Broken slack adjuster

[Jon]

My last two buses had ABS, but as a homebuilder knows the available coaches are not all going to be 50 year old GMs so that ABS knowledge is valuable.

Truth be known an ABS system is the epitome of simplicity and nothing to be afraid of. If a sensor detects a wheel is slowing faster than the others it tells the "brain" and the "brain" responds by activating the ABS valve. All that valve does is block air flow to the brake chamber from the braking system relay valve, and open the side that has air pressure in the brake chamber, essentially releasing the brake until the speed of the wheel matches the others. When the speeds are the same the system goes back to normal.

Obviously there is pulsing until all the wheels are in concert.

[belfert]

I have ABS on my tag axle only and I hate it.  It hasn't worked since the day I got the bus and the ABS bulb long ago burned out from being on all the time.  I tested the sensors with an ohm meter and they seem to show the right ohms.  I think the electronic box is dead and the box is long obsolete.  The best Bendix or anyone can tell me is to replace it with a box for a trailer.  I just live without ABS on the tag axle because all it does is stop premature locking up of the tag axle brakes.

I took the Bendix class, and while it is good, it was not really what I hoped for.  I was hoping for a little less theory and more practicality.  They really didn't talk much at all about the wheel end stuff which has been all of my problems.  A local tech college has a diesel mechanic program and I've tried to see if they would let me in just the air brake class, but the air brake class apparently is only offered once every two years.

[jetart]

So,  like some cars, does a bus ABS system increase your stoping distance by up to 60%? I realize it has benefits in skid control but I've found it's really not at all helpful when you really want or need to STOP.

[Jon]

Having lived in the western NY snow belt in a previous life I spent a lot of time driving on snow and ice covered roads. At the time the rule that was often stated was in a panic stop hit the brakes hard and do not lift your foot. When you do that you hear and feel the ABS pulsing. Every time you get that pulsing the ABS system is alternately applying and releasing the brakes.

If you are sensitive to what your vehicle is doing you can modulate brake pressure to apply stopping force with brake application without the ABS engaging. My gut tells me anytime the ABS is actively regulating the application of brakes, it is also releasing the brakes so there is likely to be some loss of performance compared to the stopping distances a skilled professional driver can do. My gut therefore also tells me that as a non-professional that does not go out every day and practice maximum braking performance under adverse conditions that the ABS is going to do a better job than I can do. Its real advantage is in assuring the driver the braking is controlled which means steering functions will still work and the vehicle is less likely to start sliding in a circle.

[lostagain]

I got the slack adjuster off last night. Everything else downstream from it (S cam shaft, cams, rollers, etc) is in good condition, and moves freely. It is a Haldex P/N 41910768. I can't even find that one on their site, let alone a manual equivalent. It has a      1 1/4" offset, 10 spline, 1 1/2" diameter spline, 7" arm length, 1/2" pin hole. Not very common. I'll be in Calgary this afternoon, and will look in the Fort Gary Industries store. They have lots there, but mostly for trucks. I have to dig out the receipt for the manuals I got a couple of years ago for the front. I think Inland Kenworth got them for me.

JC

[luvrbus]

Check the Euclid site or call Jefferson in OKC same adjuster as on a Eagle,Ed will have the manual or auto adjust if your source fails

[lostagain]

Thanks Clifford,

the control arm pivot is very stiff. The Oring is bulging out. The guts are full of moisture, even though it would still take grease. I have to think that is why it broke. Am replacing both sides on the rear.

JC

[belfert]

So,  like some cars, does a bus ABS system increase your stoping distance by up to 60%? I realize it has benefits in skid control but I've found it's really not at all helpful when you really want or need to STOP.

I've never noticed the ABS on my current car activate on a panic stop on dry pavement.  We are getting off the original topic here. 

My bus ABS has never worked and it was only for the tag axle anyhow.  I would probably make it a priority to get fixed if it was for all of the brakes.  We drove through a snowstorm in 2009 where any application of the service brakes resulted in sliding and ABS would have been nice.  We used the Jake brake because the bus didn't slide when we used that.  We drove at 20 to 25 MPH for a good five hours that time.  We would have stopped, but we would have been stuck there for several days.  We eventually drove out of the storm.

[Jon]

Don't want to tell anyone how to drive, but I have never seen any owner's manual on any truck or bus that does not specifically warn against the use of a Jake or retarder in slippery conditions.