Should I change auto slacks to manual?

belfert · August 31, 2011, 07:08:57 AM

I have auto slack adjusters and it appears the front ones are probably bad. I don't want to keep replacing these things at $134 each. If the bus sits a lot would I be better off with manual ones? Would it even be legal to switch to manual slack adjusters since mine is a 1995 and I think this is after auto slack adjusters were mandated on air braked vehicles.

Everything is in adjustment now, but my understanding is if you have to manually adjust auto slacks they should be replaced.

luvrbus · August 31, 2011, 07:19:24 AM

Depending on the s cam shaft splines you may not have a choice with the adjusters

good luck

lostagain · August 31, 2011, 08:28:45 AM

I just replaced my front ones with manuals. I like them better. The slack is only 3/4", compared to 1 3/4" with the autos.

I heard you're supposed to adjust the manuals once in a while, LOL.

JC

Busted Knuckle · August 31, 2011, 08:42:01 AM

Brian Clifford is correct.
If they didn't have an option of both available you probably won't find any to fit your S cams shaft.

You could have the S cam shaft replaced to ones that manual slack adjusters would fit on. But that is a lot of expense !

I'd make sure that the ones you have are properly installed and have the bracket that makes them adjust positioned correctly! (biggest problem I've found w/autos is people don't have this done!)

If they are indeed bad I'd grease adjust them before your trip out west. Then once you get there check and see if they are out of adjustment again. (a Dina is easy since they sit up good and don't have bags to go down on you. Plus of you turn the wheel you can reach it without getting under it.!)

If they are pretty much the same or close to what they were before the trip I'd just keep 'em and adjust them before each trip! (ain't like you drive it a lot!)

BK

buswarrior · August 31, 2011, 09:01:41 AM

Back up the bus...

Brian, what makes you think they are bad?

JC, what was the adjustment limit for that brake, and were the autos set-up properly?

There is so much time and money WA$TED changing automatic slack adjusters that are fine, and too many people claiming to know what they are doing with them who DO NOT.

An automatic slack adjuster can best be thought of as a ratcheting device. When the lever moves past the ratcheting point, it advances the mechanism so the lever doesn't have to travel as far the next time. This compensates for brake lining wear.

The trick is knowing how to set this point of adjustment correctly, and that can be VERY different between manufacturers as well as between a given manufacturer's models.

This is yet another time when parts identification and proper procedures, as detailed in the manufacturers written directions, should be followed.

But there's more money in selling new parts...

happy coaching!
buswarrior

belfert · August 31, 2011, 09:51:07 AM

Quote from: buswarrior on August 31, 2011, 09:01:41 AM
Back up the bus...

Brian, what makes you think they are bad?

Something happened to the front brakes and the brakes were not braking evenly. The shop looked at them and adjusted them, and said I just need to drive the vehicle now and see if problems crop up again. They said the slack adjusters would likely need replacement if it happened again right away. At $125 each for automatics manuals seem a lot cheaper at maybe $20 each.

The shop also checked the rear brakes and found that one of the tag axle slack adjusters is bad. It is a Haldex part, but rust has obscured the part number. They took it to four different parts places with no luck as it is somewhat unique. I ended up having to order one through MCI at 8:45 pm last night and having it overnighted. The part is at the shop now and the bus will be ready this afternoon. I didn't think to call Bryce last night to see if he could find a part number on his Dina. Maybe I could have saved the $77 shipping cost if I had a Haldex part number.

I am going to ask for the adjuster back so I can find someone who knows if it is really bad.

I thought what C&J Bus Repair was doing for me was a brake inspection, but he said all they were doing is checking the stroke and lubricating everything. He said a brake inspection takes them two hours. I might just take the bus to this new shop for brakes as they charge 25% less.

belfert · August 31, 2011, 10:10:37 AM

It wasn't until I took the bus out for a drive Monday morning that I realized there was a brake problem that seemed to be getting worse the more times I had to brake. I found a shop that could look at it Monday evening or Tuesday so I took it there and they looked at it Tuesday afternoon.

In retrospect, I should have had the brakes checked earlier and I wouldn't be getting things fixed last minute. I had assumed C&J Bus Repair was doing a full brake inspection.

Just Dallas · August 31, 2011, 10:38:20 AM

It seems to me you jumped on me for suggesting that it was up to YOU to keep a check on your buses condition. IIRC, you said something of the nature of, "That's what I pay people for".

I have no sympathy for you. You refuse to look at the bus systems, other than the engine and transmission and hope that your 'yearly inspection' is good enough. Those slack adjusters didn't go bad in a year. They probably wouldn't have gone bad in 5 years if they were lubed and checked by the owner.

My thought would be to get on your @$# and crawl under the bus, looking at any and everything and fixing any single thing that looks like it could be a problem.

A shop cannot and will not check every possible problem. You wouldn't pay for it and if they asked you to, you scream bloody murder. The shop will do exactly what you tell them to and nothing more.

Every year you go through something like this........ You complain about heat, cold, wet, dry, late, early, anything but the lack of your doing required maintenance. A shop isn't a panacea for your responsibilities. Repair shops are there to fix things..... not primarily to look for stuff that you should have found as an owner of a piece of heavy over the road equipment..

Quote from: belfert on August 31, 2011, 10:10:37 AM
It wasn't until I took the bus out for a drive Monday morning that I realized there was a brake problem that seemed to be getting worse the more times I had to brake. I found a shop that could look at it Monday evening or Tuesday so I took it there and they looked at it Tuesday afternoon.

In retrospect, I should have had the brakes checked earlier and I wouldn't be getting things fixed last minute. I had assumed C&J Bus Repair was doing a full brake inspection.

prevosman · August 31, 2011, 11:26:38 AM

Cynic that I am I would get under the bus and see how much travel the brakes have. I would not rely on someone to tell me. 1 3/4 sounds almost too much. Around 1" seems about right without looking in the book.

If the travel is too much I would disconnect the hose to the brake chamber and using shop air give repeated shots of air to see if they adjust into the proper travel range. If not, I would replace them with a set of automatics. All they need is occasional lube so once new ones that work correct are installed they should last a life time.

Hard to imagine both going to hell at the same time. If in fact both are bad it suggests someone who worked on them previously did not know what they were doing.

belfert · August 31, 2011, 12:00:10 PM

Quote from: Just Dallas on August 31, 2011, 10:38:20 AM
I have no sympathy for you. You refuse to look at the bus systems, other than the engine and transmission and hope that your 'yearly inspection' is good enough. Those slack adjusters didn't go bad in a year. They probably wouldn't have gone bad in 5 years if they were lubed and checked by the owner.

Plain and simple, I understand the principles of how air brakes work. I don't know how to tell if the brakes are in adjustment or not. I don't have anyone to teach me.

My plan right now is to go to the Bendix brake school in 2012. I don't have the time off available to go to any of the remaining classes in 2011.

I've crawled under the bus many, many times. Since I have no real idea of what things should look like I can't tell if the brakes are adjusted right or not. The drums, pads, and some of the other parts were replaced in 2006 along with all of the wheel bearings. I asked some local bus nuts at the time if I should try to fix my own brakes and they said no I should take the bus to C&J Bus Repair.

I know that I don't know how to fix air brakes which is why I have asked C&J Bus Repair every year to check the brakes for me.

bevans6 · August 31, 2011, 01:11:24 PM

Brian, it's really really simple. the brake cannister has a push rod. The measurement is how much farther out the push rod sticks when the brakes are full on vs when they are off. All you do is get your bus aired up and chocked so it can't roll. Get to where you can put a ruler up alongside the push-rod and take a measurement from the face of the can, or the mount, to the end of the rod or the clevis jam nut. Doesn't matter which as long as you remember. Then go in the bus, take a stick of suitable length and jam the brake pedal on hard. Go back under the bus and do your measurement again. The difference is the push-rod extension.

Each cannister will have a legal limit for pushrod extension. My bus manual calls out 2 1/4" for the fronts and 3" for the rear DD3's. I like to see no more than 1 1/2" on the fronts and 2" on the rears. Now that is full brake pressure, not tugging on the pushrod. It should be fairly equal side to side on each axle, but you don't need to be precise. Within a 1/4" is fine.

I hope this helps a bit.

The other Brian

prevosman · August 31, 2011, 01:45:31 PM

If it will help, if when the push rod on the brake chamber is extended such as when the brakes are applied (I just have my wife hold the brakes down for the minute or so it takes to look at them all) if the red ring is visible the limit has been reached.

A good rule of thumb is the total travel should be 1/2 of the limit which was correctly stated above by the other Brian.

Back in the good old days of non-automatic it was just a part of a chassis lube to adjust the brakes. Tighten them until they were fully applied (9/16 wrench I think was the size I used) and then back them off 1/4 to 1/3 turn. I used to spin the wheels until I knew how far to back them off without dragging. Then I just always backed them off the same amount.

Lin · August 31, 2011, 02:28:28 PM

Brian, everyone says it's easy, and it really is. However, it is possible to adjust things backwards and make it worse. I would suggest you take it to a pro now to get it adjusted. If there are no problems, it should be cheap. If there are problems, you'll get a diagnosis and estimate. Make a deal for them to let you watch and learn. As simple as it might be, you don't want to get this wrong. I have done that. Also, check Youtube. There must be videos of this available. Once you know, it's all good, keeping it there won't be a problem.

belfert · August 31, 2011, 02:38:45 PM

My concern is more about determining if I have bad brake chambers, bad slack adjusters, bad s-cams, or similiar. It would be difficult for me to tell a bad one from a good one. This is why I'm going to go to the Bendix air brake class next year even though I'll probably have to take a week off work to go.

I'm unclear why it is so much better to do this yourself instead of paying a professional? I'm guessing you guys do everything yourselves on your house, car, bus, and everything else you own. You must not go to doctors either because you should be able to do that yourself too.

Lin · August 31, 2011, 03:00:54 PM

I don't think it is necessarily better to do it yourself. If i am having something else done, I will tell them that while their at it, adjust the brakes. However, it is good to know how to do it in case you are wondering if they are in adjustment. Since you have questions about the general safety of your brakes, you should have a professional check it all out. Being able to manually adjust your brakes does not mean you are knowledgeable enough to recognize other issues. This is not an area to be guessing at. I don't see why you are putting this off.