Knorr-Bremse issues warning on cheaper brake units

By: Steve Skinner, Photography by: Steve Skinner

Brake systems manufacturer Knorr-Bremse says actuators not made in the US or Europe may not meet performance standards.

Knorr-Bremse issues warning on cheaper brake units
Mixing brands across an axle group has a significant impact on a vehicle's braking ability, David Oliver says.


A leading brake systems supplier is warning operators to ensure they have compatible foundation brake units on their trailers.

Knorr-Bremse, which also owns the Bendix brand, says the result of incompatible actuators could be a trailer "diving off" to the wrong side of the road.

The actuator is the front "spring brake" section of a traditional air brake chamber, which performs the service brake role (the rear section of the chamber operates the parking brake).

"Different brands, different manufacturers have different output force," Knorr-Bremse Australia sales engineer David Oliver says.

However he notes that because North American and European actuators have to meet performance standards, their braking force is roughly the same – within 5 per cent of each other in the case of US equipment.

"What we're seeing is that mixing brands across an axle group has significant impact on the actual braking ability of that vehicle," Oliver says.

"In fact, I suggest where we take non-North American or non-European certified spring brakes and put them onto an existing trailer, it could possibly put it outside the ADR's [Australian Design Rules] and maybe require re-testing.

"The problem I came across recently is where non-North American branded actuators were on an axle ... and the result was an immediate drop in the compatibility rate and we noticed a huge difference in the actual balance across that axle group.

"The number three axle which had these non-US brand spring brakes on it was doing very little work.

"Fortunately the US usually within a couple of per cent of each other as far as output force is concerned, but the stuff that's not made in the US or Europe can be all over the place, and we can see up to 20 per cent difference in output force for a spring brake that's labelled 24/30 or 30/30.

"It becomes a severe stability issue."

Oliver was speaking at the recent Commercial Vehicle Engineering and Technical Conference (Comvec) in Brisbane.

Comvec is organised by the Commercial Vehicle Industry Association of Queensland (CVIAQ). CVIAQ technical and regulatory manager John Samson supported Oliver’s comments.

"All brake actuators are not created equal and we're starting to see some issues out there with actuators of an equivalent size but the results are not the same," Samson says.

"And if you get imbalance across an axle it can certainly create some issues.

"A good practice is like for like when you're replacing. Don't just put a 30/30 on it, put the brand of 30/30 that's on the other side of the axle rather than mixing and matching."

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