PARTS: Disc breaks


A device developed in Australian has been acclaimed to double brake pad life

PARTS: Disc breaks
The Ca Tec caliper support system, a bracket extending brake pad life

Disc brakes are so much better than drum brakes that no one really ever questions their performance or their reliability.

They always seem to be working well, never pulling to one side or the other and, most significantly, they have largely banished the phenomenon of brake fade on long and steep descents.

But a new Australian invention is proving to bus and truck operators that, despite their advantages, disc brakes do very often decline in performance.

It’s just that this deterioration is not as obvious as when drum brakes are performing poorly.

But declines in disc brake performance – difficult for drivers to recognise over time – have been clear to maintenance managers for a while.

They have been wrestling with uneven brake pad wear, fracturing of the rotor due to uneven temperature spread and caliper rattle for years.

All three problems stem from the same cause, excessive wear of the caliper pins and bushes, says Ca Tec Sales Manager Peter Pace, the man who inadvertently sparked the development of the new device.

The invention is a simple-looking bracket called a caliper support system. It ensures that a disc brake stays virtually at the manufacturer’s specifications for its entire working life.

"I was working at Toll Holdings in St Kilda Road [Melbourne] running a tanker fleet," Pace says.

"We had a few tankers on discs and we found that they were quite expensive to keep on the road as far as brake costs went.

"We had very short pad life and very short rotor life because they were cracking. On a fuel tanker, as soon as you see cracks you change them out straight away."

In fact, he had decided to switch back to drum brakes when he had a chance discussion with inventor and engineer Martin James.

After months of brainstorming, James finally came up with a bracket that better supported the disc brake caliper in relation to the brake rotor, and stopped it leaning over because of uneven wear on the pins and bushes.

James recognised that, with the brake booster fitted to the caliper, around 80 per cent of the weight of the caliper assembly was on one side of the rotor and only 20 per cent on the other.

This led to rapid wear of the two pins and bushes that hold the caliper in place, leading eventually to a misalignment of the caliper to the rotor. 

All the problems stem from this, Pace says.

"At Toll, we basically doubled the pad life with Martin’s unit and quadrupled the rotor life. Because we could stop the cracking, we actually got to wear the rotors out rather than throw them out prematurely."

Pace says the Ca Tec bracket adds at least one extra mounting point for the caliper, most often two. These have sliding pins, too, but while the brake manufacturers use a tolerance of 0.5mm on their pins, Ca Tec has just moved to a tolerance of 0.2mm.

Ca Tec can do this because its pins are located relatively far away from the intense heat that builds up around the caliper.

Pace says it has taken seven years to get this far, but activity has started to spike in the last six months as the caliper support bracket works just as well on buses as on trucks and trailers.

BUS INDUSTRY SUPPORT

The Dyson Group was quick to offer a donor bus for trialing earlier this year and has already committed to fitting the caliper supports to its entire fleet, the second largest in Melbourne.

"We are gradually retrofitting them across the fleet," says Dyson Fleet Services Manager Mick Reynolds. "All new buses have them installed. 

"The crux of the whole thing is the calipers lean over, causing hot spots on the brake pads and premature wear on the pads and rotor.

"The first bus we did is up to 90,000km and the brake pad wear is not even half what we are used to. The rotor looks relatively new."

Reynolds says the bracket works just as well on old calipers as it does on new ones.

"It is looking like we are going to get double life out of brake pads and rotors, which is really big.

"That’s not including replacing the caliper if it had crook bushes. That’s another saving."

Reynolds says the benefits don’t end there, either. With the full face of the pads meeting the rotor, brake performance improves strongly, too.

"We put them on a Scania we use for V/Line services and didn’t tell the driver. Not long after, he had to pull up sharply to avoid animals on the road.

"The next time he came in he asked what we had done to the brakes. He said he had an issue where he had to stop quickly and the bus pulled up quicker."

In fact, this has been verified during extensive testing.

IMPROVED BRAKING

Simulation tests at the Bendix/FMP facility in Ballarat showed that a fully laden B-double semi-trailer fitted with the Ca Tec bracket and travelling at 100km/h would stop in a distance of 110m, more than 16m less than the same vehicle with no Ca Tec brackets.

The tests were done at three different speeds and four different running temperatures and the brakes with the bracket were better in every single test: improved braking torque, decreased temperature variation on the rotor and average temperature.

Pace says some bus chassis manufacturers have started, or are about to start, testing the Ca Tec caliper support. One company is testing it at its European base.

While retrofitting the bracket to all the buses on the road in Australia would be a big job, Pace and his partners in the sales company, Ca Tec Sales, are hoping for bigger things.

"We kept it separate from the manufacturing company because one day we might need a big marketing mob to take it over. That’s good.

"We are here at the moment trying to get it going and see how it works out.

"We are hoping that it may go to Europe, end up in Europe and all over.

"If it does, it’ll be bigger than we can manage."

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