ive got a problem with a 30 ft skelly it keeps chewing through rear axle brake pads its on bpw discs its trashed 2 sets of discs and pads in less than 20 weeks ,there not getting overly hot its had new pads discs chambers and carriers it passes it brake test its not dragging or locking up the pressure from the load sensing valve is ok am not over braking or riding the brakes, I can see a reflection of my rear unit lights on the trailer and the brakes aren’t coming on on there own its not affecting the other axles and the bearing are ok and ive still got problems anyone had anything similar happen am at a loss with the dam thing
lee mat:
ive got a problem with a 30 ft skelly it keeps chewing through rear axle brake pads its on bpw discs its trashed 2 sets of discs and pads in less than 20 weeks ,there not getting overly hot its had new pads discs chambers and carriers it passes it brake test its not dragging or locking up the pressure from the load sensing valve is ok am not over braking or riding the brakes, I can see a reflection of my rear unit lights on the trailer and the brakes aren’t coming on on there own its not affecting the other axles and the bearing are ok and ive still got problems anyone had anything similar happen am at a loss with the dam thing
‘Carriers’ do you mean calipers? Does the rear axle have the correct size brake chambers fitted?
New calipers and pad carriers I think there called, chewed them up with both old and then again with replaced parts not even done doing big mileage or constant heavy work originally new pads where fitted within eight weeks it had gone straight through the pads a knackered the discs . And then did it again in a similar time after rebuilding it .
Take it other trailers are fine with the same unit?
I would look carefully at what friction material is being fitted. Are they genuine pads? Not all brake pads are the same and there is some low quality stuff out there. You got a part number of the box?
I agree, have you fitted genuine bpw parts? Something is very wrong if it’s going through pads in 8 weeks.
Done it with both genuine and spurious parts fitted your right something is very wrong just haven’t got a clue what.
Is the unit actually braking,just a thought.Had a similar problem when Merc first introduced the Actros then found out Merc had designed the ECU to
operate with disc brake trailers and insufficient adjustment was available on the ECU to marry disc brake unit with drum brake trailer.Great fun,then
a jacknife and a nice cheque from MB,then it was sorted with a redesigned ECU.
That’s what I was thinking but am getting 8 bar at the chambers on the unit and again it passes its brake test but with it been the trailer back axle only am wondering if its doing all the work effectively holding it all back but I would expect it to be getting overly hot which it ain’t
You are either over braking on the rearmost axle or it is binding.
There should be an information plate on the trailer chassis from Haldex, wabco etc relating to the LSV with details of airbag pressures unladen and laden and also the brake chamber pressure laden and unladen. This will be for a given input pressure in the yellow line. You have to start somewhere investigating this so compare what you are getting with what is on the plate.
You have also mentioned that the RBT figures are OK, but is this tested at nearly full axle weight or on locks for an empty tri axle? ie are the other axle brakes effective?
After you apply the service brake when you release is the air evacuating quickly. I would lean towards something like the pads aren’t releasing from the disc quickly enough. I don’t think it’ll be the calipers if they’re both affected. Or, it could be, as mentioned the wrong chambers. Meritor axles used to need spacers for some chambers but don’t think I’ve come across anything like that on BPW.
I agree, don’t think a pass on locks brake test is going to tell you much other than if it’s got a bad bind.
Is there anything slightly unusual about this trailer other than it is only 30ft long? does it for instance have a lift axle or does the rearmost axle steer? Do you do a lot of your loaded running with the tractor mid axle lifted and when this is raised does the fifth wheel height increase?
Its just a bog standard 30ft tank skelly no lifts axles .the brakes don’t appear to be holding on we jacked it up on the pit then spun the wheels and kept pressing the brakes to see if they where holding on but where ok .its not an obvious fault and I don’t think its going to be found in the garage but somethings not working right whilst its on the move .
Dragging this from way back when I had Merc probs.Check braking required 1.5 bar,stopping took 6 bar and that is with discs, you say your getting 8 bar
not too much to be done to ease of the pressure to the trailer,30 seconds with unit plugged to computor.But if you drove unit and empty trailer about
200 yards and applied brakes with a buddy watching you might get a clue as to what is actually happening.
This is all t hat we went through over weeks when MB claimed there was no fault.Good luck, it does your head in I know.
Check the predominance setting on the tractor unit by putting a gauge on the front chamber of the tractor and a gauge on the rear trailer axle chamber and slowly press brake pedal. The trailer pressure should be 0.3 to 0.4 bar higher than the tractor unit, any higher and the trailer will be doing too much of the braking, causing your problem.
Just a thought, its not binding after handbrake release is it? Had this caused by blocked in-line filters ,. On tanker work with shifting load and constant check braking 8 weeks is not unheard of, but don’t think its normal for skelly operation. Think you need to get it loaded and carry out a full air pressure check, unit and trailer combined.
lee mat:
Its just a bog standard 30ft tank skelly no lifts axles .the brakes don’t appear to be holding on we jacked it up on the pit then spun the wheels and kept pressing the brakes to see if they where holding on but where ok .its not an obvious fault and I don’t think its going to be found in the garage but somethings not working right whilst its on the move .
I think the only thing you are going to prove on the road is that the brake disc temperatures are higher for the affected axle. If you check with an infra red thermometer at least you will know by how much and whether there is any significant increase in temperature from simply rolling and coasting to a halt.
lee mat:
ive got a problem with a 30 ft skelly it keeps chewing through rear axle brake pads its on bpw discs its trashed 2 sets of discs and pads in less than 20 weeks ,there not getting overly hot its had new pads discs chambers and carriers it passes it brake test its not dragging or locking up the pressure from the load sensing valve is ok am not over braking or riding the brakes, I can see a reflection of my rear unit lights on the trailer and the brakes aren’t coming on on there own its not affecting the other axles and the bearing are ok and ive still got problems anyone had anything similar happen am at a loss with the dam thing
buy an infrared thermometer loads on ebay etc to see disc surface temp if its running excessively hot it will melt the caliper bellows the only trailers ive seen go thru friction at that rate under normal running are timber trailers lol. At your rate of wear the brakes should be stinking hot and the bearing grease turns to black runny puss.Check the temperature of the brake surfaces on the whole rig .
It is possible that this trailer may have a pressure reducing valve in the service supply line to axle 3 brake chambers. It may well look like a quick release valve. If this has failed 1 to 1 then the axle will be overbraked. There will be test points on axle 3 and another axle if one is fitted.