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DRIVING/TOWING - 4WD DRIVING SKILLS

UNDERSTANDING ELECTRONIC/ELECTRIC HANDBRAKES
Complication in the interests of greater safety.

 

Increasingly, electronic/electric parking brakes are being fitted to new wagons and utes. And some of them apply and release automatically. Do you know how to use one correctly?

 

The first type of vehicle brake was a lever acting on wooden block, pressing on the rear wheel rims cart being pulled by a horse. Back in our youth, some of us had similar brake levers on billy-carts! 

The horse and cart braking system was employed by early motoring pioneers, including Bertha Benz, who slowed her husband’s Motorwagen by pulling a lever that pressed blocks of leather directly against the rear wheels.

When braking systems developed to internally expanding drums, operated by foot pedal, the lever brake became a parking brake and also an emergency back-up if the cable or hydraulic actuating system gave up.

 

 

Late-20th century vehicles had split-circuit braking systems that largely eliminated total brake failure, so the handbrake became mainly a parking brake in real-world practice.

However, skilled rally-car drivers used handbrakes to good effect in creating wanted tail-out attitude in tight corners and 4WDers could use careful hand-braking to control errant rear wheel spin, to some extent.

When electrically-controlled braking systems became commonplace, it was only a matter time before engineers employed electronics in hand-brake systems in cars and then 4WDs, including utes. Electronics were used to program the braking action and electric motors replaced the manual ‘pull’ on the handbrake lever.

Electronic control also allowed the engineers to integrate parking brake action with foot brake action and make the parking brake a last-ditch, emergency brake in the event of normal brake system failure.

Most drivers don’t read vehicle operating manuals, because they’re too thick, but if they did they’d most likely see a section that explains the use of the parking brake ‘flap’ control as an emergency brake.

 

 

We’ve witnessed a test driver pull on an electronic/electric parking brake at 180km/h and watched the vehicle come to a controlled, if somewhat gradual stop. The rear brakes were overheated and in need of a rebuild, but the ‘emergency’ was avoided. 

Early electronic/electric brakes in utes were actuated by a small flap control, usually on the centre console. When the driver pulled up and engaged ‘P’, a message would appear on the dashboard, telling the driver to engage the parking brake.

To release the brake, the driver could simply drive off and the brake would release automatically, or push or lift the flap. However, later vehicles have fully autonomous parking brakes that also apply automatically when the driver engages ‘P’ and release when the vehicle moves off.

Obviously, these modern handbrakes do not have the ability to work for hand-brake rally turns, or as a poor man’s diff lock.

 

Outback issues

We had an electronic/electric handbrake on our Land Rover Discovery, years ago and absolutely hated it. Because it was integrated with the vehicle’s emergency braking system it couldn’t be adjusted without the aid of a computer!

It stuck in the engaged position several times and on one occasion we had to drive off with it locked on, tearing the linings off the shoes.

Hopefully, since those early days, the product quality and functionality has improved, but we still think it’s a very high price to pay for emergency brake backup, when there’s already dual-circuit braking that just doesn’t fail, these days.

We think the real reason designers have gone down the electronic/electric parking brake route is to make it easier to locate the ‘handle’ inside the vehicle and to make that handle more stylish. 

With a mechanical brake, you need to have a relatively linear run aft to the rear brakes, but with a switch and wiring connection that route can be circuitous.

So, what we have now is a system that relies on several electronic and electrical components, all of which need specialist servicing.  That’s much more difficult – and expensive – than dialling up the correct ‘lash’ between brake shoes and drum, and adjusting cable length to compensate for stretch in the wire over time.

Every year, modern 4WDs become less and less bush-friendly.

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