Brakes failed

[Jto]

My brake stopped working a few months ago. It was my foot accidentally touching the accelerator that did it.............:-(

I do not like the sound of this, did the pedal go all the way to the floor at the reported here.

 

[Lovemyev]

I have found it possible to hit the brake and the “GO” pedal at the same time, by having your foot at a strange angle.
Not just on the MG - It was also possible on my previous VW PHEV.
The ZS EV has a creep facility as we are all aware, so the car will be propelled forward with no action from the “GO” pedal at all.
The brakes are needed to prevent any movement.
The car will travel at around 3 MPH on a flat surface without any pressure applied to the “GO” pedal at all.
My point is, even with the very slightest amount of light pressure applied, the car is at 10 MPH and above very quickly.
So just by catching the “GO” for a brief second, can catch you out.
Even edging forward in a car parking space that has a wall etc in front, can be a little difficult to control.
You are unable to disable the creep control, so in tight situations you find yourself holding back the car on the foot brake.
As soon as you release the foot brake, the car wants to rush up that 3 MPH instantly.
Fine when you are creeping in traffic, but when trying to nudge slightly forward, it can catch you out.
I am a little surprised that none of the airbags where deployed as hitting that solid object with no deflection you would of expected a reaction ?.
Maybe the slower speed saved the day.
Swinging in off the road and then dropping down quickly, straight onto a heavy sloop driveway, I don’t think the collision avoidance system had a chance to read and react fast enough.
The drive way is fairly short and drops very quickly after leaving the public road, you do not get any second chances to react if your foot is not 100% correctly positioned on the foot brake that’s for sure !.
Good luck with your investigation and subsequent repair.
At least you where not injured .

 

[weedavemac]

Having just watched the video, my first thought was 'ouch!'

I have no suggestions as to what caused the collision.

All I can say is glad you are okay and hope you get it fully resolved.

 

[Sark21]

My sympathy. I sometimes very wary of shooting forward into house as my drive on a steep slope too only longer.Until I get outside charger fitted I have to turn into the house wall and close up so power lead will reach through window.

I wouldn't trust auto pilot to drive in if you where using it at the time.It states in handbook on bends and dips it may not detect objects in time.Speeds above 27 mph may not always avoid collision.

I've had to jump on brake a few times when approaching traffic at stand still in auto pilot.I wasn't going to give it the chance not to stop.

I haven't tried it yet but I think handbook says you can pull emergency brake switch up to apply handbrake.I realise you wouldn't have the time to fiddle about to locate switch.

 

[Sark21]

 

[Sark21]

 

[Kithmo]

The video shows there was no slowing (or speeding up) at all when it got down to 4mph, as if there was no braking at all.
Do you drive with one foot, changing from accelerator to brake to slow down, or two, one on each pedal, left foot braking ?
The reason I ask is that it's possible to be pressing the foot rest instead of the brake pedal if you use both feet, which would give exactly the scenario I see in the video.
If you use the right foot for both pedals then there is a problem.

 

[Tim Green]

You would certainly expect it to be "fail-safe". However, I have no idea of the design and it is strange to me to have automatic items working on the braking system at all!

 

[Kithmo]

What surprises me is that the power is still applied to the motor when both pedals are pressed, I can see the motor overriding the brake if the brake pedal is only lightly pressed, very worrying.
I'm pretty sure that on my Prius the application of the brake, even lightly, would cut power to the motor and the ICE.

 

[Tim Green]

That could be another carry-over from the ICE version, as I haven't heard of any ice autos that cut power when you apply brakes.
If the owner thinks it was not his error, the car needs a really thorough investigation.
Remember all those cars (cannot remember the make) that were automatic and the drivers said they were "surging" for no reason -turned out to be true, I think.

 

[Lovemyev]

What surprises me is that the power is still applied to the motor when both pedals are pressed, I can see the motor overriding the brake if the brake pedal is only lightly pressed, very worrying.
I'm pretty sure that on my Prius the application of the brake, even lightly, would cut power to the motor and the ICE.

I thought I would try something today.
While parked on a empty car park, I put the car into drive and tested if it was possible to press the footbrake and the “GO” pedal at the same time with my right foot and see what happened, this is what I found.
When you have your foot in a position that is over to the right of the foot pedal and not dead central, what happens is this.
While the foot brake is taking up the free play / travel, the outside of your right footwear hits the “GO” pedal before the brake pressure is sufficient enough to hold back the car.
At this point the motor is stronger than the light pressure applied to the foot brake.
So, as you push harder the car continues to move forward.
Extra pressure and increased travel, then makes the foot brake more powerful and pulls up the car harshly.
So, with your foot incorrectly positioned and NOT applying foot pressure correctly in the centre to the foot brake, it is possible to effectively bridge the both pedals with one foot.
If you shoe size is large, then I think the chances are increased.
If the free travel point of the footbrake, was less or the “GO” pedal decreased, then this could not happen, because the foot brake would have firmly engaged before the “GO” pedal was touched.
I hope this makes some sense ????.
Just to say, if pressure is applied to the centre of the foot brake pedal, then this situation does NOT happen.

 

[JodyS21]

What surprises me is that the power is still applied to the motor when both pedals are pressed, I can see the motor overriding the brake if the brake pedal is only lightly pressed, very worrying.
I'm pretty sure that on my Prius the application of the brake, even lightly, would cut power to the motor and the ICE.

I'm shocked that it does not cut the power to the motor as soon as the brake pedal is even slightly pressed, that's such an obvious thing to put into the programming.

 

[SCB86]

I have on a couple of occasions "brake boosted" my ZS off the line (timing the 0-60 sprint on a country road) I can confirm that the cars brain doesn't cut any power to the motor if the foot brake is also engaged. With both pedals pushed to the floor the car strains against the brakes and the moment you let go of the brake the car launches cleanly away.

 

[Lovemyev]

Heath and safety has dictated for a long time now that the braking power of a car, must exceed the propulsion power that can be created by the car.
So, should there be a problem and the Go pedal / throttle pedal etc become stuck for some strange reason, then the brakes have to be stronger enough, to reduce the speed of the car, or it just becomes like a run away train.
This holding back of the force generated by the power unit of the car, by holding it stationary with more powerful brakes, is effectively how launch control is achieved.
Build and hold the power, hold it back with the brakes, then release the brakes !.
Fun, but not that good for your car or wallet when repeated on a regular basis.

 

[macd2401]

I dunno.... Sadly these days there's no manual brake handle to pull that you can use to stop the car!

If you pull the parking brake switch up, the brakes will come on (as long as there isn't a fault that would stop it working). It basically throws everything on, it sounds hellish, but it does work.

 

[Deleted member 2439]

Heath and safety has dictated for a long time now that the braking power of a car, must exceed the propulsion power that can be created by the car.
So, should there be a problem and the Go pedal / throttle pedal etc become stuck for some strange reason, then the brakes have to be stronger enough, to reduce the speed of the car, or it just becomes like a run away train.
This holding back of the force generated by the power unit of the car, by holding it stationary with more powerful brakes, is effectively how launch control is achieved.
Build and hold the power, hold it back with the brakes, then release the brakes !.
Fun, but not that good for your car or wallet when repeated on a regular basis.

This logic only applies when stationary …..

 

[RichardC]

I experienced the following scenario last night.

I was coming up to a roundabout and had my foot hovering above the accelerator and letting KERS do the braking. The road surface at the junction had recently been planed as it is due to be resurfaced. As I moved from the tarmac down to the planed surface the car jolted over the bump in the road. My foot must have made contact with the accelerator as the car picked up speed. Luckily I was able to manually brake but it was a bit of a shock.

I know that this probably is not what happened with the OP but I thought it was worth mentioning.

 

[Lucky5]

I was coming up to a roundabout and had my foot hovering above the accelerator and letting KERS do the braking. The road surface at the junction had recently been planed as it is due to be resurfaced. As I moved from the tarmac down to the planed surface the car jolted over the bump in the road. My foot must have made contact with the accelerator as the car picked up speed. Luckily I was able to manually brake but it was a bit of a shock.

This was probably regen braking being removed rather than acceleration as you went over the bump. If the car detects bumps regen is reduced presumably for stability as the wheels have lower grip at that moment. Our Leaf does this too.

 

[Kithmo]

I experienced the following scenario last night.

I was coming up to a roundabout and had my foot hovering above the accelerator and letting KERS do the braking. The road surface at the junction had recently been planed as it is due to be resurfaced. As I moved from the tarmac down to the planed surface the car jolted over the bump in the road. My foot must have made contact with the accelerator as the car picked up speed. Luckily I was able to manually brake but it was a bit of a shock.

I know that this probably is not what happened with the OP but I thought it was worth mentioning.

Could also be the regen letting go as the wheel that was braking slid due to the differential being in the drive train, there's no ABS on regen. I used to get this with the Priuses.

 

[RichardC]

Thanks guys for your responses. Useful information and much appreciated.