Electromechanical Parking Brake operation

[Mike789]

I have a new 2013 spec A3 fitted with the electromechanical parking brake, i.e. there's an electrical switch to apply the parking brake and also to disinguage it.

I do not have the hill-assist system fitted. This is an optional extra.

 

So to apply the parking brake I pull up the switch and when I'm pulling away forwards it seems to disinguage itself with no further action from me.

I find however that if I'm pulling off in reverse it doesn't disinguage itself. I have found I can get it to disinguage by lifting my clutch a little and effectively rocking the car which seems to disinguage it.

 

You can force it to disinguage by pushing the switch however in order for this to happen you need to depress the footbrake.

So here's the problem: If you're trying to pull off in reverse up a hill, you need your foot on the footbrake in order to release the parking brake. So you can't be applying a few revs and using the clutch because your foot is on the brake pedal (unless you employ some fancy footwork).

 

This seems a bit of an error to me in the application of the parking brake system fitted to the car.

You can purchase the hill assist system but this is a cost option and obviously you needed to have had selected it on purchase. If its needed in order to be able to pull off on a hill then it should have been a standard fitment.

 

It was much easier with a manual handbrake, you could apply as much pressure as you wanted as and when you wanted it. With this new electrically controlled system, its either on or off.

 

Bit of a drop off on an otherwise great car!

[Tech]

Hi Mike, I am now on my second of the new shape A3's with the electromechanical parking brake. It should work in reverse too. One thing that is apparent with the new A3 is they have gone back to the operating logic of the old A6 parking brake where the EPB control unit must register enough torque from the engine and lifting of the clutch to disengage. Therefore, you need to sometimes apply more throttle than you might expect to have.

The also do have a short term hill hold assist feature as standard, which holds on the brakes on a hill for two seconds, just enough time to switch your right foot from the brake to the throttle without ever needing the parking brake. This works on the inclination of the hill you are on and the gear you are in so if you are facing uphill and have it in first gear, it will hold on briefly, but if you are in reverse it will release straight away. Likewise if you are facing downhill and have engaged reverse, the hold assist will hold for two seconds, but if you have first gear engaged, it will not. They do have the optional hill hold assist that you mention with the button for long term hold assist, but they all come with short term hold assist as standard.

Try it, the whole system works together quite well when you get used to it. You'll probably find you then only use the parking brake when you actually park up or feel your going to be sat in a traffic queue for some time.

Tech

[Mike789]

OK thanks for that Tech, sounds like I need to try a few things out with it.

I havent actually needed to pull off in reverse up a hill yet, but the reason I mentioned the reverse thing is that I definitely have had a couple of occasions where it failed to release and the car was raising itself up against the parking brake. On both occasions this was trying to reverse off my drive which is actually slightly downhill towards the road. It was only on the second occasion I spotted the warning on the dashboard telling me to depress the footbrake before I could manually take off the parking brake.

My wife fell foul of it too the first time she tried to use my car (much to my amusement) with me trying to jesticulate to go forwards first. She got there in the end but more by trial and error.

I will try a bit more throttle then and see if that does the trick, and if not I might even mention it to my dealer in case there's a slight fault with it.

It's not causing me an issue though and like I said before, its otherwise a great car.

[Bald Eagle]

I had a newish A3 as a courtesy car and needed to reverse uphill away from my inlaw's garage.  It seemed to release the handbrake a bit early, so the car rolled forward a few inches before i got to the biting point.  I kept chickening out and pushing the footbrake.  So I kept edging onto a steeper slope and nearer the brickwork!!!

 

In the end I just had to bite the bullet and give it a bit more wellie and lift the clutch a bit faster.  Phew - finally moving away from the building!!!

 

I think that one was in need of some adjustment as well.

[Tech]

Ah right I see what the problem is now Mike. For the auto release of the electromechanical parking brake to work you need to have the drivers seat belt fastened and the doors closed, obviously as a safety feature. You only need to depress the foot brake and manually release if you haven't got your belt on or if you have a door open. I'm guessing you leave your belt off to turn around and see better when reversing out of your driveway?

[Mike789]

Thanks Tech, but I always put my belt on straight away when I get into the car so this isn't a cause of the problems, and my door is closed.

I think its probably just being new to the car and am not giving enough revs. This is probably more so pulling off my drive as its actually slightly downhill to the road so I may be building less revs than I would be otherwise.

I'll keep an eye on it and see if its just simply down to my driving style and getting used to a new system over the new few weeks.

 

Coincidentally, I borrowed a new B-Class Merc a couple of times recently with a similar electro-mechanical brake, but this seems to operate differently. After you'd come to a stop with the foot brake, it then held until you pulled away. I don't know what the time limit was for pulling away and I don't know if it had a hill-assist system option fitted. This was good when you got used to it but what I really didn't like was that they'd put the manual parking brake switch in the dashboard hidden behind the steering wheel and on the right hand side. This was hard to find (although I realise you'd get used to it). At least the Audi one is in a position where you'd expect it to be.

[CHIPPO]

These parking brakes are useless , less than useless , god know's why they bother fitting them its a gimmick to over come a non exisitant problem. 

 

It removes all driver control from a very important function.

 

The one on my A4 is far to slow to respond leaving the brakes dragging during anything but a very tardy start

 

Great for Audi giving premature brake wear and potentially clutch wear, but most importantly a lack of car control if one lands up juggling clutch and brakes to  try and prevent roll back , this is poor driving technique and should be frowned upon, this most likely explains why we sit in traffic staring at brake lights permanently on , but then Audi can sell lot sof replacement lamps to !   Also promotes warped disc's as the with the caliper clamping the disc once stopped this will cause hot spots and warps . oh more spare parts and bills , god it's all win win for Audi. 

[Bald Eagle]

These parking brakes are useless , less than useless , god know's why they bother fitting them its a gimmick to over come a non exisitant problem. 

 

It removes all driver control from a very important function.

 

The one on my A4 is far to slow to respond leaving the brakes dragging during anything but a very tardy start

 

Great for Audi giving premature brake wear and potentially clutch wear, but most importantly a lack of car control if one lands up juggling clutch and brakes to  try and prevent roll back , this is poor driving technique and should be frowned upon, this most likely explains why we sit in traffic staring at brake lights permanently on , but then Audi can sell lot sof replacement lamps to !   Also promotes warped disc's as the with the caliper clamping the disc once stopped this will cause hot spots and warps . oh more spare parts and bills , god it's all win win for Audi. 

 

To be fair, any handbrake that operates on discs can cause hot spots and warps, this is not just limited to the newer electromechanical ones.  

 

I did once come across a guy who sold his Mondeo just because of all the things that MIGHT go wrong with it, rather than what ACTUALLY went wrong with it.  Please don't work yourself into a depression over discs that haven't warped yet just because they might!

[CHIPPO]

I wasent specifically concerned about the parking brake and hot spots its about poor driving when some one sits on the brakes at lights.

 

My S has rear discs and the handbrake works directly on these pads. They are made by Nissin and are useless, they will cease up on a regular basis especially if not used on a regular basis, mine lasted 68k mile before a seizure! The other problem with these is that if the discs are hot when the handbrake is applied as the discs cool and shrink you can find your can wandering down the road on its own. Happened once to me , neighbour knocked to adivse my car was across the end of the road. 

 

Not likey to be a problem with the Audi system as the brakes are rammed on so hard by the servo motors every time.

[Tech]

Hmm, I've been keeping up with this thread and a few good points have been made, but a few slightly mis-informed ones too.  So here is my input:  

 

It is worth remembering that Audi are not the only company fitting EPB, even Citroen have been fitting them since 2004 and I do believe one of the very first examples of a production car with EPB was in fact the Renault Modus, about the same time as the A8.

 

It is a very good point that feedback has been taken away from the driver to an extent, and there can be a delayed reaction in the auto release of the parking brake.  Hot spots on the discs are really not a concern, the car needs to be held by some sort of brake when stood so whether it is the footbrake, a mechanical parking brake or an EPB, the discs will still be clamped (unless the parking brake works on a drum design such as the Q7).  I have never known a set of brake discs warp due to hot spots, it is usually due to imperfect fitting during replacement or overheating due to poor driving.

 

The emergency brake specifically is far better on an EPB style system (if you haven't yet tried it, make sure your on a quiet road first!) It also really does de-clutter the centre console and saves having to make a strange shaped armrest to fit around the handbrake such as in the BMW 3 series.  

 

Of course on the downside, the parking brake is a pain to release if the car looses battery power or ignition functionality. 

 

One thing is for sure, EPB is here to stay and Audi are only one of many manufactures using the technology.

 

 

 

Here is a statement from Audi suggesting the benefits of the system, make of it what you will:

 

The electromechanical parking brake offers many advantages over the conventional handbrake.

Greater freedom in designing the interior
The handbrake lever has been replaced by a button. This allows greater freedom designing the interior layout, especially the centre console and footwell.

More functions available to the customer
The electronic control system and CAN network means the electromechanical parking brake includes additional functions for the customer, such as hill-hold assist.

Easier to manufacture
Since the handbrake lever and handbrake cables are no longer needed, production and assembly of the vehicle has been simplified.

Capable of self-diagnosis
The electromechanical parking brake is a mechatronic system, so the system functions are continually monitored. The handbrake cannot be applied or released electrically if the battery goes flat but the brake callipers can be mechanically released by a qualified technician.

[Audi Owners Club]

Sounds like this new parking brake require a bit of getting used to!

[CHIPPO]

YES they are hear to stay with Audi and every other manufacturer fitting them, and I know of Citroen drivers and LR drivers who hate them too. 

 

How do you incorrectly fit discs and cause wharping? If the rear of the new disc is clean and burr free and the hub surfce is clean and burr free the disc should bed down true to the hub. Not sure if this is the case with Audi discs I presume they are secured with a couple of small CSK screws to the hub for assembly, and fully secured by the wheel nuts/bolts. Now unless you check the disc for true with a DTI I cannot see how this can cause warping. Warping is invariably as a result of either poor disc manufacture and anomolies in the cast iron, the cast iron being green and ageing badly or localised heating and cooling. This most likely on the front discs that do all of the work depending on the apportioning valve setting. Then sitting at the lights riding the clutch, foot on brakes. The rears suffer less as they dont get as hot. My S uses the rears so sparingly that the big probem is rusting of the friction surface and pitting. I changed my rear disc's for pitting, not worth having them skimmed as they cost didly squit to replace new, they were well within spec thickness and could easily have been skimmed. But at £25 each not worth doing.

 

I think  the arugument form Audi regarding the ergomonics of the interior is a bit lame, the reason they are fitting them is more than likley cost engineering  over a conventional cable operated system. I suppose there are limp wrists who have trouble applying sufficent brake force to hold the car on the flat in a stiff wind. Thier other arguments are not exactly pertinent either. All adding to comlexity with no real user gains in the efficency of the system over the convetional ,  again it just removes driver control and feel.

 

Also I have realised I am already moving off from standstill compensating for the delay in brake release by effectively releasing the clutch in a two stage process slipping it slightly, this will cause preature wear , shame it will be some poor secound owner who picks up the tab for this as with all manufacurers Audi will surely not pay for a new clutch at 50k miles it will be driving style,, not a fault with the clutch.

 

I have never worn out a clutch yet , best to date was 190k miles in a Citroen C15 van that was totally abused being driven through its life fully loaded, it was also still on the riginal rear brake shoes and front discs , i think total of 4 sets of front pads. A recent Fiesta Van I drove for 65k miles was still on only 50%  used front pads. So it wil be interesting to see if the rear pads on my A4 last , I suspect they wont as they are dragging virtually every time I Pull away

 

I can get smoke from my front discs on the S if i try hard, around North Weald for instance and on the odd occasion after a spirited drive braking hard into corners repeatedly, with no problems, but then i do allow them to cool with the brakes released. The clutch is at 74k and is fine despite being worked very hard on occasion messing about trying to get quick 0-60 times. Never got any where near those quoted in EVO 

[Tech]

Well, you have kind of answered your own question with regards to incorrect fitting.  You would be surprised at how many people fit new brake discs to a car without cleaning surface deposits from the hub at all.  This has obvious implications.  The bedding - in procedure (something I consider part of the job of fitting new brakes) is also crucial.

 

Warping, from an engineering point of view, is in fact very rare on well manufactured brake discs.  We have been speaking of warping, I guess, as what people mostly perceive as disc warping.  

 

Most people consider the following symptoms to be a sign of warped brake discs:  

 

Juddering when braking

High run-out measured with a DTI

Discrepancies in disc thickness when measured around the disc with a micrometer

 

Of course, this could be a sign of warped brake discs, but 99% of the time is is not, it is just that people know no better because 'warped discs' is the commonly assumed cause, and they have no access to equipment or knowledge of methods to check otherwise.

 

What is mostly the case is an uneven deposit of brake pad material is left on the surface of the brake disc, causing the variations in thickness that are perceived as 'warped' discs.  This is of course colourless and not detectable visually.  The most common cause of this is that the brakes have overheated due to mis-use.  As the pads reach their temperature limit the transfer of pad material to the disc surface becomes uncontrolled and deposits unevenly.  As these deposits are then 'baked on' they remain to give that annoying brake judder which is diagnosed as 'warped discs'.  

 

Holding the brakes on once stopped can have consequences if it is following heavy braking (e.g. an emergency stop on the motorway followed by being sat in a traffic queue).  This is not due to hot spots on the disc, but rather imprinting pad material to the disc and having the same effect as above.  

 

The work load of the brakes between from and rear is much more evenly split nowadays.  As the brake compensating valve/proportioning valve has become obsolete and its function replaced by the ESP system the rear brakes can be given a much higher proportion of the workload than in the past.  The brakes are applied more or less evenly between axles until the point where there is a chance of the rear brakes coming close to locking, then the EBD (electronic brake force distribution) function of the ESP serves to maintain set fluid pressure to the rear brakes but allow the fronts to keeps increasing, thus rendering a compensation valve superfluous.

 

I personally have not noticed much difference between the mileage that cars with EPB get and ones with mechanical handbrake get and same with the clutch.  Of course, it is very much down to driving style and ability, more so than anything else.

 

Tech

[CHIPPO]

TECH , whats your position in Audi ?

 

I agree "bedding in" is important , agian there seems to be a wide range of opinions about howto go about it, I sort of use 50 mile sof normal driving and try to get few long soft brakig  sessios in from relatively high speed. I suppose this is also dependant on how much scoring is evident on the discs.

 

The last time I had discs changed as a result of juddering was about 25 years ago on a Ford Escot Company car , the juddering did disappear , but as you say there could be any number of causes. This was a brand new car with about 5 k miles 

 

I had a set of pads on the S that left deposits on a regular basis , Mintex , usually after soem hard braking ,it didnt cause juddering just noise , this would go after a few moderate applications of the brakes. These pads were changed at 5k miles as the friction material was literally breaking up , not very good . Went to Ferrodo DS2500 which were perfect. Currently have OEM Honda as the shims needed changing, also very good pads , some report they give up on track days.

 

Your comment s regarding ESP are interesting and not something I had not consdiered. Interesting lots of actions and reactions that all work to act on the braking system.

 

Driven my car for the last 2 day in and around town, and there is definate drag from the parkig brake when getting away sharpish, or when I manage to get away smoothly I am now slipping the clutch a tad more to allow the brakes time to disengage. So there will be additional wear over what my driving style would have previously imparted to both brakes and clutch.

 

Had numerous SS system failres today and yesterday

[Tech]

Chippo, I do not like to discuss my position too much on here as the manufacturer has a dim view on staff presence on forums, but I am one of the senior technical staff in the network.  I just keep a presence here to try and offer a bit of technical advice to people where I can.

 

The pads you have in your Honda currently, are obviously the one chosen by the manufacturer for the best combination of usability and efficiency for the type of driving they expect the average S2000 driver to be doing.  There is always a compromise to be made with any vehicle component, with brakes it is the compromise between high efficiency when hot and good co-efficient of friction when cold.  

 

Racing pads tend to be really good at staying efficient and stopping the car well once they are warmed up (when mated to the right discs of course) - however, they tend to be not so good when cold, and quite noisy/squeal too.

 

The pads fitted to small city cars tend to be much more quiet and have a good co-efficiency of friction when cold (less pressure required on the brake pedal), but would fade quickly under racing conditions.  

 

There is always a layer of pad material left on the disc after bedding in, this helps give a good co-efficiency of friction, but it is when this layer is unevenly distributed due to the wrong type of brakes being fitted for the driving conditions that juddering can occur.

 

What exactly were the start/stop failures you have felt?  Have you demonstrated them to a Technician at your local Audi Centre?

[CHIPPO]

I agree with you regarding pad choice, the Ferrodo pad can be a bit lifeless when cold , but excellent when hot.  The HOnda OEM pads are I presume made by Nissin as they supply the braking system, but of course that may not be the case as a fair bit of development was done on race tracks including Susuka and Nurburgring. They are a good balance, and many have no problems on track days with them. They are certianly ok for me as I do not do track days or am particulary hard on brakes. The Mintex pads I used once just seemed to fall to peices after relativly few miles of normal use. I have managed to get the OEM pads to smoke on a few occasions but still with no appreciable fade.

 

The biggest problem with the OEM Nissin brakes is the rear calipers seizing up, usually as a result of rust on the pistons and or the handbrake mechanism, The slider pins can seize too. Most of the problems can be prevented with good maintenence. The brakes themselves are efficient and only need to be upgraded for serious racing, and even then only the fronts.

 

The stop start issues i have fall into 3 distinct areas , with to my mind no particular set of circumtnaces building up to failures. I am told the investigation is ongoing with no previous problems reported to Audi. It has happend within a couple of miles from a cold start and earlier when fuly hot, but I would think these time scales are more to do with the parameters that the SS system monitors before it is allowed to work rather than any preliminary to the subsequent failures. They seem in general to be totally random. It has been suggested that it was my driving style, but i drive another car on a regular basis from another manufacturer that has SS with no issues, the dealer tech has also driven with me and has stated that i do not drive unusually in any way. 

 

The three stages are as follows:-

 

1) Engine fails to attempt to start when clutch is depressed no attempt at all, retry and it will start. I would estimate this happens maybe 1 in 15 stop start cycles 

 

2) Engine fails to start when clutch depressed, but does turn over, with tacho reading approx 700rpm but the engine fails to start 

2nd atempt or 3rd engine fires up, This happens approx 1 in 20 SS sycles

 

3) As in 2, but the engine will not restart on subsequent attemts, and the stop start failure message appears on the display behind steering wheel advising that a manual start be carried out, the engine starts. When the engine trys to start and turns over to my ears it does not sound like an engine turning over and failing to fire, its sounds very rough with quite serious vibration almost like it is attempting to run on one pot! 

 

There have been no faults recorded by the cotrol system. I was surpirsed the engine start fails are not recorded as Events, albeit not as faults.

[Tech]

Very perculiar, I have never come across such problems with the start stop system before. It is quite a mature technology now and has been around on the A4 since 2009 so all the common issues have been ironed out. The first point does indeed sound like a stop start system issue but points 2 and 3 sound like engine fueling/management issues seeing as the start stop is doing its job and attempting to start the engine. Did any of the faults occur when you was out in the car with the Technician? It may be difficult for them to find due to the sporadic nature of the fault if they have not experienced it first hand. It's Sod's law that the perceived fault doesn't occur when it goes into to workshop.

[CHIPPO]

Tech 

 

That was my thought that maybe it was an engine problem rather directly to do with the SS system. My fault reallly I reported this idea via a recptionist in the first instance and forogt to suggest it to the technician. Will send an e-mail later, stictly on the QT of course. As you say the SS system is attempting to start the engine and its the engine that fails to start.

 

Yes sods law did come to pass it wouldnt do it once when out on a test drive ( did it 4 or 5 times this evening on way home during the first 4 miles prior to M-way. But yes it is always very tricky to sort problems that are intermitant I know only to well from my own industry. 

[CHIPPO]

Still no answer Audi cannot find a problem !

 

So its onwards and upwards with the complaint 

 

Not much happens in this forum , does it , its like a morgue 

[Mwangamutlema]

I visited the in-law's and reversed into their steep drive. I stopped about 10 inches away from their new composite door. Applied handbrake and stuck it in 1st gear. I slowly let off the foot brake and it held.  The next day, I jumped in the car and found I had a problem. I wanted a controlled start from the steep hill and could not just pull straight out on to the main road without first pulling forward a bit to see. I thought  about releasing the handbrake and holding the car on the footbrake while feathering the throttle with the heel of my right foot while releasing the clutch and then slowly the brake. What if I stall it it or shag up the take off. Front door carnage I feared. I decided to let Audi take control and brought the revs up. It did not want to release. I gave it some more and it still was not happy. I then gave it the beans, slipped the clutch and it eventually released with a strange jolt that required fancy control of the clutch and throttle to keep things in order. I then had to stop to check the way was clear and did it all again. It was easier when I thought I was not going to end up in the Porch! I like proportionate control not binary. I now have something that is a lot newer but a lot worse, not a fan I'm afraid!