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hdfx81

self adjusting brakes

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Interesting discussion! I've never driven or seen a big truck with disc brakes! I figured they were either too expensive or unreliable so never became popular! From what Heavy Gunner says they wear out pads in the same order as hydraulic disk pads (piston side first to wear out), makes sense in both cases as the piston side contacts the rotor  first and gets a little extra wear before the other pad contacts the rotor!  On self adjusting  drum brakes I  have never,not once ever seen a brake that wouldn't take some adjusting! Turn the adjusting nut in till the brakes lock, then back it off 1/4 turn then grab the linings and shake them to make sure they aren't binding and you're done! Of course visually check all the visible components. I always did this before I crossed into California! You could feel the difference in braking after this procedure! The brakes may have been legal without adjustment, but not necessarily equal. When you adjust them they are all equal! As far as the newbies go the vast majority aren't gearheads and have little knowledge of anything mechanical! They got into trucking  because it was the only job that paid a " living wage" without college,and In many cases with college! At least half of them couldn't even drive a stick tranny when they went for training! You don't even have to parallel park a car in Florida to "qualify" for a drivers license. The majority won't last a year, because you have to love trucking to be able to tolerate the ever increasing corporate and regulatory bullshit that it entails! In the meantime God help the motoring public! By the way one of the three tragically killed wrecker drivers in Florida this year was killed by an 18 wheeler! The other  two were killed by drunk drivers!

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1 hour ago, gearhead204 said:

we had one rd 688 late 80's or early 90's that had disc brakes, we couldn't find pads locally  so we changed it over to shoes and drums from a wrecked truck. so I didn't get to play with them much.

 

The early disc brakes had a can a arm/lever style, the new Bendix or Meritor ones are direct acting with an air piston. Like day and night. I have the old style Bendix on my '92 Marmon, makes a difference OTR and replacing all the pads on 3 axles isn't a big job.Replaced 3 calipers and one Anti Skid Sensor in 22 years.  The newest are the same design as railcars use.   Paul

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It only makes sense that disc brakes on ANY  vehicle assuming they are sufficient square footage ( pad and rotor surface ) and properly retrofitted, or factory installed for the gvw of the vehicle will stop better and last longer due mostly to better cooling! Of course they are by nature self adjusting and self cleaning! And remember 99.9 percent of those trailer brakes you see smoking at the bottom of Monteagle and the grapevine are drum brakes! I actually saw a tractor catch on fire at the bottom of Monteagle and burn to the ground from hot brakes! And while it is a downgrade that deserves your respect it's not even close to the worst one! BC, I'm not surprised that the bus fleets are utilizing disc brakes due to the value of their cargo and their litigious nature 😁 The cargo that is lol As far as the big truckload fleets are concerned most can't see past initial cost at least in America! Plus until they become (the standard) parts availability could be dicey,as some of the members have noted.

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41 I was a freight car repairman until 1981.Up to that point the rail cars used sort of a disc brake deal where the brake shoes grabbed the outside of the steel wheel! Almost like a disc, self cleaning and out in the air stream for cooling. Actuated by a long linkage rod to a giant air tank under the car! Almost like the pre maxi air operated emergency brake system on the old truck trailers. Have they come up with a new disc brake system,or are you referring to the system I described?

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6 minutes ago, BillyT said:

41 I was a freight car repairman until 1981.Up to that point the rail cars used sort of a disc brake deal where the brake shoes grabbed the outside of the steel wheel! Almost like a disc, self cleaning and out in the air stream for cooling. Actuated by a long linkage rod to a giant air tank under the car! Almost like the pre maxi air operated emergency brake system on the old truck trailers. Have they come up with a new disc brake system,or are you referring to the system I described?

It is a new system designed by Bendix-Spicer, Fuji Heavy Industries and Rockwell International. It was originally designed for the ACELA and the Japanese Bullet Trains. Found it works great on freights and subways. Worked it's way to trailers and trucks.

Pads are available all over now, Napa can get them.

This is for trailer conversion about 3 grand for the entire package for two axles.

hendrickson.jpg

New style Bendix same as R.R. units.

bendixairdiscbrakes_10125934.jpg

 

 

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