. i've never swung the back end around or anything.

 

[tx3nc]

all my pads wear normal. fronts are usually replaced about 1.5x compared to the rear. but the braking seems perfectly solid. everytime i get on my brakes, i STOP. i don't think i've ever locked them.. front or rear, i've been on them HARD. but i guess not that much?? lol.

and we did the same thing on our explorer, and the brakes are MUCHO better. i don't regret it one bit.

i guess i don't really know what you mean when you say "swap ends" but everytime i hit my brakes, no matter how hard-- i just slow down or stop. i've never swung the back end around or anything.

Yes, by swap ends I mean locking up the rear brakes and ending up in a skid that turns into a spin. I've been in this sistuation several times in a pickup truck. Usually in an unloaded truck in a low traction situation (rain, snow, or ice). It's due to the rear brakes locking up before the fronts and the tires that are sliding have less friction than the ones that are still rolling. Any side force on the truck (ie, in a turn) and the locked wheels want to be in the front, so the rear end comes around and you're suddenly going backwards.

Thanks for the information. My reason for asking is when I look at the Ford service manual for my '93 Ranger with ABS, there is no proprotioning valve shown to balance the brake bias from front to rear. It seems to me, the proportioning valve funciton has been taken over by the RABS valve. By bypassing that valve, one would end up with a brake system with no proportioning valve.

 

[4.0B2]

i've never had problems. mine is a b2, and the explorer.. so not a pickup. more weight on the rear. i have no clue if that matters at all...

but in my opinion from my own personal experience i've never had a negative effect from bypassing the abs.

 

[bryanb]

Thanks for the information. My reason for asking is when I look at the Ford service manual for my '93 Ranger with ABS, there is no proprotioning valve shown to balance the brake bias from front to rear. It seems to me, the proportioning valve funciton has been taken over by the RABS valve. By bypassing that valve, one would end up with a brake system with no proportioning valve.

My '89 Ford shop manual eludes the same thing. I was thinking that the proportioning must be done in the master cylinder, since so many report not-bad results with bypassing the RABS.

 

[tx3nc]

i've never had problems. mine is a b2, and the explorer.. so not a pickup. more weight on the rear. i have no clue if that matters at all...

but in my opinion from my own personal experience i've never had a negative effect from bypassing the abs.

I think the B2 does have a better weight distribution than a pickup with an empty bed. I agree, that probably has a lot to do with it.

 

[tx3nc]

My '89 Ford shop manual eludes the same thing. I was thinking that the proportioning must be done in the master cylinder, since so many report not-bad results with bypassing the RABS.

I don't know. I don't think the master cylinder has any proportioning characteristics. In THEORY the RABS should be a better option to a fixed proportioning valve in a pickup. Since the weight distribution can vary significantly due to the truck being loaded or unloaded, it is not possible to make a static proportioning valve that will work in all situations. GM tried with a proportioning valve that had a linkage to sense how much the truck sagged if it was loaded. But a mechanical linkage is subject to wear and eventual slop in the linkage. An electronic RABS system wouldn't suffer from that and would always be proportioning the brake force to optimally apply the rear brakes depending on wheel speed vs load in the truck. Now as I said, that is just my theory. It seems that in the real world, it either isn't working out that way, or the system is not being understood or maintained how it needs to be.

 

[makotoseven]

if you think it doesn't do anything delete it and drive your truck at highway speeds.

now try to stop suddenly. notice how your rears lock up but your fronts aren't doing much? thats what the RABS prevents constantly. it modulates the rear brakes to keep them from locking up when you stand on the brakes.

i have a 92 single cab that i just replaced mine on and i only did it because of the massive rear brake bias. yeah, i could've installed a brake bias valve or something but it was a cost/benefit thing.

 

[4.0B2]

if you think it doesn't do anything delete it and drive your truck at highway speeds.

now try to stop suddenly. notice how your rears lock up but your fronts aren't doing much? thats what the RABS prevents constantly. it modulates the rear brakes to keep them from locking up when you stand on the brakes.

i have a 92 single cab that i just replaced mine on and i only did it because of the massive rear brake bias. yeah, i could've installed a brake bias valve or something but it was a cost/benefit thing.

really? b/c mine stops just fine at interstate speeds..

 

[gw33gp]

The RABS system seemed to work as designed on my 89 STX. As I see the old RABS system cycles at much slower rate than the new ABS system and did not work as well. I think it was still a good safety system for a 'light in the rear vehicle' but it was early in the development stages and had much to be improved.

I think the first time mine activated the RABS light came on and I had to replace the control module. It was an easy fix and not too expensive but it only had about 60K miles on it. It continued to work the remaining of the nearly 200K miles that I drove it.

 

[adsm08]

The biggest failing of the early RABS systems, pre-1995 or so IIRC, is the system's inability to cycle. There was no pump on them to replenish the system, so when it goes off and you empty the unit's internal reservoir, that's it, you are back to normal braking until you release the pedal and hit it again. It wasn't even a failing so much as a design limitation. But as was said, it is a first-go at this kind of thing.

My biggest problem with RABS is that I see it as pointless. Even in my truck I have never ever locked up the rear wheels before the fronts. And I have stood on the brakes at 80 MPH when a BMW cut me off coming onto the highway. Front wheels locked, rear jumped off the ground, but never left skids on the ground.

ABS does overall increase needed stopping distance though. Modern systems are also designed to keep the driver from loosing steering when the wheels lock up. If I am not going to keep my steering, I don't want a more complex system that makes me keep pumping the pedal anyway and breaks more, when I can do the same job myself. I have never needed ABS, and even on the vehicles I have owned that did have it, I have never had a genuine ABS activation event.

I had it activate a few times on the S-10, but the system was a bit wonky and would go off when it wasn't needed. Most of the activations I did have in that truck were on purpose trying to find the problem anyway.

 

[tx3nc]

really? b/c mine stops just fine at interstate speeds..

Are you talking about your Bronco? Is it possible the weight distribution is closer to 50/50 in a Bronco as compared to a pickup truck?

 

[4.0B2]

Are you talking about your Bronco? Is it possible the weight distribution is closer to 50/50 in a Bronco as compared to a pickup truck?

the b2 and explorer. My father and I have bypassed them on full size pickups also. We've never had an issue byassing it.