Emergency use of EPB

[IanL]

I have read the description of the Electronic Parking Brake in the Service Manual, and it seems to say that it uses part of the ABS System to control its application, to ensure smooth and progressive braking when the car is moving. Seems like a good idea. It also says that it will do the same thing, but not using the ABS (maybe not as well?) if the ABS has a self-detected fault.

I have given it a try at low speed (about 20 mph), and it just seemed to lock the brakes solid - nothing smooth and progressive. I'm wondering if anyone else has tried, and what their experience was.
I expect if I just take it to the dealer and say it doesn't work as described, I'll just get the usual BS - nothing wrong with it reply, so It would be nice to know how anyone else's works first.

Link to the Service Manual https://www.ksoulev.com/electric_parking_brake_epb_description_and_operation-2420.html

 

[notfred]

I tried it when I first got the car at about 50kph / 3 in the dry. I only applied it for a second or so (i.e. not to full stop) and while it didn't actually lock the wheels, it did brake aggressively - make sure that there is nobody behind you! That was before the recent EPB firmware update, so things may have changed.

 

[JeroenE]

I don't think it explains what VDC means, or at least I don't understand what they're referring to.

I think you're talking about the Slow Ramp Up (SRU), am I right? It does say this only works when the VDC has failed. So if that isn't the case I don't see why this would activate.

My point being that the VDC might be working as designed and that the design of the VDC doesn't include a slow ramp up.

That being said, I have activated the parking brake by accident while driving and it sure wasn't gradual and smooth. It released itself, probably when I pressed on the pedal again. This was quite some time ago, though. Probably in 2015 or else 2016.

Another thing that my car didn't like was pressing the pedal while the brake wasn't fully engaged yet. Case in point: I was stopped at a traffic light, I was waiting and put on the parking brake. Just as I did that the traffic light turned green and I pressed the pedal. This result in a lot of beeping and no movement. I'm not sure what I was supposed to do. Turning the car of and on again helped to rectify th situation. Of course by that time the light was red again.

 

[IanL]

Thanks for the replies. Its true that the manual does not define VDC, but I understand it to be Vehicle Dynamics Control, which is a collective term for ABS, TCS and ESC, which is described as being carried out by the IBAU.

You may well be correct that if it has not determined that it has failed, the described slow ramp up will not manifest itself. I have found that emergency (panic!) braking with the pedal seems to bang the brakes on hard and promote locking-up, rather than the rapid intermittent braking that ABS should provide, so I'm wondering whether my IBAU has an undiagnosed fault. Notfred, have you experienced the same thing?

 

[notfred]

I definitely have working ABS, it will pulse the brakes during hard breaking.

 

[IanL]

Thanks, I don't believe I do. I'll have to have a go with the dealer.

 

[JejuSoul]

I just tested this on my 2015.

Driving on a dry, quiet, straight, road at 50km/h. I pulled the EPB lever up.
The car braked suddenly. At the same time there were warning beeps from the dash.
I don't think there was any 'pulsing' of the brakes. Just hard deceleration.
The dash showed strong regeneration occurred. I didn't have torque running at the time.

This test was the first time I have ever done this.
Warning. Never push the stick from D (drive) to P (park) while the car is driving at any speed faster than a crawl.

 

[IanL]

Thanks for that. My assumption that EPB application would invoke ABS is obviously wrong,

 

[notfred]

Did the EPB literally lock the brakes solid and cause the wheels to skid?

I'm also concerned that your brakes lock up and skid when you panic brake with the foot brake. I think there is something wrong in your ABS system. With wet roads and bumps that can cause a wheel to hop, and definitely in the winter with the snow and ice, I have full ABS and it is a noticeable feel in the pedal and noise.

I tend to drive in B and that also avoids locking a wheel (through the same ABS wheel sensors), however it's quite dangerous in that it takes a significant fraction of a second after releasing the regenerative braking before applying it again. It almost feels like the car has started accelerating. You need to be quick on the brake pedal and use the proper ABS to avoid it crashing in to whatever you were braking to avoid. In slippery conditions it is often safer to drive in D rather than B.

 

[IanL]

Thanks, Notfred. I think it did cause the wheels to skid. I agree that there is something wrong with my ABS, but the mechanic at my local KIA dealer, who tested them, says he could find nothing wrong. He said he would file a report, so that KIA could get a picture if there was a pattern of complaints, but I've heard no more.

Our Government has a vehicle testing station for inspection of imported and doubtful vehicles. I think I will ask if they can test ABS systems. If I get a written report of the problem from them, maybe KIA will change the ABS unit (the IBAU).

I take your point about driving in B mode (which I always use), but I gathered that the system is supposed to blend the regen and friction braking, which it usually seems to do quite well. Perhaps not so well when ABS is active. I'll try it in D mode.

 

[IanL]

Well, I tried in D mode, and there was a difference (faster response, I think), but it was still not behaving properly. I decided to give it the best opportunity I could, by ditching the original Michelin tyres on the back, despite them still having plenty of tread, and fitting Goodyear 4Seasons G3 to match those on the front. (I'd previously ditched the only slightly worn unknown brand fitted on the front as potentially the cause of my problem, and the steering certainly improved, but I was still unhappy with the braking).

The result - the ABS and the emergency use of the EPB now works as described by JejuSoul and Notfred. I can't understand why this should be the case, but there must be some sensitivity in the software which is upset by particular tyre characteristics. Anyway, I'm happy now, and learned a lesson, don't mix the tyre brands/types on a SoulEV :!:

As a bonus, the car feels much improved as regards roadholding - money well spent

 

[notfred]

I wonder if the tyres were slightly different diameters from different tread depths and patterns, and that was enough to upset the ABS and cause it to not function properly? It means regular tyre rotation is very important.

 

[IanL]

Good point.