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ibooster braking system logic issue [and discussion around brake failure claim in shanghai]

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I'm an old forum member that recently returned (was more active in the Roadster and Model S days) and also have not heard of braking system complaints.

There have been sudden acceleration complaints, which as linked by the NHTSA report have been investigated and found to be driver error.

This whole braking controversy seems to be something that had blown up in China in recently.
That maybe because Tesla is under the spot light in China now. Almost every accident Tesla involved would make national headlines.
 
I read about that incident before even the whole Shanghai protest. The lady that complained presented no evidence that the braking system failed and refuses a independent third party investigation into her car. She insists on a full refund plus other compensation.

However, the police report said the cause of the accident was improper following distance:
"Zhang’s father was the driver at the time of the car accident. According to the traffic police collision report issued that night, Ms. Zhang’s father failed to keep a safe distance from the other vehicles and was deemed to be fully at fault for the accident."
Tesla Responds to Braking System Failure Controversy in China Amid Social Media Frenzy - Pandaily

I also saw that video (the full one). The car was able to stop in the first try in the video (note they may have tried many times before, which they did not record). The second try in the video the guy listened to the lady and lifted his foot off the brakes two times to "pump the brakes" before applying full braking force and that was when they hit the wall.
Found a link to a Chinese site that should be visible in China too:
特斯拉再度回应"海南碰撞事故":刹车系统合格

From the videos I watched related to it, others have not reproduced the same problem. It seems however lifting your foot off the brakes would increase the stopping distance even if the system was functioning normally, and that can make a huge difference in the conditions they tested (wet gravel road at a short distance).

None of the videos I saw testing the Model 3 braking afterwards show the actual measured stopping distance between the two different methods. That should answer more of the question. I did do another search right now and this video does compare the different stopping distances.

The article linked to a video that you may not be able to watch if you are in China, but you can perhaps find the same video under a different video service with the title: 老司机试车:特斯拉真的刹不住吗?
See MIC Tesla Model 3 Braking Tests In China

50-0 km/h dry roads:
  • 14:56 - 7.39 m
  • 14:56 - 7.25 m
  • 14:57 - 7.31 m
  • 14:57 - 6.78 m
    Best: 6.78 m
    Worst: 7.39 m
50-0 km/h wet sandy roads (like in the original video):
  • 14:20 - 14.93 m
  • 14:22 - 15.34 m
  • 14:29 - 17.35 m
  • 14:30 - 18.22 m
50-0 km/h wet sandy roads with incorrect braking ("pumping the brakes", they say "点刹" in the subtitles):
  • 14:54 - 25.06 m
  • 14:22 - 24.11 m
  • 14:29 - 28.01 m
  • 14:30 - 22.3 m
That adds 4 to 13 m to the braking distance, which totally can mean the difference between stopping in time and crashing into the wall!


I just got a 2021 Model 3 SR+ right at the last day of 2020 and have not personally experienced any braking problems. Newer Tesla's no longer even allow you to adjust the regen braking (it is always full power), so I have set the car to "hold mode" so that it comes to a stop by itself if I let off the accelerator pedal. So I rarely have to use the brake pedal myself in most driving. However, when I do, the braking power is plenty
After watching the full video, I would agree with you that the other accident is probably due to pumping braking method, which is not the right choice under such road condition.
The EDR (maybe, not sure. haven't seen one before :p) of the young lady's accident is out (see below). It seems that her father drives too fast...
WechatIMG331.jpeg
 
Hi M3 owners,

Just placed an order for 21 M3 SR+ a few days ago. Not sure if any of you is aware of recent drama in Shanghai's autoshow. One of the Chinese M3 owners (probably 2020 model) claimed to encounter brake system failure during driving, which caused an accident. The investigation is still ongoing. After some research online, even in this forum, some owner had a similar incidence (Total braking system failure!!!).
There are some guys claim it is an software bug issue with the Bosch ibooster system on Tesla's car. Basically, Tesla writes its own code to synchronize the regen braking system with pedal braking system, putting regen braking's priority over pedal braking. Under some specific road condition (slippery ground, etc.), it will lower its braking assistance power, think regen braking is enough. Without braking assistance, the pedal will be hard to press down, feel likes it is not working. And it also will extend the stopping distance. If this is true, that would be a serious safety concern. There is another accident in China, the owner also claimed having problem with stopping the car on the wet ground. Ironically, the technician from SC reproduced the accident at the same site, with his own M3.

So my question to you guys/gals, is that have you ever encounter similar situation? having a hard to time to press the braking pedal and stopping the car on wet/slippery surface?

I really like the handling/accelaration of the M3, but my wife thinks I would give it up, for the safety concern. Even it is a rare case, when it happens, it is 100%.


Thank you in advance.

A possible future M3 owner
I only have 4014 miles on my 2020 M3LR, but so far I haven't experienced anything like this.
 
"Pumping" the brakes is never the right answer though many were taught that as it was probably easier to explain than threshold braking which is the preferred method.


I have never yet, happily, experienced any issue with the braking but I can say both the Roadster and my original RWD Model 3 had ABS-like behaviors activated during regen if the road surface was slippery. You'd feel the regen relax a moment to prevent the wheels from breaking traction much as ABS might.

Far off observation might suggest driver error and sensational media coverage following..

I should add that the purpose of modern ABS etc is to automate threshold braking - racers and others with pre-ABS cars might be experts but most folks not so much
 
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"Pumping" the brakes is never the right answer though many were taught that as it was probably easier to explain than threshold braking which is the preferred method.


I have never yet, happily, experienced any issue with the braking but I can say both the Roadster and my original RWD Model 3 had ABS-like behaviors activated during regen if the road surface was slippery. You'd feel the regen relax a moment to prevent the wheels from breaking traction much as ABS might.

Far off observation might suggest driver error and sensational media coverage following..
The recent update of the story agrees with you.
 
Hi M3 owners,

Just placed an order for 21 M3 SR+ a few days ago. Not sure if any of you is aware of recent drama in Shanghai's autoshow. One of the Chinese M3 owners (probably 2020 model) claimed to encounter brake system failure during driving, which caused an accident. The investigation is still ongoing. After some research online, even in this forum, some owner had a similar incidence (Total braking system failure!!!).
There are some guys claim it is an software bug issue with the Bosch ibooster system on Tesla's car. Basically, Tesla writes its own code to synchronize the regen braking system with pedal braking system, putting regen braking's priority over pedal braking. Under some specific road condition (slippery ground, etc.), it will lower its braking assistance power, think regen braking is enough. Without braking assistance, the pedal will be hard to press down, feel likes it is not working. And it also will extend the stopping distance. If this is true, that would be a serious safety concern. There is another accident in China, the owner also claimed having problem with stopping the car on the wet ground. Ironically, the technician from SC reproduced the accident at the same site, with his own M3.

So my question to you guys/gals, is that have you ever encounter similar situation? having a hard to time to press the braking pedal and stopping the car on wet/slippery surface?

I really like the handling/accelaration of the M3, but my wife thinks I would give it up, for the safety concern. Even it is a rare case, when it happens, it is 100%.


Thank you in advance.

A possible future M3 owner
If you're worried, just don't get one.

"synchronize the regen braking system with pedal braking system, putting regen braking's priority over pedal braking. Under some specific road condition (slippery ground, etc.), it will lower its braking assistance power, think regen braking is enough. Without braking assistance, the pedal will be hard to press down, feel likes it is not working. And it also will extend the stopping distance."

This is NOT how Tesla braking system works. People need to stop spreading this around.
The braking system in a Tesla is NOT a blended system. The physical brakes and regen braking are separated so what you described DOESN'T happen.
 
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As above, there is some real BS being spread around about the braking system.
On a poor surface the ABS will be operating all the time while braking and this makes the pedal feel dead because effectively the brake booster is taking over all the work. That is not the same as the brake booster delivering less assistance or failing. Those comments stem from a basic lack of understanding about how ABS systems work.

I do sort of understand why some drivers in emergency situations think the brakes have failed. It's usually because they haven't practised emergency braking before so the feeling of ABS and how the pedal feel changes with increased effort and the iBooster taking over is new to them. Because it's different, therefore it must be broken.
The only answer to that is more driver training/education, but that's not seen as a priority. They just want cars that are easier to drive and require less knowledge.

Pumping the pedal of course will increase braking distance not decrease it.
Turning off the ABS and using threshold braking can decrease the braking distance if you have enough skill. Most drivers won't have enough skill. That's why ABS was invented.

I've read about a couple of actual iBooster failures on Teslas, but that's nothing do do with what's being discussed in this thread. This incident in China came about from basic ignorance and trying to deflect blame for a crash. That does seem to happen quite a lot and it's sad.
 
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If you're worried, just don't get one.

"synchronize the regen braking system with pedal braking system, putting regen braking's priority over pedal braking. Under some specific road condition (slippery ground, etc.), it will lower its braking assistance power, think regen braking is enough. Without braking assistance, the pedal will be hard to press down, feel likes it is not working. And it also will extend the stopping distance."

This is NOT how Tesla braking system works. People need to stop spreading this around.
The braking system in a Tesla is NOT a blended system. The physical brakes and regen braking are separated so what you described DOESN'T happen.
That's what I heard before. I don't know if it is ture. That's why I am asking the question here. To spread misinformation is definitely not my intent. As for the blending, a few posts up, some one explained that for the AWD there is no blending, for the RWD, maybe there is some communication between regen braking and friction braking. I've placed the order before hearing the news. Otherwise, I would think twice.
 
There doesn't need to be any difference in the way the RWD Model 3 works in regard to braking just because regen is only on the real wheels. On the AWD cars the front induction motor only accounts for about 25% of the retardation in any case. The braking system can just do it's own thing and not worry about what the regen is doing.
 
In a modern Tesla the driver commands max regen with the accelerator pedal so there's nothing left to be blended with the brake pedal. Perhaps older versions set to "Low Regen" mode will never increase regen strength no matter how hard the brake pedal is pressed? I don't know. I do know that the RWD roadster would sometimes reduce regen under hard braking and it wouldn't surprise me if this logic carried thru to modern cars for improved ice handling.

But for a failure mode analysis we must consider the fact that the brakes and regen are fully intertwined and yes, blended. Cruise control seamlessly transitions from regen to regen+brake. One-pedal stop and go seamlessly transitions from full regen with no brakes to full brakes with no regen. You can even see/feel the brake pedal moving on its own.

That said, none of this is a "regen" issue, it's an (alleged) issue somewhere within the highly integrated stability, throttle, and braking system.

And that said, anyone who pumps brakes has no credibility on any automotive topic. Anyone who greases an ice skating rink and then drives a perfectly fine car over a curb for YouTube fame has no credibility on any automotive topic. And anyone who dances on a tradeshow car because her husband says he thinks he hit the brakes has no credibility on any automotive topic.

In other words, of course it's possible that this complex system could malfunction. But there is *zero* evidence that it ever has.

iBooster.png
 
it's weird that my last comment disappered. Got deleted?

Well, i also want to make sure whether Tesla has braking issues or not. I translated a car reviewer's test video ( in Chinese ) and posted an article below.


According to the team's test, in certain cases the regen and brake booster got somehow blended ( ISSUE 2 ). I'm not a pro and cannot judge, so anyone with any idea could leave a comment.
 
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it's weird that my last comment disappered. Got deleted?

Well, i also want to make sure whether Tesla has braking issues or not. I translated a car reviewer's test video ( in Chinese ) and posted an article below.


According to the team's test, in certain cases the regen and brake booster got somehow blended ( ISSUE 2 ). I'm not a pro and cannot judge, so anyone with any idea could leave a comment.

My comment is more along the lines of the fact that, when someone joins a website and their first interactions are to push a video and start talking about a specific issue like this, I instantly have a lot of skepticism.
 
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it's weird that my last comment disappered. Got deleted?

Well, i also want to make sure whether Tesla has braking issues or not. I translated a car reviewer's test video ( in Chinese ) and posted an article below.


According to the team's test, in certain cases the regen and brake booster got somehow blended ( ISSUE 2 ). I'm not a pro and cannot judge, so anyone with any idea could leave a comment.
As the OP, I suggest you to review all the posts above and make your own judgement.
 
it's weird that my last comment disappered. Got deleted?

Well, i also want to make sure whether Tesla has braking issues or not. I translated a car reviewer's test video ( in Chinese ) and posted an article below.


According to the team's test, in certain cases the regen and brake booster got somehow blended ( ISSUE 2 ). I'm not a pro and cannot judge, so anyone with any idea could leave a comment.
'Issue 2' is a description of how ABS feels on a Model 3 by someone without much experience of using it.
 
My comment is more along the lines of the fact that, when someone joins a website and their first interactions are to push a video and start talking about a specific issue like this, I instantly have a lot of skepticism.
Skepticism about what?
I do not know how the public respond to recent accidents in USA, but obviously the situation is not good in China. After series of accidents related to braking system and sudden unintended acceleration, lots of potential M3 buyers like me are now wondering whether M3 is really safe or not.
Since we are not pros and consider most comments in China now to be very emotional, we also want to hear voice worldwide. Is that intention strange?
I'm looking forward to more technical analysis instead of something else.
 
If regen were suddenly disabled when one wheel triggered ABS this would require the driver to press a little bit harder on the brake pedal to compensate for the lost regen braking on the 3 non-ABS wheels. This could be enough to daze the most feeble minded of drivers, such as the man in stopcrazy's video.
That's not how it works at all. The simple fact is the data from the original incident shows the driver didn't initially brake hard enough. When he did and ABS engaged, it was too late anyway. These tests done afterwards are just trying to find a way to blame the car when it was the driver's fault all along. Some people always want to try and find someone to blame other than themselves.