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Brake assist is scary af

27K views 116 replies 42 participants last post by  Madokami 
#1 ·
I managed to trigger it again today.

50 to 60 mph. Traffic slowed, then stopped. I put just too much brake in too fast and.... holly crap, full brake abs engaged!

I lifted off the brakes, reapplied and got the hard peddle, lifted again and all worked fine again. We all lived.

I get why it’s a feature, but I feel bad for the guy in the 90s lumina behind me. I bet he went home fuming about some jerk in a blue car that brake checked him.
 
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#42 ·
I will say the times it's happened to me on the street, I wasn't laying in to the brakes & only applied maybe moderate pressure. I really think it only has to do with reaction time from gas to brake.
 
#43 ·
I'm going to agree with everyone saying it's all in how quickly you move from the skinny pedal to the brake, since I only experience this when I rev match without heel and toe. I generally take my time modulating the brake to keep from being rear ended, so when I rev up, downshift, then switch to the brake, I get the panic brake going off and the tailgaters behind me freak out.
 
#44 ·
Haven't had it happen yet, but with the sheer amount of WHOA this car can generate I can see why it would be super sketchy.

This thing stops so fast I constantly check my rear-view mirror. It's super important to leave space for the normal cars behind you to stop because they can't do what we do.
 
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#48 ·
All,

Yes I've experienced this on the track... Its not good at all! I think if I had an instructor in the car at the time they would tell me to park it.
I've had it happen about 5-6 times but I can't pin point what triggered it as it happens on different brake zones around the track But mostly from longer straights braking from over 100 mph. At WGI into turn 1, into the bus stop on the back straight and into turns 6 (the laces) and T7 (the toe).

I did experience this with stock rotors, calipers with race/track only pads and high temp fluid. (Pads were G-Loc, Carbotech, Motul 600, Motul 660) It doesn't matter. I don't recall if it happened with the RB big brake 380 mm cast iron rotors and 6 piston calipers. At that time I was playing around a lot with different pads.

But now that I've upgraded my brakes to what's shown in my signature I haven't had it happen. Of course with this set up I can leave a little extra cushion of braking maybe 3%. So I maybe (subconsciously) not applying as rapidly or just off threshold.

I would love to have a re-calibration for the brakes for this and ice mode. Please automotive manufactures allow for track mode to turn this off!!!!!

I'll be back at WGI in Sept so I will be looking for it.
 
#49 ·
Just happened again on the street (QEW in Ontario Canada) and I hated it, and feared it, more than ever. Ford enginers (or is it Bosch or someone else?) have decided I ought not brake just "some" early in anticipation of the issue which was likely but far from guaranteed. No need of full stopping power given the traffic behind me. FU%K!
 
#50 ·
I just spent about 30 minutes on quiet roads to test this out. It definitely has to do with how quickly you move from the accelerator to the brake, but also how rapdily you press the brake pedal. You do have to press the brake with a certain amount of force, you can't just do a quick transition with light braking. That said, you do not have to get onto the brakes with "abs-triggering" force. What also seems to happen is that the ABS modulators are instantly active even though there is no WAY that the braking force applied to the brake pedal is even close to triggering ABS. So, it might FEEL like full braking ABS, but it isn't. In my unofficial tests, from 30mph doing the quick gas-to-brake transition with just enough force to get the "crunchy braking" and I let it stop the car it would be a certain distance...maybe 30 feet? If I instead hit the brakes hard and engaged the real ABS, it'd stop in half the distance. So, it seems to be that the quick transition is triggering some sort of instant brake modulation even without a wheel locking up.

It also seems to take a little while to re-charge. If I trigger the brake-assist, I can't trigger it again for about 15 seconds or so.

I guess I'm smoother on the track as I've never experienced this until this thread brought it up.
 
#54 ·
This is not true. to use the drift stick you need to be in drift mode and then disable all aids. All the new ABS flash does is disable the ABS when you pull the drift stick. If you get on the brakes too hard ABS will kick in, and if you are pulling the drift stick and you get on the brakes the drift stick will stop locking up the rear wheels and ABS will kick in.
 
#57 ·
I've had to push pretty hard on occasion and my worry has always been the car behind me - kind of defeats the purpose of good brakes. Never triggered the assistance and I have no doubt if it brought you to a rapid stop you might look like a complete doofus. It would also trigger the flashing brake lights I would imagine, but I also suspect that these would be activated on sudden application of the brakes, without necessarily activating the assistance. Currently at 40k kms and hope it doesn't happen in the wrong circumstances. Thanks for bringing it to our attention......
 
#58 ·
Alright, I payed very little attention to this until this morning when I experienced it, and boy is it scary...

I've had the car since early 2017 and have never had this happen on the street or on the track until today. My guess is that I usually try to keep a lot of space between myself and the car ahead of me on the freeway or the street, so I never have had the need to "panic brake" at speed. Could be due to my history or riding motorcycles and having a habit of "looking ahead" to predict what's going to happen in front of me. I have had to panic brake a handful of times, but I was going quite slowly (backing out of driveway, parking lot speeds, etc), so the affects might not be very evident.

This morning, I was cruising along the freeway going 70 mph. I briefly look down to my SYNC screen running Android Auto to change the podcast I was listening to, and was abruptly greeted by a trucks brake lights in front of me when I looked back up. I quickly stomped on the brakes as a reflex and the car nosed down so quickly I had to consciously pull my foot away from the brake pedal to regain control. I also caught a glimpse of the headlights of the Dodge truck following me get very uncomfortably close to my rear on the rear view mirror.

At the track, I don't usually brake quickly either. I try to brake late, but from all the driving training I've done, I've been taught to keep all my inputs applied gradually to make transitions as smooth as possible as not to shock the system. I'm still not that great with late braking, but when I do, I do brake hard but push down gradually, so I'm guessing the brakes aren't applied quick enough to be interpreted by the car to be a panic brake situation.

Even though it did what it was supposed to do, I think its still a safety risk for some who expect the car to behave a certain way.

Was there a new calibration available to fix this issue? I vaguely recall reading something about it either here or on FB but have not found anything come up on my Ford Owners site.
 
#60 ·
Was there a new calibration available to fix this issue? I vaguely recall reading something about it either here or on FB but have not found anything come up on my Ford Owners site.
You may be thinking about Bulletin 7411:

11/27/2018 7411 -2016-2018 Focus RS - Momentary soft or Long brake pedal in cold/wet/damp weather - reprogram anti-brake system (ABS) Module

2016-2018 Focus RS vehicles with 2.3L EcoBoost engine, may experience momentary soft or long brake pedal in cold/wet/damp weather after extended driving conditions. Reprogram the ABS module using the latest software level of appropriate Ford diagnostic scan tool. For claiming use causal part 2C219 and applicable labor operations in Section 02 of the service labor time standards (SLTS) manual.

but I don't think this had any effect on brake assist.
 
#67 ·
The first time brake assist mode kicked in for me, it scared the s**t out of me too, so next time at the track, I decided to play with it. In my 2018, it seems that it engages in normal and sport modes, but I wasn't able to get it to trigger in track or drift mode. Perhaps it's smart enough to disable it for track driving, since you REALLY don't want that at the limit of traction going into a turn.
 
#69 ·
Haven't tracked mine since 2017, but I definitely induced the panic assist at Watkins Glen in track mode. Mostly just annoying, although a late pass at 120+ heading into the Bus Stop scared the sh1t out of me when the assist kicked in. yeesh!
 
#72 ·
Following this.. I hate the brake assist. Plenty of times has scared the crap out of me coming in hot to a turn and the car thinks I'm trying to avoid an accident. I find it more dangerous than useful.
 
#75 ·
I’m sure it is different if you are competing for time (autocross or time attack etc) but for a normal HPDE I can avoid brake assist by taking a half second to ease on the brakes rather than stomping them. I’ve had instructors tell me this is good practice anyway.

I know the feeling of brake assist because it happens frequently in snow, but I have 9 track days in the RS and I’ve never triggered it on track. If I ease into the brakes I can quickly progress to threshold braking (sometimes locking up for a split second and backing off) without the brake assist triggering.
 
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#79 ·
Thanks for your reply and I take your point that it is possible to drive around this feature. (Bug).
Also it seems like statistics back it up as a safety improvement for a lot of road driving situations. We SHOULD have the option to switch it off for motorsport.
The direct connection between my foot and the pressure at the calipers helps me pitch, turn, unsettle, point as well as slow the car, I'm continually (both consciously and unconsciously) judging surface grip, tyre wear and suspension set up through the way the car reacts 'under brakes', and having some other force intervene in the name of 'assistance' is un-nerving, un- necessary and counter productive.
I'll keep adapting and eventing the car while chasing a work around technically. Any further thoughts or ideas are welcomed.
 
#77 ·
I'm just learning to coast before hard braking at autox. It definitely costs me time if it kicks in during an autox run.

Absolutely no one from Continental will return my calls or emails. I know it's a liability thing, but I'd love to speak to a Continental engineer for 5 mins just to see how it works, not necessarily how to bypass it. I haven't looked into the possibility of the AccessPort datalogging brake pressure. I'm not sure if there's a parameter for that in the ABS module. I don't think anybody has cracked the body module that supposedly houses modes and ABS stuff. It would be awesome to start the car in Sport Mode with ESC disabled.
 
#81 ·
There must be a way to either hack the RDU, or create a standalone unit. I am literally at the end of my patience with this car's incessant attempts to think and act for me. It was annoying in summer, but now in winter it's ridiculous. I want ABS and stability control off.

Permanently.

I drove it for a while with the 40 amp ABS fuse pulled, and the brakes were much improved, totally predictable and locked as I desired. But of course the rear drive would only operate at about %10 torque.

I honestly wish I had gone with my initial inclination - buy a normal Focus and put an Evo drivetrain in it.
 
#84 ·
I want ABS and stability control off.

Permanently.
You can achieve this while retaining the RDU functions in one of two ways. Essentially, until someone figures out how to program the ABS control unit the only options are to separate the electronic and hydraulic functions of the system.

Option #1: Plumb new brake lines directly from the master cylinder to the brakes, with a manual proportioning valve. This is what Team O'neil and Hoonigan did. You will lose the torque vectoring and eLSD functions implemented through the brakes. You can install a mechanical LSD in the front to help mitigate the loss of eLSD (on a 16/17) but torque vectoring requires the ABS unit.

Option #2: Install a second complete ABS unit which is not plumbed hydraulically but only connected to the car's ABS harness. This will have the same negatives as above, and in addition the brake bias will be less than optimal.

Unfortunately, neither of these approaches leave you with a vehicle with the dynamic benefits that it brings to the table in the first place. With the RDU lacking it's supporting systems the car becomes much less controllable and unpredictable and at least in a rallycross setting it is slower. Notice that neither of the groups that did this are still running the RS...
 
#82 ·
@HiluxSR5 I disagree about losing stability control. Yes when I want to slide around and have fun I will fully disable tcs/esc. But the focus RS’s ESC is very very very good. Having that option to run it is a massive plus.

I was sliding around on snow covered forest roads and it kept kicking in with the weird brake assist. I’m not that smart so I don’t think I could help at all. But there must be a way to fix this while also retaining abs.

What computer controls the ABS? Does it have its own module? Can it be swapped with a foST or foSE and try to figure out if this is foRS specific?
 
#83 ·
It is an RS-specific Continental ABS control unit, which also controls the RDU.

Part of what you are experiencing is Ice Mode, which can be exaggerated by Brake Assist kicking in first. In your case with the smaller calipers and different pads you are way out of the spec that the system was tuned for, which is likely having a negative effect on all of the ABS related functions, including the electronic brake bias system - which then can trigger the other two.
 
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