Model 3 braking failure reproduced with video

[skywalker2go]

Hi M3 owners,

I live in China and have planned to buy a M3 since last year. But recently the Tesla Protest Event in Shanghai autoshow got wide attention in China's social media. For detailed info plz refer to AUTOSHOW Chinese woman’s Tesla protest prompts 5-day detention, company apology. (Short Version: Ms. Zhang claimed to encounter braking failure during driving, which caused an accident. She had previously negotiated with Tesla many times without any progress, and Telsa only promised to resell her car in accident to some else, without apology and refund. And Ms. Zhang refused to do so and played the drama in public.)
Since both sides still have not released any effective and professional evidence, the public have to wait and watch. Tesla DID provide some data to both public and Ms. Zhang. But according to some public digging, Tesla did not include the most important braking Pedal opening and closing related data, and the info given is too less to make solid proof. Ms. Zhang also declaimed to doubt that, but was unable to provide any effective evidence, either.
Ok, that's the long background. (Hope you guys still have patience ). In the past few days, some pros and car reviewers have commented on this event, one of them uploaded a video on a Chinese popular platform

特斯拉Model3刹车变硬，双车耐久测试工程师报告公开​

Since it's spoken in Chinese, i would do some simple translation. The Tittle means Brake of Tesla Model 3 becomes stiff, Double Autos' Endurance Test released. The reviewer has done lots of tests and comparisons betweent two kinds of autos. This video is a special one focusing on M3.
At the beginning he says that he personally feels sorry for what Ms. Zhang suffered but does not support the method that she took in autoshow. Then he asks: whether their team has encountered similar braking system issues during test? The answer is YES.

• ISSUE 1 （ 01 : 10）：Brake's Heat-fade Performance, much obvious than the others，detailed info will be released in another video；
• ISSUE 2 （ 01 : 25），declaimed ABNORMAL：in certain situations regen function gets limited，brake pedal becomes stiff and stopping distance gets longer. He mentions, for experienced drivers they may be aware that the brake pedal could still work with very very large strength， but for newbies， they will find the brake pedal hard or “impossible” the use. But why the are regen and brake booster blended， they could currently not figure out.
• ISSUE 3 （ 02 : 40），declaimed WEIRD：in vehicle vibration situation，regen function gets totally disabled and stopping distance is obviously much longer. According to Chinese regulations GB 21670-2008 this case should not happen（03：05），which clearly defined braking system should not be affected in vehicle vibration situation. And he also complements this test is based on their own procedure，which may not be exactly the same as national standard procedure.

Fianally, the reviewer also addresses that braking system comes certainty without a doubt the top priority. When such potential issues occur，the auto manufacturer should not ignore them or find any excuse, but try their best to confirm and solve issues ASAP.

I was confident in Tesla's quality in the past, but after watching this video i got really lost and one of the video's comment mentions:
The real dangerous part of a stiff brake pedal is not how hard it is to press, but the time lag that you take to first realize it’s stiff and then press with very large strength. This several hundred milliseconds are long enough to take your life in some extreme situations.

 

[Dangerous Fish]

Issue 1 - brakes overheating and fading after several high speed stops is totally normal, especially with the non P brakes. It's the same with any heavy car fitted with 'regular' non performance brakes.
Issue 2 - brake pedal becomes stiff etc. This is describing the normal operation of ABS. The tester is obviously not familiar with how ABS works. Yes braking distance is longer with ABS than threshold braking without ABS. Same with any car fitted with ABS.
Issue 3 - I can't tell from the video what is being described with this. Maybe you can translate more of the video and text on screen?

The quality of the video and the tests themselves are sub-optimal. No measuring equipment in the cars (such as a VBOX), no detailed methodology that I can see, all subjective opinion of what the tester thinks he feels.

Sorry, but this all appears to me to be normal operation and nothing 'abnormal' or 'weird'.

 

[skywalker2go]

Issue 1 - brakes overheating and fading after several high speed stops is totally normal, especially with the non P brakes. It's the same with any heavy car fitted with 'regular' non performance brakes.
Issue 2 - brake pedal becomes stiff etc. This is describing the normal operation of ABS. The tester is obviously not familiar with how ABS works. Yes braking distance is longer with ABS than threshold braking without ABS. Same with any car fitted with ABS.
Issue 3 - I can't tell from the video what is being described with this. Maybe you can translate more of the video and text on screen?

The quality of the video and the tests themselves are sub-optimal. No measuring equipment in the cars (such as a VBOX), no detailed methodology that I can see, all subjective opinion of what the tester thinks he feels.

Sorry, but this all appears to me to be normal operation and nothing 'abnormal' or 'weird'.

Thanks for the comments. I will forward your opinions under that video.
Sorry that i missed some info

• for issues 2, the tester has already addressed that it's ok with experienced drivers, but not for newbies. And they could have accidents in such situations;
• the reviewer has declaimed that this video is a special version ( for quick response to the event ), later detailed comparisons and data will be released.

 

[Dangerous Fish]

Thanks for the comments. I will forward your opinions under that video.
Sorry that i missed some info

• for issues 2, the tester has already addressed that it's ok with experienced drivers, but not for newbies. And they could have accidents in such situations;
• the reviewer has declaimed that this video is a special version ( for quick response to the event ), later detailed comparisons and data will be released.

ABS is designed for newbies! It's so they can continue to steer the car away from danger even when stamping on the brakes. Without it the wheels would lock up and the car would carry on straight regardless of how the steering wheel is turned.
This all comes down a lack of driver education and training. It's nothing to do with the vehicle itself.

 

[skywalker2go]

ABS is designed for newbies! It's so they can continue to steer the car away from danger even when stamping on the brakes. Without it the wheels would lock up and the car would carry on straight regardless of how the steering wheel is turned.
This all comes down a lack of driver education and training. It's nothing to do with the vehicle itself.

I know what ABS is designed for and what to expect when ABS is triggered. But what i want say (which i also think the reveiwer wants to address), in such cases, ABS-like behavior is NOT expected. If someone drives fast on slippy ground, a sudden brake will probably trigger ABS. But if the road condition is good and he is not driving very fast (or even slow), will ABS be expected? Definitely not. But that is what quite a lot drivers declaimed after accidents: stiff braking pedal (ABS-like behavior), the reason behind has been tallked a lot in Chinesed forums.

Here I would post some of these technical analysis, leave a comment if you think something is wrong. For those who can read Chinese, plz refer to the link 基于数据分析特斯拉事故原因. Since it's a long post, i would just put some conclusions.

In Ms. Zhang's case, given the data release by TESLA, after some simple calculation. The author has drawn a picture and he made comparisons among 3 parameters：cylinder pressure, ABS and the real acceleration. And he finds that cylinder pressure nearly matches ABS, however both differ a lot from real accelerations values.

In the first 2.5s before braking, cylinder pressure almost matches real accelerations values, after 2.5s, cylinder pressure increases rapidly, but the real accelerations values got limited, and within the key 1.8s after ABS' triggering, both the driver and ibooster have provided far more braking pressure than what the car's acceleration actually needed, but Tesla's ABS just output a small acceleration (~0.55g), which cannot even reach the standard threshold ( 0.9~1.1g ), this leads the final accident. Besides, there is no evidence that shows the road condition is bad. Since Tesla rewrites lots of software and logic of ibooster and low-level algorithm in ESC and high-level control algorithm. This part, especially how ABS control, Electromagnetic valve control, ESC, ibooster and regen get blended, probably should be responsible for this accident.

At this point, there is no need to confirm whether the calculation is right or not ( in fact a lot of analysis got almost similar results ), just focus on the above conclusions based on the calculation.
I'm not auto pro, but I'm an engineer, from above analysis i could personally not find obvious logic issues. So are the conclusions right?

 

[Dangerous Fish]

I know what ABS is designed for and what to expect when ABS is triggered. But what i want say (which i also think the reveiwer wants to address), in such cases, ABS-like behavior is NOT expected. If someone drives fast on slippy ground, a sudden brake will probably trigger ABS. But if the road condition is good and he is not driving very fast (or even slow), will ABS be expected? Definitely not. But that is what quite a lot drivers declaimed after accidents: stiff braking pedal (ABS-like behavior), the reason behind has been tallked a lot in Chinesed forums.

Here I would post some of these technical analysis, leave a comment if you think something is wrong. For those who can read Chinese, plz refer to the link 基于数据分析特斯拉事故原因. Since it's a long post, i would just put some conclusions.

View attachment 657722
In Ms. Zhang's case, given the data release by TESLA, after some simple calculation. The author has drawn a picture and he made comparisons among 3 parameters：cylinder pressure, ABS and the real acceleration. And he finds that cylinder pressure nearly matches ABS, however both differ a lot from real accelerations values.

In the first 2.5s before braking, cylinder pressure almost matches real accelerations values, after 2.5s, cylinder pressure increases rapidly, but the real accelerations values got limited, and within the key 1.8s after ABS' triggering, both the driver and ibooster have provided far more braking pressure than what the car's acceleration actually needed, but Tesla's ABS just output a small acceleration (~0.55g), which cannot even reach the standard threshold ( 0.9~1.1g ), this leads the final accident. Besides, there is no evidence that shows the road condition is bad. Since Tesla rewrites lots of software and logic of ibooster and low-level algorithm in ESC and high-level control algorithm. This part, especially how ABS control, Electromagnetic valve control, ESC, ibooster and regen get blended, probably should be responsible for this accident.

At this point, there is no need to confirm whether the calculation is right or not ( in fact a lot of analysis got almost similar results ), just focus on the above conclusions based on the calculation.
I'm not auto pro, but I'm an engineer, from above analysis i could personally not find obvious logic issues. So are the conclusions right?

For starters, are you confusing acceleration with deceleration here? As we've said, you cannot achieve the same amount of deceleration with ABS as you can with threshold braking. If the tyres are cold or on a low grip surface then ABS will reduce the rate of deceleration and increase the braking distance. Assuming your right hand scale is deceleration then this is exactly what the graph shows. As the car slows, the ABS causes the wheels to lock/unlock more than at higher speed so towards the end of the braking zone the deceleration rate is lower. That graph also needs to show vehicle speed to be any real use in determining what happened. My understanding is the driver was travelling above the speed limit. Perhaps that was a factor?

You say "In the first 2.5s before braking,". Clearly the brakes are being used before the 2.5 second mark but not hard enough.
The road surface, tyre type & condition, temperature, weather conditions etc. are all unknowns here (unless they are stated in Chinese and not translated) and that has a big effect on how well a car stops under heavy braking. You tell us conditions were good but how do you know if you weren't there? Does anyone have photographs of the accident scene? How do we know that piece of road wasn't covered in mud, or some spilled oil?
You say "standard threshold ( 0.9~1.1g )". If you mean that's the expected peak deceleration from a Model 3 well that would be under ideal conditions with the best tyres and braking as hard as possible.

There's nothing to see here. It's desperate grasping at straws to try and deflect blame away from the driver and onto someone or something else.

 

[skywalker2go]

For starters, are you confusing acceleration with deceleration here? As we've said, you cannot achieve the same amount of deceleration with ABS as you can with threshold braking. If the tyres are cold or on a low grip surface then ABS will reduce the rate of deceleration and increase the braking distance. Assuming your right hand scale is deceleration then this is exactly what the graph shows. As the car slows, the ABS causes the wheels to lock/unlock more than at higher speed so towards the end of the braking zone the deceleration rate is lower. That graph also needs to show vehicle speed to be any real use in determining what happened. My understanding is the driver was travelling above the speed limit. Perhaps that was a factor?

You say "In the first 2.5s before braking,". Clearly the brakes are being used before the 2.5 second mark but not hard enough.
The road surface, tyre type & condition, temperature, weather conditions etc. are all unknowns here (unless they are stated in Chinese and not translated) and that has a big effect on how well a car stops under heavy braking. You tell us conditions were good but how do you know if you weren't there? Does anyone have photographs of the accident scene? How do we know that piece of road wasn't covered in mud, or some spilled oil?
You say "standard threshold ( 0.9~1.1g )". If you mean that's the expected peak deceleration from a Model 3 well that would be under ideal conditions with the best tyres and braking as hard as possible.

There's nothing to see here. It's desperate grasping at straws to try and deflect blame away from the driver and onto someone or something else.

Thanks for the explanation, I think that sounds reasonable. If Tesla can conduct an experiment, that will eliminate doubts from the public.
Sorry for my poor translation. I indeed meant deceleration, but just forgot the term and thought of something like minus acceleration.
For other translation part, just try to grasp the main idea instead of details, especially auto-specific terms.

As for the good road conditions, that's what the author declaimed in the post, not by me. But as you mentioned, it still makes no sense, since it's not official statement by Tesla or the government.

According to what you described, I assume that you agree with the author's conclusions, only if his preset assumptions (especially road conditions) are right. Correct me if i misunderstood.

Next step I will keep an eye on the public info about road conditions in such cases, which may matter a lot. I think this will help to judge who is actually lying. The government has already taken actions, although no related info has been released yet. I think that should not take too long.
Really looking forward to the final report in China about Tesla. If that's in accordance with NHTSA's conclusion, will definitely buy one M3 myself. If not, that would also be a wonderful show the whole world willing to watch, right?

 

[Dangerous Fish]

I don't think Tesla is going to conduct any experiments when nothing is wrong with the sequence of events.
The author's conclusions are that the braking system is doing something abnormal when he tested it? No, I don't agree with that as I said before. I see nothing from the data from Ms. Zhang's case or the tester to think something is wrong with either car.

There are plenty of reports from drivers all over the world of Teslas behaving 'strangely' or 'abnormally' and in 99% of these cases it turns out the driver is either mistaken, doesn't understand how the car works or is trying to shift blame away from themselves. In the 1% of cases where there actually is a fault with the car, it is very obvious to see, usually without examining any data first. This example is not one of the 1%, it is driver error and the data supports that.

Here's a video which you might find useful, as it gives a little more insight into ABS and how tyres play a major part in how a Model 3 stops in an emergency.

 

[Krispykreme]

1. Bosch does not allow any automotive OEM to re-write or touch any of the software related to the brakes and ibooster. So that claim is totally false. Tesla can only modify how it sends command to the brake (interface).

2. ESC is totally different concept here. It’s triggered by yaw sensor/differential speed detected on 4 wheels. Highly unlikely that ESC has anything to do with this case.

3. All the data showed that between 118 to 94, the ibooster master cylinder isn’t under high pressure- which means the driver is simply not pressing hard enough. This is also evident on late triggering of ABS- because ibooster is also reading how deep and how fast the brake pedal is pressed before determining if ABS will be engaged.

based on three points above. The brakes is performing as it was designed to.

The other video has couple issues
1. Model 3 brakes is not vacuum based. Stiff pedal wouldn’t occur unless it has been through several panic cycle (this is mainly due to the fact that even though Bosch system is mainly brake by wire- it does maintain a mechanical linkage and does provide braking when ibooster electronic fail).

2. the comment is also wrong on re-gen braking. Re-gen braking is disengaged it does not mean the stop distance is longer. Because as driver you still have full use of brakes. It simply means you don’t have regen that is all.

what really is missing is the brake pedal position data.
But none of the data points for failure of brake system.

 

[Uncle Paul]

Tesla has evaluated this claim and does not agree with the young woman.

Read that she was passenger and her Father driving. They were driving about 50 mph over the speed limit.

Logs show the brakes being applied, but not firmly. The computer recognized the pressure was not going to be enough to avoid the accident, so increased the pressure to reduce the force of the imminent collision. It worked as designed, but was unable to totally prevent the collision.

Photographs of here standing on the display car show her wearing an entrance badge from a competitor China EV manufacturer.

She might be using activist tactics to persue monitory demands.

 

[SSonnentag]

Any small pothole or bump while braking can trigger ABS as well. This can give the FEELING of the car accelerating when in fact it is just decelerating more gradually.

 

[Dangerous Fish]

Oh look...

https://twitter.com/x/status/1393236861003264005