Keeping brakes compatible

By: Steve Skinner

There will soon be plenty of guidance for getting the best out of not only foundation brakes, but the much more complicated electronic systems as well

Keeping brakes compatible
Knorr-Bremse Electronic Stability Program includes rollover mitigation.


Chris Loose reckons English is a second language for a lot of engineers.

And that’s why Loose and numerous other technical experts who have been working on a guide to braking and stability performance for heavy combinations, are trying to keep it simple.

"We don’t want to overcomplicate it," says Loose, senior engineering advisor with the Australian Trucking Association. "Every operator who tries to read an engineering book won’t go past the title.

"We made it is as easy to understand as possible. An operator will focus on three key tables, and that’s probably all he’s going to have time for"

Those three tables are in the draft document which still needs real-world testing by operators.

The tables involve ratings across four classes of brake systems and three types of braking conditions.

The first class of brake system is what are called "dumb" brake systems, which are air only. The second type is load sensing valve brake systems, which are mechanical and air. The third is anti-lock brake system (ABS); and the fourth – and smartest – is electronic stability control.

These systems are rated against light or "normal" braking; heavy or "harsh" braking; and cornering or roll stability.

Smart truck and dumb trailers

The truck might have stability control, and the trailer might have TEBS (trailer electronic braking system) with roll stability, which would give the combination the top rating for both braking and roll stability.

But if the operator doesn’t plug in the power, it’s a dumb trailer.

Loose adds that with longer combinations you have to make sure the power goes right down to the back end -- at least 9 or 10 volts at the last control unit. "Without electrical grunt it’s (also) a dumb trailer."

And don’t try to stick a 24 volt lead into a 12 volt ABS system: "That will blow it up."

The tables apply equally to trailers attached by both fifth wheels or drawbars. However truck and dogs are inherently more unstable than semitrailers or B doubles.

Semis are connected by the fifth wheel, and are therefore roll-coupled. "A truck and trailer will tend to roll together," says Loose. "There is a link, so stability system on one of those units will help understand what’s going on with the other unit.

"With drawbar units though, between a dog trailer and a rigid or another trailer, they’re not roll-coupled, so one can roll independently of the other."

Loose adds that there are lots of different warning signs that there’s a brake compatibility problem, for example uneven brake wear; different brake temperatures; and wear on the kingpin.

Solid foundations

Chris Loose says fleets should try and standardise their brake technologies, because they are often mixing and matching trucks and trailers.

That advice applies both to the electronic overlay systems as well as the foundation brake systems themselves.

Re foundation brakes: "If you have got disc brakes on the truck, put disc brakes on the trailer. Get the foundations to match. It just makes life easier."

While on the subject of foundation brakes, the ATA has just released a 15-page technical advisory procedure on slack adjuster setup and compliance to the new National Heavy Vehicle Inspection Manual.

Meanwhile in May the ATA released the second edition of its 24-page technical advisory on ESC and the similar RSC (roll stability control).

Check out the full feature on Chris Loose’s address to this year’s Comvec conference in the next issue of Owner//Driver. Subscribe here.



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