I have never had much confidence in self-adjusters.

I was always told that you were to pump the brakes ON-OFF-ON-OFF while slowly going backwards to make them self-adjust.


I will also restate my frequent advice to remove the star-wheel adjusters, completely dis-assemble them, wire-wheel brush them, sharpen the teeth with a triangle file, and coat the threads and all moving parts with a generous application of anti-seize.

If the adjusters are not lubed up with anti-seize, they will rust themselves tight and will not adjust, either by self-adjust, or by brake-tool.

 

Do you use regular or the high-temp copper-based anti-seize? Do they get hot enough to warrant the copper stuff?

 

I have never been able to find the copper stuff anywhere around here.

The silver stuff has always been right there, throughout the duration of a set of shoes, and could go much longer.


I have often used the silver stuff on such things as manifold bolts and turbo-flange bolts and it has always stayed right where I put it.

That copper stuff must be for some really high temperatures.

 

In all respect, I am going to have to respectfully dis-agree with that statement.

I believe that once you think about, you will agree.



The RWAL has no notion of whether the wheels are on or off the ground, nor whether the truck weighs nothing or ten tons.

All the RWAL knows is if or if not the rear wheels are rolling, due to that tone-ring thingie riding behind the ring-gear.


The RWAL quits applying rear brake pressure WHEN THE REAR WHEELS STOP TURNING, such as when they are locked.

If the rear wheels are still turning, even when the wheels are in the air, then a working RWAL will apply fluid pressure to the rear brakes until the wheels once again quit rolling.




One other point to consider :

Due to the behavior of even a perfectly working RWAL or any anti-lock system, they are deadly dangerous when trying to hold a load on a hill, especially when the truck is pointing up-hill and wanting to roll down-hill.

 

A little clarification if I may: The RWAL computer doesn't just look to see if the rear wheels are rolling or not and the actuation of the valve is not controlled on that basis. The computer looks at the rate of change of speed of the rear wheels and determines, based on the programing that is loaded into the computer, if the wheels are slowing too quickly (IE. if the wheels are slowing faster than the best possible performance of the entire truck at light load). If the rears go from say 40mph to 0mph in .5 seconds, the computer knows this is not possible unless the rears are sliding and so tells the RWAL to release pressure to the rear wheels until they come "back inside the curve" so to speak and then closes the valve and allows pressure to build in the rears again. For this to work you must continue to apply the pedal which will drop further than under normal operation but has enough reserve travel to accomodate the additional fluid needed to re-apply the rears. It is a nervous making feeling for sure, but the key is to just push that pedal for the floor and the truck, if everything is within spec, will stop in the best possible distance and most importantly, in the direction the driver chooses, and not sideways or backwards. It doesn't feel like it but after 20 years of professionally testing brakes I have the seen the data and the data doesn't lie.

Also, the ABS does not function under about 5 mph, thus when stopped you have full pressure to the rear brakes regardless of what surface, angle etc. you may be stopped on.

That being said, it's a crummy system and feels like dog dookie even when it's functioning perfectly which is why the rear only ABS (RABS) didn't have a very long run. All the OEMs went to a three or four channel (front and rear) after only about 5 years which is a short run in this business. It was, however, cheap and easy to add to an existing platform and certainly better than a hight sensing prop valve which are even more trouble prone than what we got.

The reason the system is designed this way is to allow enough brake to be installed on the rear axle to meet stopping distance requirements when the truck is at gross vehicle weight without overpowering the rears at light load. The RWAL is in effect being used as a proportioning valve, allowing lots of brake while loaded and preventing rear lock when not loaded.

A thought about bypassing the valve: The system is not designed to operate without the valve, if you take the valve out of the system, the brakes become unbalanced, biased to the rear. This can be corrected with a manual proportioning valve installed in the rear brake line but requires diligent adjustment to account for weight changes. Kind of a pain in the butt if you ask me. Also, especially for you commercial guys, if you are involved in a fatality accident, and the opposing lawyer is on the ball at all, they will want to inspect your truck. If they find a disconnected or bypassed RWAL... Well, get out your check book because your insurance won't cover it.

In my opinion, both personal and professional, it's worth the hassle and expense to make the system work properly.

OK. Flame on!

 

No flame, just respectful disagreement, because that is how we roll on DTR ...Mark

 

[QUOTE=BearKiller;2988602]In all respect, I am going to have to respectfully dis-agree with that statement.

I believe that once you think about, you will agree.



I went to Chrysler school on this system a thousand years ago. This "Anti lock" system is a FAR cry from the modern Bosch designed systems we have today.
Per the service manual... "The system will provide vehicle stability by allowing at least one rear wheel to remain unlocked"
The "At least" part is due to open, or Trac Lock diffs. The system WILL NOT allow the ring gear/differential to completely stop turning by dumping the pressure in the rear wheel circut to zero, if nesc.

This was a crude system, at best, and has ABSOLUTELY NOTHING to do with weight, tire size, vehicle height, etc. all it does is dump the pressure to the rear circuit if it senses the rear axles are ABOUT to stop turning.

The 5mph reference is to check the output of the sensor (650 MV or more)

I like a good, healthy debate!

 

I believe that my 01 1500 had rear-only ABS. Dad had a 98 1500 V6 with 4-wheel and it had a lot more lines and a much bigger ABS pump than my 01 did.

We also had a 98 2500 and 2000 1500 V6, with rear-only, and to get the 00 stopped, we had to pull the ABS relay, but then it ate rear brakes.

After a panic stop you would have to peel your face off the windshield of my 01. The 2500 stopped OK, but nothing spectacular. The 00, you were lucky most days if it stopped, and the 98 with 4 wheel, well, you'd have to peel your face off the windshield and mop up some blood.

So even in later years, from one truck to another, braking performance was inconsistent.

 

Hey Scot Pa, how's it goin'.

I think at least part of the difference you're seeing is due to the 1/2 ton vs. 3/4 ton systems. The 3/4 system is a completely different animal...Bigger brakes, higher payload...maybe most importantly a larger spread between unloaded and GVW.

Unloaded, the front brakes on a typical standard cab long bed 3/4 or larger truck do nearly 80% of the work. The rears are mostly along for the ride. Loaded it's much closer to 50% - 50%. The split is much less for a 1/2 ton in terms of performance, thus the 1/2 ton uses a smaller rear brake which is inherently more balanced even without operational ABS.

Keep in mind as well that all this testing is done with new or prototype vehicles, so twenty years down the road there is a lot of opportunity for things to have deteriorated and performance to have changed through the use of aftermarket friction with different performance characteristics, aftermarket rotors and drums, mis-adjustment, poor maintenance...who knows.

I'm just trying to put out some real, data based info for the people who are interested in what the factory intended. What anybody decides to do with that info is up to them. There will always be another way to skin the cat, some good, some not so good...as for me, I don't even own a cell phone or get digital TV, but if I thought I could retro fit 4-wheel ABS to my truck and tune it correctly I would. Problem is that Bosch spends (I would guess judging from the development programs I've worked on) somewhere around 5 to 8 thousand man hours on any given vehicle line, more depending on the number of variants.

So I'm stuck with what they gave us...I just want it to work as well as possible...I know there are others out there who do as well and half the battle is getting past the "some guy said" stage and understanding how the system actually works.

On a side note: I'm absolutely positive that I can convert any non-ABS beliver to a ABS missionary in 2 minutes and 2 stops on a wet tile/dry concrete split mu (friction) skid pad. 2 stops, one ABS on, one ABS off, gaur-een-teed.

 

That ABS junk may work well on a controlled environment skid-pad, but it sure will scare the britches off of anyone not used to it that is hauling heavy trailers in hill country; I will stick by my old school brakes and vacuum-over-hydraulics on the trailers; the only thing better, and they are light-years better, is air-brakes.

I have had my license for more years than most of you guys have been alive and I ain't rear-ended nobody yet.

 

Totally agree! For the most part, just paying attention is 99% of the battle. I prefer threshold braking MYSELF over a computer doing it for me. Plus, in heavy snow, I found the ABS cars I was road testing would actually take longer to stop!
ABS has probably hurt as much as it has helped because when someone who is not aware of what the brake pedal does when ABS activates tends to jump off the pedal due to surprise!
Now, for 2012, ALL vehicles MUST have Stablity control, and you cannot turn it off, no steering with the throttle anymore.

 

Interestingly enough I agree with both Bearkiller and Thunderhog. I agree with Bear when he makes the point of ABS scaring the britches off anyone not used to how it works. I think every dealer should have a little skid pad on the lot and everybody who buys a car with ABS should have a little ten minute training session before they leave the dealership.

There are several studies that show exactly what thunder is talking about. People do tend to jump off the pedal when the feedback occurs because nobody has told them how to drive the system. It's not a hardware issue, again, look at the data, it's a training issue. Another study, designed to see what people do in emergency situations found that the vast majority, even when briefed on how ABS works (it lets you have maximum braking and still steer the car) smacked the pedal and drove straight into the obstacle never even trying to steer around it.

You know what Forrest Gumps mama said.

So guys, run what you're comfortable with, I'll take a well trained driver that's paying attention over a safety system that's being used improperly any day of the week. All I'm saying here is, don't blame the hardware and please allow some space for the folks that want to do it differently than you.

 

I was lucky enough to have gone through police pursuit training when I was training to be a fire investigator. During the training we were doing various panic stops with abs cars and with non abs cars. The biggest difference for me was the "rattle" in the pedal when the abs activated., otherwise I was able to stop straight, without skidding with either one. I am with anyone that says paying attention while driving is 1000 times more important than any abs system. If anyone remembers my near miss in a fatal, dust storm, multi-car collision during Christmas 2009,in AZ, the only reason that I was able to stop without hitting anything is because I was paying attention and slowed down at the first indication of trouble, which was a little dust blowing in the wind. .Less than 30 seconds later and there was zero visibility.No abs system in the world would have helped if they were not paying attention. People drive too fast for the existing road conditions, while putting on make-up or talking on a cell phone, instead of DRIVING their car. I guess that I am sorry for it, but most people in accidents, whether deemed their fault or not, could have avoided the accident if they had been paying attention. That opinion was formed by 26 years of scraping people off the asphalt. That said, there should be NO WAY that a supposed "safety system" should EVER allow the brakes to fail, lack of maintenance or no. The engineers that designed this system should be ashamed of themselves, but more likely they are enjoying their retirement in Barbados...Off soap box...Mark

 

Holy cow! I remember that thread! That was messed up!

 

I took the Wife out to Infineon raceway in her Cheep Jerokee ( Yeah, I hate it too!!!) And showed her EXACTLY what her brakes would do on incipent lockup (Chatter the pedal) she completely let off the brakes due to surprise! She surely would have hit the car ahead in a "panic stop".
That said, I tried to teach her how to never get into a "panic stop". I know that there is always some idiot pulling out in front of you, however, 99% of the time, it can be anticipated. She does drive different now!