OPD, car rolls backwards when stopping on downhill slopes (merged thread)

[NLMGSAN]

I'd be careful what you wish for. MG may tackle the problem simply by significantly reducing the regen level when in OPD mode.

It looks like that is exactly what has happened. They flattened the regen profile with the last part of the braking cut at 20%.
I will try to mimic this reverse drive effect next weekend.

 

[Howard68]

Definitely real. Happened to me twice today using OPD and coming to a halt at the base of a slope with light use of breaks and then releasing the break. Probably happened today because I was breaking more than usual because of wife in the car. The car felt like it went back a metre. Probably not that far in reality but several decimeters, not “a few centimetres”. So this has not been fixed in over a year? (In Australia in a late-2024 model Excite).

 

[Howard68]

@Rockstar this just happened to us on the weekend with our brand new MG HS + EV.
Within two days of ownership the vehicle shifted into reverse on three separate occasions while in Drive. Each time, the only way to correct the issue was to turn the car off and restart it. This issue was witnessed by my passenger and discussed in real time.

On Sunday night my husband was driving the car when it happened again. However this time the vehicle reversed suddenly with force, narrowly missing our child who was walking behind the car. The car then collided with our house

A brief search online indicates other owners of this car who have had similar incidents. So far, I have the names of 20 Australians who have commented on two MG Facebook pages, about this happening to them.

This is an extremely dangerous defect that could have resulted in serious injury or worse. Given the severity of the issue, I have requested the ACCC to investigate immediately.

Let me know if you had any response.
Thanks.

Were you using OPD?

 

[NLMGSAN]

Were you using OPD?

It looks like that is exactly what has happened. They flattened the regen profile with the last part of the braking cut at 20%.
I will try to mimic this reverse drive effect next weekend.

Forgot to report back. Steepest slope to test it is about 7% here. But only very short. I did need the breaks to get it stopped. Car did not reverse.
Regen did go all the way to 25 when breaking. So it looks like dropping OPD regen levels does not have an influence. Maybe it does if the slope is less steep and the car stops on OPD only?

 

[my291]

I believe happened to my S5 EV today too. Any feedback on this from the mg dealers? I'm in the UK

 

[tsedge]

I am a bit baffled why able-bodied people like OPD.

In my view EVs are nicer to drive without it (so long as they have Auto-hold). I have driven a OPD car but it felt weird and I did not feel I could always trust the braking. Seems much more natural to me to always come on to the brakes to bring the car to a stop and it feels safer.

I know some people love it to the point where they won't drive a car without it but it totally baffles me why. I'd genuinely like to understand it if anyone can shed some light?

Since OPD was retrofitted to the MG4 relatively recently then it isn't a surprise that the implementation is buggy and needs some work. Then of course not everyone will have the latest software updates so the bugs will persist (even on newly sold cars made a while ago) for a long time.

With these problems it sounds to me like the OPD software is calibrating itself on each start and so when starting on a hill which requires significant hold back to stay stationary, it over-corrects causing reversing when on a flatter surface, then re-calibrating to correct itself. Something like this is my best guess.

I would suggest maybe giving each new technology a wide berth for a few years until it "just works".

 

[DixieTGS]

I know some people love it to the point where they won't drive a car without it but it totally baffles me why. I'd genuinely like to understand it if anyone can shed some light?

I can't explain it rationally either, and I'm in the OPD camp. Mostly it just feels 'right' or the natural way to drive. All the differences seem very minor to me and are dealt with subconsciously whether in OPD, non OPD or in a manual ICE.

I think the biggest difference for me is actually the 25% regen, which in my mind should be available in non OPD mode too so actually not relevant to your question. I believe when I get SC077, this advantage will be reduced or dissappear entirely.

Driving in crawling or stop start traffic also seems a bit smoother, but the difference is tiny.

 

[Tuareg]

I've used OPD on some occasions, maybe once a week, never had any issues with it. Just a matter of getting used to the slightly different driving experience, felt very good and enjoyed learning something new.

 

[Roger001]

I am a bit baffled why able-bodied people like OPD.

I have to say that I have driven an MGB for the last 32 years, while I've only had my MG4 for about 7 weeks.

OPD seems the most natural way to drive a car, even after such a short time period. I want to move forward - push the pedal down, I want to slow down - lift the pedal, and I want to stop, take my foot off the pedal. I just wish the car would not reset the feature if I cycle around all the drive modes via a steering wheel button (it is turned off when you select snow mode, I believe).

There is a vast amount of complexity to provide such a feature, but it is a nice simplification of the driving process from the driver's point of view.

As for the issue at hand, MG are going to be found responsible for such an issue in most Western countries as and when an insurance claim (or worse) goes to court, but as with all car manufacturers, they will not act as if it is an issue until they have 'improved' their software and deployed it to as many cars as possible as part of the standard maintenance cycle.

 

[tsedge]

Ok, thanks folks.

So it sounds like people feel the experience is simpler and more natural with a single pedal and having adapted to it, why would one want to go back to two pedals?

I can understand that and I am sure I could adapt to it if I had to. I still feel there's a safety argument here - it depends on the car providing enough braking and there being time to move one's foot onto the other pedal and press it in an emergency.

But on the other hand I don't want to become a fossil who pretends that double-declutching is the pinnacle of driving, along with setting the timing and cleaning out the distributor. I have driven automatics for years prior to having an EV and the simplification argument is a similar one.

 

[Roger001]

In part, it may seem natural to me as the MGB does not freewheel when I take my foot off the accelerator between the engine, gearbox and overdrive, there is a lot of resistance breaking as standard, so the MG4 just does it far better.

Don't forget that the MG4 has the emergency braking covered anyway with its Autonomous Emergency Braking feature.

 

[tsedge]

In part, it may seem natural to me as the MGB does not freewheel when I take my foot off the accelerator between the engine, gearbox and overdrive, there is a lot of resistance breaking as standard, so the MG4 just does it far better.

Don't forget that the MG4 has the emergency braking covered anyway with its Autonomous Emergency Braking feature.

Ah well, mine is currently being turned off due to false positives - it was good for a long time previously though - so I guess that depends on your faith in it always working when it needs to.

 

[Roger001]

I've driven an MGB for 32 years. I have no faith in any feature of a car as just about every feature has failed at least once. I do find having too much braking force is far better than having no braking force

 

[MattyS]

OPD does appeal to me given that I only use my left foot to drive due to my disability, BUT I like having a bit more control over braking and see the 3rd level of regeneration on my 1st phase MG4, a bit like a more aggressive engine break scenario similar to an ice car which I prefer.

 

[siteguru]

My SE SR doesn't have OPD ... the car crawls at about 4 mph, so a bit like a torque converter automatic. I much prefer this mode of operation.

 

[decrep]

I still feel there's a safety argument here - it depends on the car providing enough braking and there being time to move one's foot onto the other pedal and press it in an emergency.

I feel that's exactly the same as driving without OPD, you still have to move your foot from accelerator to brake.
If you're used to OPD, you know it's not sufficient in an emergency and your foot will go straight to the brake pedal.
The difference here is that in between pedals you're getting full regen braking, where as if going slow the car will be rolling.
All the reflexes are still there, in my experience it's not a problem.
The foot goes from one pedal to the other in a flash.

 

[tsedge]

You make some good points.

It is the specific situation of gentle braking due to a hazard ahead that suddenly becomes an emergency, which worries me. With two pedal, my foot is already pressing the brake (regen notwithstanding) and I can instantly push harder as needed. With one pedal I have to raise my foot, move it across and then press down.

Then I also wonder about lack of familiarity if I am not often braking, will I react appropriately in an emergency?

These are, I'll admit, just worries. I will readily concede that the papers are not full of stories about OPD crashes.

 

[decrep]

Then I also wonder about lack of familiarity if I am not often braking, will I react appropriately in an emergency?

You'd have to be a very poor driver not too. If you've been driving for a while, it's muscle memory reflexes, that say go for the brake pedal, no matter how long you've been using OPD.

I suspect the time it takes for the brain to send a signal to the foot, is longer than it takes the foot to swap pedals.

It would be good to have some reaction times done, then you can make up your mind with some science behind it. But from my personal experience, I'm confident, in my case it's not going to make enough difference to worry about.
But I'm in the habit of leaving a lot of space between me and the car in front, admittedly, on the freeway, that space can disappear very quickly, when a jam up happens, but then my foot is on the brake pedal.

 

[tsedge]

You'd have to be a very poor driver not too. If you've been driving for a while, it's muscle memory reflexes, that say go for the brake pedal, no matter how long you've been using OPD.

But what about new drivers who only learn with OPD? I thought reflexes required regular training.

I suspect the time it takes for the brain to send a signal to the foot, is longer than it takes the foot to swap pedals.

Yes, reaction time could be the bigger component but the total will be longer with OPD.

But I'll stop now (no pun intended!), as I have no evidence to present.

 

[Ian Key]

You make some good points.

It is the specific situation of gentle braking due to a hazard ahead that suddenly becomes an emergency, which worries me. With two pedal, my foot is already pressing the brake (regen notwithstanding) and I can instantly push harder as needed. With one pedal I have to raise my foot, move it across and then press down.

Then I also wonder about lack of familiarity if I am not often braking, will I react appropriately in an emergency?

These are, I'll admit, just worries. I will readily concede that the papers are not full of stories about OPD crashes.

Interestingly China appears to be banning OPD in new cars from 2026 because of crashes where drivers claimed despite pressing the brake pedal the car wouldn't stop. Investigators found that they were actually pressing the accelerator.

https://www.autoevolution.com/news/china-to-ban-one-pedal-driving-mode-that-was-widely-blamed-for-tesla-sua-crashes-234766.html