AIR BRAKE CHAMBER KNOWLEDGE

wayne · October 18, 2011, 10:07:30 AM

Does anyone have extreme knowledge of air brake systems from Bendix or MGM? I have a 1990 Setra 215. I matched up the tag axle brake chambers but the drive axle has a spring chamber with a crossover tube. Not sure what the tube is for, maybe a vent. The chamber is aluminum with Bendix & MGM cast in it. It looks like a type30/30. I talked with bendix and was told they never did anything with MGM. I talked with MGM and was told they never did anything with Bendix. After I sent a picture they said maybe they did but there is no info on it and it must be obselete.

belfert · October 18, 2011, 10:47:59 AM

Can't the service brake side be replaced separate from the spring brake side? What are the chances someone replaced one side with a different brand name?

bevans6 · October 18, 2011, 11:29:57 AM

Can you post the picture you took? Where does the cross-over tube start and finish?

Brian

luvrbus · October 18, 2011, 12:04:37 PM

Could be somebody replaced the chambers on a Bendix housing both the Haldex and MGM will work on a Bendix housing

good luck

Joe Camper · October 18, 2011, 12:38:38 PM

I know what your talking about. You are referring to a crossover from the emergency chamber to the service chamber on the same maxi I think. Right

Those 2 small holes that the tube connects are vent holes on the backside of the diaphragms so that positive pressure is not created when the diaphragm is pressurized.

Not all maxis have this crossover because it is not really necessary. It is an afterthought in an attempt to keep out dirt and grime and limit corrosion.

bevans6 · October 18, 2011, 12:44:21 PM

There was a long conversation recently about Maxi chambers, how expensive they are and how they can be replaced with normal spring brake chambers. If that's what this turns out to be.

Brian

wayne · October 18, 2011, 12:48:35 PM

The words "BENDIX" AND "MGM" are cast on the same housing. I think Joe is right about it being just a vent tube, so does that mean I can replace it with a type 30/30.

Joe Camper · October 18, 2011, 12:51:16 PM

I can get 30/30s for 45 bucks a piece. prevo uses 16/24s on the tag those are pricey even more than 30/36s that are 175 a piece and you see on many bus drive axles.

Ususally I see folks with older stuff upgrading to maxis not the other way around.

Joe Camper · October 18, 2011, 12:59:36 PM

1 question is there a tag axle and if so are there maxis on that axle too?

If so 30/30s are good. If however you have a 3 axle bus with only 1 axle with maxis you should use the 30/36.

I can tell you from personal experience owning a bus with only 1 axle with maxis (parking brakes) I have encountered this.

.... if you are not right on top of the brake adjustments you will know it because when they get out of adjustment a bit too much and you are on unlevel pavement the buss will still roll after the parking brake is set. And that's with 30/36s so you can assume the situation would be even worse with the 30/30s.

wayne · October 18, 2011, 02:02:00 PM

I'm getting a little confused, I thought 30/30's were a maxi. I better read up a little more before I continue.

prevosman · October 18, 2011, 02:37:25 PM

Quote from: wayne on October 18, 2011, 10:07:30 AM
Does anyone have extreme knowledge of air brake systems from Bendix or MGM? I have a 1990 Setra 215. I matched up the tag axle brake chambers but the drive axle has a spring chamber with a crossover tube. Not sure what the tube is for, maybe a vent. The chamber is aluminum with Bendix & MGM cast in it. It looks like a type30/30. I talked with bendix and was told they never did anything with MGM. I talked with MGM and was told they never did anything with Bendix. After I sent a picture they said maybe they did but there is no info on it and it must be obselete.

The crossover tube is not important because it does not impact how the brake chamber functions. I think you are describing a spring brake parking or emergency brake coupled with a service brake. Let's presume it is a 30/30 which is common. If you get one with the same stroke you should be good to go.

I cannot explain why you see Bendix and MGM cast on the unit. Just take your old one to your local purveyor of brake chambers and they likely can sell you a new one, matching the stroke you have. 30/30 mis not an oddball. If you had an oddball such as the 16/24 mentioned previously it might have been built from a piggyback which might have used the spring brake section from one manufacturer, and the service brake section from another.

Joe Camper · October 18, 2011, 05:05:44 PM

Sorry to confuse you. Yes 30/30 are maxis.

thunderstruck · October 18, 2011, 05:17:09 PM

30/30's are the most common and should run about $100 each. probably the reason you see two brand names is the outter parking brake chambers were replaced at some point. I just replaced two 30/36's and they cost me $130 each...

Joe Camper · October 19, 2011, 03:18:47 AM

Where did you get 30/36s for 130 bucks that is a good price on those

Or possibly that was for a "piggyback" and not the entire thing.

buswarrior · October 19, 2011, 05:32:23 AM

Hello Wayne.

The discussion so far is pretty good.

Sounds like you may go shopping for a relatively inexpensive replacement.

Do be sure that you have no space issues with the shape of your current chamber and the replacement. Some coaches (besides the MCI and DD3) have clearance issues, and chose the particular, and often rare, chamber to solve a packaging problem.

Joe Camper's suggestion to upgrade to a bigger parking portion if you only have spring brakes on the drive is worthy of consideration. The newer coaches are coming from the factory with a lot more parking/emergency braking strength than your 1990 has.

And, if space permits, consider an upgrade to long stroke chambers. That will give a busnut more stroke to defend against the loose brake adjustment creep as described above by Joe Camper.

happy coaching!
buswarrior