Monday 23rd April 2018

PH Origins: Electronic parking brakes

Love them or hate them, electronic parking brakes are here to stay

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Electromechanical parking brakes offer numerous benefits - which is why, over the past several years, the number of cars fitted with them has increased dramatically.

For starters, an electronic parking brake only requires a button in the cabin. This gives the designers far more freedom, when it comes to interior design and layout, and frees up a little space. EPBs also grant a range of assistance functions, such as an auto-hold feature for automatically engaging the parking brake when stopping on hills or crawling in traffic.

Because most set-ups use actuators mounted directly to the rear brakes, no parking brake lever, pedal or connecting cables are required; this makes it easier and quicker for the manufacturer to build the car. Compared to drum-in-hat parking brake set-ups, they can also end up being lighter - granting minor emissions, economy and handling benefits.

Simplicity and safety, that said, has always been one of the key motivations behind the concept of EPBs. A system that can automatically engage a parking brake when a car's door is opened, for example, could prevent an owner having to watch their pride and joy take a short journey into a neighbouring garden.

Additionally, an EPB can automatically stop a car from rolling backwards when stopped on a slope or attempting to set off - saving an inattentive driver from an unwanted bump, or protecting a distracted driver from an incident. It was this type of event that prompted one such early concept of an automatic parking brake, with inventor Sol Seidman - based in Beverly Hills - filing a patent for 'Motor Vehicle Control' in 1927.

The idea of an automatic braking system itself wasn't new, with patents for emergency train carriage brakes dating back to the late 1800s, but Seidman's was seemingly the first to directly reference an automotive application. His patent described many mechanical revisions to make driving easier, including a system that would automatically operate the parking brake when required. Similar ideas followed, all being based on the concept of preventing unintentional rollback and making driving easier.

The Chrysler Corporation, in 1940, was also looking at ways of automatically applying the parking brake - but, primarily, as a means to stop vehicles with automatic transmissions creeping forwards when in drive. The anti-rollback function hadn't been overlooked, however, and was listed as a prominent secondary benefit. Many of these arrangements often relied on complex vacuum or hydraulic arrangements, restricting their viability.

Advances were made when, in 1955, engineer Robert Hays proposed a more straightforward, effective and electronically operated set-up. The proposed system could monitor the vehicle's current speed, thanks to conductive elements in its speedometer, and - when the car came to a rest - an electric motor would be engaged that would actuate the vehicle's rear drums.

This set-up would become the basis of virtually all future EPB designs, with all either electrically acting on existing parking brake components or making use of motor-on-caliper configurations to clamp pads to discs.

In the late 1980s, simple driver-actuated EPBs were reputedly used in industrial applications, with electronically triggered valves locking pressure in the brake lines - like a line-lock - and holding the vehicle still. Mazda was experimenting with an improved EPB in the early 1980s, too, which was automatic and featured a gradient sensor to improve its effectiveness. The patent for this particular configuration would go on to be referenced by countless other manufacturers in the following decades - including Volkswagen and BMW.

Unsurprisingly, it was the launch of a new flagship model that heralded the introduction of EPBs to the mainstream automotive market. The E65-generation 7 Series, revealed in September 2001 and introduced on 1 November 2001, was packed with equipment - including a Siemens-built cable-actuating EPB, active anti-roll bars and a direct-injection V12.

It was a close-run thing, though; TRW Automotive had been busy developing an EPB system, which featured a more advanced motor-on-caliper arrangement. It almost pipped the BMW to the market, too, finding its way into the flagship Lancia Thesis.

Unfortunately, despite being previewed in February 2001, complete details of the Thesis's hardware were not published until its full reveal on 6 November 2001. It was continually delayed, furthermore, and didn't reach the market until June 2002.

Regardless, the TRW set-up went on to be hugely successful - finding a home in myriad models, ranging from the Jeep Renegade through to the BMW i8. Now, more than 100 million are claimed to be in service. Their remit continues to be extended, too; recent developments include integration with cross-path reversing safety systems, preventing an accident if someone walks behind a reversing vehicle.

While it's hard to beat the instant on/off identification, and quick, easy action of a mechanical parking brake, ever-increasing safety requirements, automation and the demands of most customers means that EPBs will continue to rise in number.

[McGraw]

Had to have a new bumper on my car recently.

For some reason Audi A3s only engage the full parking brake automatically after the key has been removed when hill hold assist is engaged.

The light also goes out pretty quickly. We'd been sat in the car chatting for a while then got out...car wasn't moving.

I had temporarily turned off hill hold assist then turned it back on (or so I thought - the button doesn't always work). Parked the car and left it outside. Went back out to it and went in the boot..closing the boot caused it to roll off as the handbrake wasn't on after all.

Looked out of the window and it was in the middle of the road having bounced off next door's brick gatepost.

Pretty annoying as I could have sworn I'd checked that the handbrake came on when the key was out. I may not have been pushing hard enough.

[leakymanifold]

I had an original mini in my youth. Handbrake turns were epic fun in that thing....not sure it would have felt any bigger either having an electric handbrake instead of a lever.

[CaptainRAVE]

The problem comes when you move from a car where the parking brake is entirely automated to a manual parking brake again.

Moving my wifes car in the snow and wondering why it wasn't moving much. It was only the next day when I went to drive it that I remembered the lack of automated parking brake...oops!

[cptsideways]

If only all the manufacturers shared the same set ups, some are automated, some are not, some auto release some do not, some only when belted up. Some come on with the key out other do not. It can vary within one manufacturers range too. Some buttons are up, some down, some by your knee most in the centre console.

For what was a standard simple an idiot proof they have made things rather complicated. However as a rule applying the handbrake & holding it on whilst moving does do a nice emergency stop using all the all brakes still stationary.

[HardMiles]

Good article, but I keep seeing the same sentence in all of them; “being used in myriad models” for example.

Either my understanding of the English language is wrong, but that should read; “being used in a myriad of models”, am I correct?

Please help as it’s now bothering me!

[grahamep]

Not for me. As I understand it with electronic parking brakes you need an hookup to the on-board computer if you want to change your own rear pads. Don't mind putting my car into the garage for occasional repairs but I like to think I have a choice.

[Onehp]

Good explanation, but surely the very keen drivers on PH prefer a manual parking/hand brake?

The one on my GT86 of old was great, as strong as the disk brakes and perfect for initiating nice slides before the turn... Most others on most cars are too weak for any sliding fun beyond very slippery conditions, mostly snow or gravel... Still, don't want to miss out completely...

[Gad-Westy]

Really hated these things for a long time but that mainly based on experience with hire cars where I didn't necessarily spend the time required to learn how they're actually meant to work.

Now that I have a car with this, I really like the auto functionality. Only thing that troubles me is that the auto mode can be a pain in stop start traffic so I sometimes disengage it only to forget I've done so sometime later and a have a short panic moment. Think that one can be filed away under user error.

[Ares]

I'm a huge fan of electronic parking brakes. Can't see the downside.

I've only ever used parking brakes when parking, and having it has an on/off switch that automatically engages when the car is placed into 'park', with no chance of it not engaging fully, is a huge plus, as is the lack of a sodding great lever in the cabin. Neither are as easy/relevant in a manual though.

For my wife they are even better - her MINI is often parked on a slope, and not always having the strength the fully engage the parking brake, she has to leave the car in gear. Having an electronic brake totally negates that issue.

[PoopahScoopah]

cptsideways said:

If only all the manufacturers shared the same set ups, some are automated, some are not, some auto release some do not, some only when belted up. Some come on with the key out other do not. It can vary within one manufacturers range too. Some buttons are up, some down, some by your knee most in the centre console.

For what was a standard simple an idiot proof they have made things rather complicated. However as a rule applying the handbrake & holding it on whilst moving does do a nice emergency stop using all the all brakes still stationary.

Yup. When I was working away and getting a different hire car every week, I got caught out when they gave me a Toyota (Avensis I think it was) and I couldn't find the bastid button at first. Took a good few minutes to locate it down under the dash in the footwell. Jumping between different hire cars is annoying enough when you have to spend the first few minutes getting familiar with the different controls etc, so putting the handbrake button in different places is just plain bloody stupid.

[Krikkit]

cptsideways said:

If only all the manufacturers shared the same set ups...

Agreed - it should have been legislated early-on to ensure consistent operation, now it's a complete minefield.

[anonymous-user]

grahamep said:

Not for me. As I understand it with electronic parking brakes you need an hookup to the on-board computer if you want to change your own rear pads. Don't mind putting my car into the garage for occasional repairs but I like to think I have a choice.

Not for me, either. Seems like the classic 'solution to a problem that doesn't exist'.

[culpz]

My previous A4 had an electronic handbrake. I think i preferred it tbh. Do they generally work better in manual gearboxes or automatics? Or is the application pretty much the same for both?

Unless you're the kind of person who likes doing cheeky handbrake turns everywhere, i'm not sure why you'd miss it. The only point would be the reliability side of things, which i'm not sure of.

[Prinny]

As the owner of a v12 7-series as featured, it’s only fair to conment that while it works as an EPB, and as per Ares above, comes on with ignition off, therefore failsafe, it’s still one of the few epb cars that got it right in having an auto-release upon take-up of drive.

By contrast, the z4 (for example of a newer car) epb is useless as you have to have your foot firmly on the brake pedal to allow release of the epb. Then, you don’t use it, and just sit on the brakes instead.

More and more cars have the release functionality, but I wouldn’t buy an epb-equipped car without it now.

I still would prefer a manual lever though.

[beko1987]

My old Laguna2 had an EPB. Through the french 'fear' I NEVER used it bar when the car applied it when I turned it off. Then the cables streched slightly and I had a heck of a time getting it to pass the MOT, because I couldn't just adjust the cable.

[Gad-Westy]

culpz said:

My previous A4 had an electronic handbrake. I think i preferred it tbh. Do they generally work better in manual gearboxes or automatics? Or is the application pretty much the same for both?

Currently I have a dsg Leon and Mrs has a manual Leon. Both have the same parking brake arrangement. It works the same on each but you might argue it's better on the manual as you don't have to engage the parking brake to prevent creep in traffic. In the auto, you really need to turn the auto parking brake off to make smooth progress.

[Ares]

Gad-Westy said:

culpz said:

My previous A4 had an electronic handbrake. I think i preferred it tbh. Do they generally work better in manual gearboxes or automatics? Or is the application pretty much the same for both?

Currently I have a dsg Leon and Mrs has a manual Leon. Both have the same parking brake arrangement. It works the same on each but you might argue it's better on the manual as you don't have to engage the parking brake to prevent creep in traffic. In the auto, you really need to turn the auto parking brake off to make smooth progress.

I never use the parking brake except when parking? Foot brake prevents creep in traffic?
Did/do the same when in a manual.

The only downside I have ever come across is the slightly less convenience when in a strange manual with a EPB on a steep hill - more difficult to use it to get the bite point.

[RumbleOfThunder]

I thought that Grand Espace might've been first but that looks to be around 2002 onwards.

[anonymous-user]

Technology for technology's sake!

[Harris_I]

culpz said:

Unless you're the kind of person who likes doing cheeky handbrake turns everywhere, i'm not sure why you'd miss it.

Because I use the "Balboni method" of reverse parking (leaning out of the driver's door looking at the curb alongside and posts behind, especially in cars with poor visibility). EPBs usually slam on the brakes the moment the driver's door is opened. Not a fan.