[Mark]

Are these the original pads or have they been replaced?

[joel]

Has Prevost been made aware of this???????

I think this goes beyond just the fronts. It might be isolated to coaches with Knorr Bremse brakes or more widespread. Any members that find the problem please report here and be specific as to model year and type of coach.

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1999 XLV X-6872,  liberty #440

[Loc]

Tom,

How many miles do you think are on these brake pads?

Mark

[Mark]

Although I am not a brake pad expert (YMMV), I would suspect overheating as opposed to defective brake pad material. I’ve pulled similar pads off my race track car.

Were any problems noted with the disc and/or were the caliper pins free? I would expect fairly heavy disc wear.

[Archived]

Joe I thought the very same thing. I see that on the race car from time to time too. Maybe the coach problem is caused by heat like we think is caused in the race car, maybe it isn’t.

Joe, do you use different brands of pads on the race car? I wonder if there is a difference. That could be an issue with the coach pads. Bad batch?

Someone out there is a brake pad expert.

[admin]

No idea if these are original, 82K miles at present. I’ve seen two here at ETLC and they see it on a regular basis. Rotor’s look perfect and no other signs of wear, I assume it’s heat related by previous owner’s.

[Archived]

Maybe I am overly concerned, but if there is a pattern of this type of brake pad deterioration this represents what could be a serious safety issue.

Regardless of the cause these pads are failing. Something is wrong. I’m no brake expert but have seen and worked on disc brakes over the years and have never seen pads that look like that. They are disassembling themselves. To try to justify what is happening by saying they got hot is ignoring the fact they are expected to get hot. Very hot. That is what happens when we use our brakes.

I think this problem is serious enough to determine its scope. Is it a problem with a specific batch, specific type of brakes, a range of model years or is it related to H models because the two I am aware of were H3 coaches.

[Archived]

Brake pads are designed to fulfill specific purposes which are compromises. Automotive brake pads for street can be designed for initial bite, sound, wear, dust, etc. My race pads will take much higher temps (abuse?) but have terrible dust and sound properties. Trade-off.

Easily possible to owner-abuse our bus brakes.

Having said this, I’d be interested in what an expert would say about these pads.

[Gerald]

Possible road salt caused it to “soften” they look like “particle board” that is left in the rain. ? just asking, I have never seen car or truck pads do that.

[Doug]

Just completed a Level 3 service at Prevost Houston. Had a LH drive hub seal leak, so checked pads while wheels were off. Same appearance as Tom’s and rotors show no evidence of surface cracks, grooving, or excess heat. We took possession of the coach in February and only have 2,000 miles on it (has 128,000 miles total), and I don’t have any history on the brakes being serviced. But from the remaining pad thickness they don’t appear to that old. Replaced these with Prevost PN 642188. Spring of 2020, I’m changing out all the bellows so will recheck all pad/rotors/calipers then.

[Archived]

We were just at ETLC also and our front brake pads were just changed as they looked the same. Jeff said they have been seeing a lot of front pads look this way lately.

[Ed]

The difference in braking now with new pads is remarkable, helps having the entire brake pad surface working.

[Archived]

Had front pads replaced at Prevost Dallas in April. Pads on Tag and Front Axle were at 40% life. 1999 XL with 252,000 miles. Coach has been highway driven since day one. Second owner kept every record since purchase at 140K miles. No record of front brake pads ever being replaced. They did not need to be replace…but it was my request since bus was already on lift for another brake issue.

The caliper pin boots were worn and had holes at 252K miles. Replacing the boots and sanding the rust off pins before they caused real problems started the adventure.

So here are my pictures. I sure wish I did not have my mothers depression era pack rat tendencies to save everything. But I keep every part coming off the bus. Pads all in good shape. Bus is highway miles no stop and go, abrupt stops, riding the brakes, or etc….

[Archived]

I had the opportunity yesterday to show Tom’s picture to a brake expert. He took one look and confidently replied, “Heat.”

He said that the center deterioration especially points to heat. Extreme thermal expansion causes the pad material to fail in this way. He said it’s more common to see this around the edges where there isn’t surrounding material to dissipate the heat energy from the contact surface. (Similar to welding the edge of a piece of metal.) The damage in the center of the friction material is clear evidence of overheating events.

He has extensive experience with brake control systems, worked for a Tier-1 brake supplier, and now does expert testimony, teaches, and races.

[Archived]

My Meritor disc brakes have Meritor Helper Springs installed on all slide pins. The helper springs force the pads away from the rotor when the brakes are released.