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WHEN TO CHANGE BRAKE CHAMBERS?
Prevost used to say, and still may recommend changing brake chambers every year or 100,000 miles whichever comes first. That was written in their shop manual.
Nobody does that. Including Prevost near as I can tell.
But having had almost everything fail on my coaches at one time or another I created service life limits for stuff on my coaches. I change air bags every ten years. I used to change brake chambers every five, but I now have the Bremse-Knorr (or is it Knorr-Bremse?) calipers with their unique brake chamber design and I am thinking of replacing them next year at 10 years of age.
I settled on 5 years because I had a brake chamber diaphragm fail just prior to the chamber reaching its 10th birthday. But those were the more commonly found brake chambers that were of the type often sold out of bins on the parts store floor. Now my brake chambers are unlikely to be found in stock at the truck parts place because they are not typical. Has anyone had a brake chamber failure, and on what type of brake chamber, and if known what was its age?
Maybe through anecdotal evidence we can establish a reasonable preventive maintenance program life span for brake chambers.
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9 Replies
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Hopefully, my experience in my Class A coach will be relevant. I replaced both original rear brake chambers on my non-tag axle 1997 American Eagle / Spartan Mountain Master chassis at 15 years of age as ONE of the “3030 Regular Stroke” chamber’s interal diaphram had failed causing my parking brakes to not reliably release. Found the leak by airing-up completely, then shutting off engine and listening for leaks at the rear chambers. Could not hear the leak with the engine running, but it was easily identified with the engine off as the volume of air leaking when the parking brake knob was released (and wheels chocked) was loud. The replacement chamber’s were purchased at NAPA Auto Parts for approximately $80 each, if I recall accurately.
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I should have included the fact both front brake chambers are original.
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I had one fail on the drive axle in February 2012 so it was 17 years old. As I have detailed on here before it was probably in the failing process when I bought the bus in March 2008 but I did not know enought to know it. All the others were changed in 2014 at 19 years old and about 270,000 miles.
I do plan on that being the normal change interval of course and I am interested in knowing what the consensus is on it.
Davy
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Maybe I should be more specific. The ones I am questioning are the Knorr-Bremse chambers on coaches with all disk brakes.
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I noticed your reference to the specific brake chamber in your original post but I was answering this. Emphasis mine.
Has anyone had a brake chamber failure, and on what type of brake chamber, and if known what was its age?
Maybe through anecdotal evidence we can establish a reasonable preventive maintenance program life span for brake chambers.
My bad.
Davy
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No apologies because your experience is a data point for all who have the more conventional brake chambers.
I’ll add that the rubber diaphragms age differently and while some may go for 15 years or more, some may not last much beyond 5 years. I have seen some that cracked and tore due to hardening of the rubber from age, but I have also seen them fail through wear as a result of the round plate they push against rusting, and the rough surface wore a hole through the diaphragm.
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Another thing that happens is the spring inside can break. Then you have little or no holding force for your parking brake on that wheel. We saw that alot on trucks, and there was no magic mileage or age that we ever could determine when the failure occured.
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Good point and unfortunately the only way to find out the spring broke is to expect the brake to hold on a hill, and to find out it will not.
My driveway is my spring brake check. But apart from the driveway I really do not have any good place or way to check the springs except perhaps when parked on a slope to apply the emergency / parking brake while remaiining in the seat ready to apply the service brakes if required.
Some coaches, such as very early XL coaches have spring brakes on the drive axle only. Those are barely adequate. My 1987 coach would barely hold on the slope of my driveway. When the spring broke on one of the brake chambers the coach wouldn’t hold on the slope at all. Later model coaches had spring brakes on both the drive and tag axles and they held the coach well on the driveway.
A broken spring is not a big deal where the terrain is flat. After all, as long as the coach stays in one spot all is good, right? No…..the spring brakes are our last resort. If we have a catastrophic failure in our air system those spring brakes are the only thing we have left to stop our coaches. It is extremely rare when any of us is at the point where we have only the spring brakes to bring our coach to a stop, but like any other safety device we need it when we need it.
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I replace chambers every five years and hoses at ten or when they show wear or cracking both types you maybe able to just replace the back ones with park brake at five and front ones at ten years this is what I do , cheap way to be safe
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