[Peter]

Greg, How do you know the tag axle brakes are not working?

I suspect but would need some additional information that if you are not getting air pressure to the tag axle brake chambers when the tag is down that it is related to the valving that disables the tag axle brakes when the tag is lifted.

The quickest way to confirm that your service brakes on the tag axle are not working is to disconnect the brake chamber air line and step on the brake. If they are not working because of what I said above you won’t hear air leak out or see a continuing pressure drop on the pressure gauge.

I think your coach precedes the years when the tag was equipped with an emergency brake so your tag axle brakes are just a simple brake chamber and not a combo.

I also believe you have manual slack adjusters so it could be the brakes are out of adjustment. To adjust the brakes (which should be done about every 5000 or 6000 miles use a 9/16 wrench and using the wrench push in on the sleeve that surrounds the hex head on the face of the slack adjuster. That allows you to turn the adjusting bolt. Turn it clockwise until the adjusting bolt stops. The brakes should now be applied. Back off the adjusting bolt 1/4 to 1/3 turn. The brakes should now be released and the wheel should turn freely.

You can visually verify proper adjustment by having someone apply the brakes. Watch the pushrod on the brake chamber and note how much travel it has. On a brake chamber the size on the tag axle you should see about 5/8″ of travel. It could be more, but if the travel is so great you see the red band on the push rod it is too much.

Brakes have to be working properly and if not there is a serious safety issue. If you have any doubt about them take the coach to a qualified shop. Our brakes, especially the tag axle lift disabling is not like that on trucks so the shop you select has to understand coaches like ours.

[Tom]

I did mine 1/4 on back and 1/2 on front wheels

[Bob]

I was under the coach watching the movement and had the wife apply the brakes, No movement. I lifted the tags and adjust the brakes as you said and still no movement. I’ll check for air today. I think the drives are automatic adjusters since they look different than the front and tags. Still investigating. So with the wheels off the ground I can hear a slight drag of the shoes when turning them.

[Archived]

Do you know for sure they have worked since you owned coach? Important ? as PO might have by-passed something . You can go to prevostcar with your serial # last letter in it plus last 4 numbers and get a unit specficic air diagram for your coach. Mine for example W-6553. Go to site left side click go down to tech manuals/diagrams air puematic(sp) There is a norgen valve involved (was on my 89) that some have bypassed in the past. If yours have worked since you have owned coach disreguard. Then look toward the r-14 or disable valve when tags or in lift mode. Bob

[Greg]

I agree with Bob about the next possibility being an R12 or R14 relay valve having the signal air blocked by a valve such as Norgren not working.

When you lift the tag that valve is supposed to prevent brake application, but is supposed to be open when the tag lift lever is in the normal position. Take the following with a grain of salt because I am not looking at the pneumatic diagram and I am supposing. When you lift the tag the valve should operate the Norgrens that are between the tag and drive air bags. The path which is normally open should close, and air in the tag air bags should dump and the lift chambers should be presusrized and lift the tag axle. If that is happening I suspect It imght be a problem with the relay valve.

Remember, I am guessing on this one because I haven’t looked at the drawing.

[Archived]

those year models do not have parking brakes on the tag on 40 footer Darrell

[Archived]

Well I made sure the bags were full and the level switch in Drive and the key on, and the tag brakes worked. I think before I didn’t have the key on. The Drive axle has automatics and there was very little movement in fact I could see none one side when the emergency brake was off. After numberous application of the service pedal I started seeing good movement.

Thanks for your help

[Archived]

sometime not much! old grease on auto adjusters make them stiff over years. I have pushed the old out with fresh and renewed adjusters operation. Not a tech expert just experience. Bob

[glen]

The actual length of movement on brake chamber push rods is determined by the size of the chambers. Larger chambers such as 30 or 36 will have a larger acceptable travel than a 16 or a 20 for example.

I believe on the Bendix site they have the acceptable travel range for brake chambers listed. The travel varies depending on if the slack adjuster was moved by hand (making acceptable travel less) or if it was moved by the application of the coach brakes (making the acceptable travel greater).

2″ is not an acceptable blanket statement because acceptable limits are proportional to brake chamber size, but there is one constant. All brake chambers, regardless of size have a red band that is only visible when the chamber stroke is at the maximum and if the band is visible when the brakes are applied the brakes are out of adjustment and the coach is not road worthy.

The industry is in lock step on one topic and that is regarding automatic slack adjusters. Automatic slack adjusters are not to be adjusted by hand. Every publication I have read on automatic slack adjusters is very clear on this prohibition. If the automatic slack adjusters have to be backed off, such as when replacing pads or doing service on brakes, then the appropriate way to restore them to the proper adjustment is to make multiple brake applications until they are adjusted, or an easy way is to disconnect the air line to the brakes and introduce air into the brake chamber repeatedly with shop air until they adjust themselves. If they fail to adjust they need to be replaced or if they fail to adjust to the specified acceptable stroke length they need to be replaced.

[Gerald]

Jon is 100%correct. To clarify what I was speaking of : When some grease gets many years old it gets hard. It keeps auto slack adjusters from working. If yours has quit working this may be a place to look. I got problem on the 89(a previous coach) from a previous owner who did not grease at all and what was there was like tar. I forced this old goo out and the adjusters operated correctly. Correct maintance is the key on your coach….. If you do that problem will never happen. When I see a older coach with brake problems it is always one thing that I share. Bob

[Gerald]

Thanks

[Archived]

And I agree with Bob about grease getting so stiff it actually impedes the operation of the slack adjusters. I am not an advocate of pumping grease into fittings until it oozes onto the floor, but unmaintained slack adjusters are not going to be affected if over greased.

One word of caution. The early style front and tag disc brakes have grease fittings on the slack adjuster shaft. DO NOT OVER GREASE THOSE. What Bob is talking about is the slack adjuster itself. If the shaft fittings are given more than a dab of grease it could cause the calipers to not retract resulting in a hung brake. That is one thing to check for with the IR gun and if there is heat at the hubs that is one possible cause.

[Archived]

I paid a heavy price for just that, over greased calipers on the steer and tag, heated front rotors causing perfectly good rotors to become scrap. The shop that did it in FL offered no help. I grease my own or will be up close and personal with anyone else doing the greasing.

[glen]

Thanks guys I need to make my post more clear. I was talking about the center bearings/greased- in the slack adjusters their selves. Sometimes I have a hard time putting things into words. I need to work on that. Bob

[AL]

Bob, you were clear in what you said. We just wanted to be sure for those who may not have been aware that over greasing the shaft could have serious consequences.