Brakes failed

[SCB86]

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.

I found this out in the snow - zero ABS activation when slowing down with regen led to the wheels locking and the car skidding. I only ever use regen 1 now in snow/icy conditions.

 

[Tim Green]

Do you mean the regen was strong enough to cause the wheels to lock up in snow?

 

[Gomev]

Do you mean the regen was strong enough to cause the wheels to lock up in snow?

It does suggest in the owners manual (P166) to use less regen in icy conditions.

Energy Regeneration Level Suggestions:

Driving Mode / Energy Regeneration

Eco / Heavy
Normal / Moderate
Sport / Heavy

It is recommended to choose Light or Moderate levels on
surfaces that have low adhesion levels (e.g. icy roads).

 

[Kithmo]

Do you mean the regen was strong enough to cause the wheels to lock up in snow?

Depends how fast you're going I suppose.

 

[AussiePete]

Hope this link works

@RichRead I’d really like to know more about this - it’s obviously very worrying. I’ve had this happen with an ICE when my foot went to the floor and almost ran into another car.

A couple of observations from the video and previous responses:

1. If your foot went to the floor you would hear a thud on the video as your foot hit the floor. There doesn’t seem to be a thud recorded on the video.

2. Unless your battery is 100%, KERS operates to slow the car down going down hill and when the brakes are applied and the accelerator is not. KERS does not operate if the accelerator is being pressed.

3. The car definitely accelerates when turning into the drive (you can even hear the motors powering up). This would indicate KERS was not operating and power was being sent to the motors. So it’s not just a brake failure - it’s a brake failure with power being sent to the motors which is 2 separate faults.

4. If it’s not driver error, then there would have to be a major issue as breaking and acceleration operate on different circuits/mechanicals

5. If you have non-genuine car mats I would check them to see if they have interfered with the pedals. I have seen this with the mats getting tangled in the steering rack which is exposed in the drivers footwell

 

[AussiePete]

Hope this link works

As an aside I am really surprised the air bag did not go off . I would have thought that this level of impact would have triggered the airbag

 

[SCB86]

Do you mean the regen was strong enough to cause the wheels to lock up in snow?

Yep. Slowing down from about 25MPH in the snow using only regen and the wheels locked from the force of the regen.
Only happened in level 3 regen though. Now I drive it in level 1 in the snow.

 

[SCB86]

As an aside I am really surprised the air bag did not go off . I would have thought that this level of impact would have triggered the airbag

It's surprising just how much of a smash modern cars can take before they feel the need to deploy the air bags for the safety of the occupants.

 

[Kithmo]

It's surprising just how much of a smash modern cars can take before they feel the need to deploy the air bags for the safety of the occupants.

Yep, lots of salvage repairable cars for sale listed as, "airbags not deployed".

 

[Tim Green]

The other way to look at that is the surprising amount of damage done to a vehicle at fairly low speeds. Obviously the crumple zones play a part....

 

[Lovemyev]

It's surprising just how much of a smash modern cars can take before they feel the need to deploy the air bags for the safety of the occupants.

I have been fortunate enough, not to be in a car when the air bags have been deployed.
Because when they ARE deployed, they are really violent in their operation.

 

[Ron61]

View attachment 4871Anyone had their brakes fail?
I’ve had it twice where when pushing the brake pedal it cancels the KERS but doesn’t engage the brakes. 2nd time was on our downward sloped driveway and ended up smashing into the house.
MG customer service not taking this seriously. I was wondering if anyone else has had same or similar issues?

"Foot Brake For added safety, the hydraulic braking system operates through dual circuits. If one circuit should fail, the other will continue to function, but greater pedal pressure will be needed, brake pedal travel will increase, and longer stopping distances will be experienced. In the event of a brake failure where only one circuit is operational, the car should be brought to a halt as soon as traffic conditions safely allow. DO NOT continue driving - seek an MG Authorised Repairer."

Found this in the MG5 user manual. If the ZS operates in the same way you could of had a brake circuit failure. Hope it helps.

 

[macd2401]

I have been fortunate enough, not to be in a car when the air bags have been deployed.
Because when they ARE deployed, they are really violent in their operation.

My ex was in a crash where she T-boned another car when it emerged from a junction. Damage to both was substantial, and the air bags left a hell of a mess, but she survived unscathed...I've never been so disappointed in my life

 

[rjb70stoke]

"5. If you have non-genuine car mats I would check them to see if they have interfered with the pedals. I have seen this with the mats getting tangled in the steering rack which is exposed in the drivers footwell"

I've had this before in an ICE car. Happily doing 70(ish) on the M5 in cruise control, when I had to brake. What I didn't know was the car mat was blocking the brake pedal. As I couldn't slow down I was panicking like mad, every lane was slowing down and I was ploughing on. Had to literally stamp on the brakes to release the cruise. Very scary and actually my first thought when I saw this.

 

[Stormgrey]

I go with Scriv/Dr Dave. I would be very surprised if the braking system is computer controlled, which it would have to be to have total failure. If some hydraulic component failed, it would remain in that state so would be easy to see. Hydraulics are very reliable.

A Toyota Prius has an indirect brake by wire system, so pressing your foot on the brake is not mechanically linked to the brake calipers. Never had a problem except the known braking and car drives over a slippery manhole cover etc and the brakes momentarily do less braking while a wheel is on the manhole, the lack of traction upsets the system

 

[Deleted member 2439]

A Toyota Prius has an indirect brake by wire system, so pressing your foot on the brake is not mechanically linked to the brake calipers. Never had a problem except the known braking and car drives over a slippery manhole cover etc and the brakes momentarily do less braking while a wheel is on the manhole, the lack of traction upsets the system

That happens with any car, you can actually feel the ABS working for a split-second ….

 

[johnd973]

Seems to be quite a slope on the driveway, could it simply be a case of the your foot slipping off the brake pedal or catching the accelerator as you enter the driveway? Foot slipping of the pedal could give the impression that the brake went straight to the floor. Can see the car bounce as it enters the driveway so it would be perfectly understandable.

 

[speculatrix]

Several things occurred to me when I watched the video.
Firstly that there weren't any swear words when the crash occurred!

Secondly, I can hear the motor spool down as the car turns into the drive, didn't hear any frantic pedal stamping, and I feel that the car free-wheeled into the house, rolling and accelerating down the short steep slope.

I've always felt that the accelerator is a little over to the left in my car, but then my feet aren't comfortable when pointing straight ahead, they naturally "manspread". Maybe not just me, maybe it is the car at least a bit.

I usually don't charge to full, so I always expect good regen. Cold weather as well as full charge can reduce the regen to zero.

Anyway, brake failure is obviously very
worrying for us all. I hope your problem gets diagnosed and fixed. It must be a very rare condition, but maybe there will be a recall for safety checks. The clicking steering problem affected many people, and that's another basic design and manufacturing thing that should be impossible to get wrong, so it's not like SAIC can't get simple basic things wrong.

 

[Kithmo]

A Toyota Prius has an indirect brake by wire system, so pressing your foot on the brake is not mechanically linked to the brake calipers. Never had a problem except the known braking and car drives over a slippery manhole cover etc and the brakes momentarily do less braking while a wheel is on the manhole, the lack of traction upsets the system

The Prius does have direct link to the hydraulic brakes, the ABS pump supplying the power assistance instead of a servo. If the ABS pump fails it still has hydraulic brakes the same as any other UK type approved car, but with no power assistance, like having no servo on a standard ICE car.
AFAIK no fly-by-wire braking systems have been approved for road use in the UK yet.
The apparent loss of braking on a manhole cover etc. is only on regen, due to there being no ABS on regen and the differential in the final drive only regen braking the one wheel.

 

[PaulWaun]

I'm sorry, but I would not take this seriously if I was MG either. The braking system is seperate and not computer controlled. So as long as there is no air in the brakefuid (could happen after maintenance) or the brakefluid got overheated (breaking for a long term going downhill) or a leakedge the brakes should work.

The only thing that could happen to let the brakes go is a faulty wheel speed sensor used for ABS. That system is electric and would cause ABS to activate when it shouldn't. Partially disables braking. Since you did not mention that I doubt that would be the problem.


I have never treid breaking and pushing the gas pedal at the same time. The brake could disable the engine on an EV. On a ICE car that is not always possible so i do not know if MG implemented that.

I have to disagree, although there is probably a direct input between brake pedal and hydraulics but there logically must be computer input for two reasons. First. AEB is a computer function, secondly there is no inlet manifold on an EV to provide activate the brake servo, the vacuum is provided by a pump which will be turned on/off by the computer
I have had instances where I feel, when slowing down at a junction for example, there is a brief period where I don’t feel the car slowing as much as expected and I have to brake harder. I’ve assumed it’s down to slight difference in technique between ICE and EV - when u slow down in a manual ICE you dip the clutch at last second so as not to stall but have both engine braking and foot brake until that point. In an EV, as soon as you touch the foot brake the KERS is cancelled i assume so the de-acceleration is foot brake only
The other question is, is the same computer used for AEB etc as the infotainment? If so it’s a bit worrying cos the infotainment response to anything is bloody awful