Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.
Register
  • The final cut of the 9th episode of the Tesla Motors Club Podcast, featuring Chad Schwitters, the former president of Plug In America, is now available. You can watch it now on YouTube or listen to it on all major podcast networks.

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

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
 
Never had any such problem in dry, wet, or snowy conditions. We also haven't seen logs from the accident in China so who knows. I'm sure the Chinese government has already seen them and is making a determination of what to do next.
Thank you for the information. I am curious to see the logs too. But if it is a software issue, will it be logged? It's all over the social media now, the government is stepped in. So I am intended to wait for the results before picking up my M3...
 
We don't know all the parameters that are logged in the event of the crash. They may be able to get a full set of outputs from the Bosch braking module, which will help diagnose if something is wrong with it. Even if they don't, they likely have a lot of basic parameters. For example, the accident in question could be something stupid like the driver hit the gas pedal instead of the brake. They would at least have accelerator pedal position and brake activity.
 
When the iBooster fails, you will most likely see an orange brake warning, as well as a "Power braking assist reduced" error. This means the system *thinks* the iBooster has failed (i.e. not purposefully reducing the booster power in favor of regen braking). I have not read any report of the brake pedal being stiff without any error/alert present.

IMO the lady involved in the accident should've taken a picture of the Notifications screen which shows a list of recent errors (of course, assuming the car still worked and she was not incapacitated). This would've given her much stronger evidence to argue against Tesla.

Like people said in other posts, brake booster failures happen on all cars, so there is always risk. I don't know if it's a Bosch issue. Might worth investigating whether other cars fitted with the iBooster also experience similar failures.
 
We don't know all the parameters that are logged in the event of the crash. They may be able to get a full set of outputs from the Bosch braking module, which will help diagnose if something is wrong with it. Even if they don't, they likely have a lot of basic parameters. For example, the accident in question could be something stupid like the driver hit the gas pedal instead of the brake. They would at least have accelerator pedal position and brake activity.
Agreed. More info is needed.
 
When the iBooster fails, you will most likely see an orange brake warning, as well as a "Power braking assist reduced" error. This means the system *thinks* the iBooster has failed (i.e. not purposefully reducing the booster power in favor of regen braking). I have not read any report of the brake pedal being stiff without any error/alert present.

IMO the lady involved in the accident should've taken a picture of the Notifications screen which shows a list of recent errors (of course, assuming the car still worked and she was not incapacitated). This would've given her much stronger evidence to argue against Tesla.

Like people said in other posts, brake booster failures happen on all cars, so there is always risk. I don't know if it's a Bosch issue. Might worth investigating whether other cars fitted with the iBooster also experience similar failures.
The lady in the accident doesn’t mentioned error messages. In the other case(hitting a wall), I don’t think the driver mentioned error message neither. I don’t worry about brake booster system failure, like you said, could happened to every car. I am worried about the braking system setting/logic, reducing booster power in favor of regen brake. Not sure if it’s real. If it is, it would be a stupid setting, and safety issue.
 
When the iBooster fails, you will most likely see an orange brake warning, as well as a "Power braking assist reduced" error. This means the system *thinks* the iBooster has failed (i.e. not purposefully reducing the booster power in favor of regen braking). I have not read any report of the brake pedal being stiff without any error/alert present.

IMO the lady involved in the accident should've taken a picture of the Notifications screen which shows a list of recent errors (of course, assuming the car still worked and she was not incapacitated). This would've given her much stronger evidence to argue against Tesla.

Like people said in other posts, brake booster failures happen on all cars, so there is always risk. I don't know if it's a Bosch issue. Might worth investigating whether other cars fitted with the iBooster also experience similar failures.
BTW, some people claimed that it’s not Bosch issue, it’s a Tesla issue, since Tesla writes its own code, instead of using Bosch’s.
 
I am worried about the braking system setting/logic, reducing booster power in favor of regen brake. Not sure if it’s real. If it is, it would be a stupid setting, and safety issue.

The author of this investigation report "Tesla Regen, Brakes, and Sudden Acceleration" claims the friction braking and regen braking on Teslas are separate (with the possible exception of RWD models).
 
Last edited:
  • Like
Reactions: Msjulie

stopcrazypp

Well-Known Member
Dec 8, 2007
12,032
7,823
The author of this investigation report "Tesla Regen, Brakes, and Sudden Acceleration" claims the friction braking and regen braking on Teslas are separate (with the possible exception of RWD models).
While the paper referenced has a lot of the useful information to reference, I would caution about fully believing the overall theory that it pushes. The NHTSA ODI seems to disagree with it:
"As part of its evaluation of DP20-001, ODI reviewed two defect theories alleging vehicle-based causes of SUA in the subject vehicles. Both theories were developed by Dr. Ronald Belt, the first in 2018 and the second in 2020. A paper describing the most recent theory was submitted to NHTSA by the petitioner and is based upon Dr. Belt’s review of EDR data from the crash reported in VOQ 11206155. The other theory was referenced by the consumer who submitted VOQ 11206155 and is based upon Dr. Belt’s third-hand reconstruction of log data from an unknown SUA event. Both papers are based upon incorrect event data, incorrect reconstructions of event dynamics, and false assumptions regarding vehicle design factors."
https://static.nhtsa.gov/odi/inv/2020/INCLA-DP20001-6158.PDF

Note that in general, Tesla does not blend regen brakes into the brake pedal in the traditional sense (as hybrids do). The way hybrids do it is by when you press the brakes, the system gives x-amount of regen along with it (to net to the expected braking force). Lifting off the accelerator pedal does not provide regen braking, only pressing the brake pedal.

The regen in Teslas instead is 100% controlled by the lifting off the accelerator pedal. However the braking system still has to do some blending even in this case (to not interfere with each other).
 
Last edited:
The regen in Teslas instead is 100% controlled by the lifting off the accelerator pedal. However the braking system still has to do some blending even in this case (to not interfere with each other).
Why would it? Lift off accelerator fully and you get maximum regen. If you need additional stopping power then apply friction brakes like any other car. It's not like downshifting an ICE or using a jake brake requires that info to be fed to the braking system.

I could be wrong, but as far as I know there is zero blending of regen and friction brakes on a Tesla and the entire premise of this thread is off base.
 

stopcrazypp

Well-Known Member
Dec 8, 2007
12,032
7,823
Why would it? Lift off accelerator fully and you get maximum regen. If you need additional stopping power then apply friction brakes like any other car. It's not like downshifting an ICE or using a jake brake requires that info to be fed to the braking system.

I could be wrong, but as far as I know there is zero blending of regen and friction brakes on a Tesla and the entire premise of this thread is off base.
The article linked (which as mentioned may not necessarily be correct) suggests there there is some interaction of regen with the ABS and ESC systems that must be accounted for by various regulations in the US and EU. The regen force is stronger than typical ICE engine braking (as such there also brake light actuation requirements which interacts with the braking system).

Reading it more closely that article does suggest there is no "blending" per se among the braking and regen at least for the AWD versions. The RWD versions might have it however, due to the regen only applying to rear wheels and the weight shifting to the front may require the braking system to brake the front wheels to compensate (otherwise it may be unstable). AWD (or FWD) does not have this same problem as they have regen available in the front wheels.
 
All I can add to the conversation is that I've been following everything Tesla on this and other forums for 5 years and have not seen any mention of the specific failure mentioned by OP. I have also owned a RWD Model 3 LR for 3 years and 60k miles and have not encountered the specific failure in wet, ice, snow, or loose gravel. Not have I read about anyone else having the same failure on their Model 3.
 
  • Like
Reactions: Big Earl

stopcrazypp

Well-Known Member
Dec 8, 2007
12,032
7,823
All I can add to the conversation is that I've been following everything Tesla on this and other forums for 5 years and have not seen any mention of the specific failure mentioned by OP. I have also owned a RWD Model 3 LR for 3 years and 60k miles and have not encountered the specific failure in wet, ice, snow, or loose gravel. Not have I read about anyone else having the same failure on their Model 3.
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.
 
Last edited:

stopcrazypp

Well-Known Member
Dec 8, 2007
12,032
7,823
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!!!).
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
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.
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!

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 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.
 
Last edited:
Note that in general, Tesla does not blend regen brakes into the brake pedal in the traditional sense (as hybrids do). The way hybrids do it is by when you press the brakes, the system gives x-amount of regen along with it (to net to the expected braking force). Lifting off the accelerator pedal does not provide regen braking, only pressing the brake pedal.
Name checks out.

The Bosch iBooster system does do blending anytime it's useful. For example when regen is limited by a cold or full battery the cruise control will seamlessly use the brakes earlier, or if low regen was selected in previous software revs the brake pedal would always increase regen before actually engaging the pads. This intervention is part of the reason some people complain about the feel of the brakes.

So of course it's possible that some 1-in-a-million glitch could cause a brake malfunction but the odds are literally 1 in a million at this point. Meanwhile, don't get too caught up in the hype - recall that Tesla's are the least likely cars to catch fire and Toyota/Lexus are the least likely to have unintended acceleration, despite everything the media has led you to believe.

@stopcrazypp thanks for posting those videos but I don't understand what's being shown. It looks like some idiot is just driving over a curb for no reason. Was he trying to show that the forward collision system isn't well tuned for greased ice or whatever that surface was?
 
Last edited:

stopcrazypp

Well-Known Member
Dec 8, 2007
12,032
7,823
Name checks out.

The Bosch iBooster system does do blending anytime it's useful. For example when regen is limited by a cold or full battery the cruise control will seamlessly use the brakes earlier, or if low regen was selected in previous software revs the brake pedal would always increase regen before actually engaging the pads. This intervention is part of the reason some people complain about the feel of the brakes.

So of course it's possible that some 1-in-a-million glitch could cause a brake malfunction but the odds are literally 1 in a million at this point. Meanwhile, don't get too caught up in the hype - recall that Tesla's are the least likely cars to catch fire and Toyota/Lexus are the least likely to have unintended acceleration, despite everything the media has led you to believe.

@stopcrazypp thanks for posting those videos but I don't understand what's being shown. It looks like some idiot is just driving over a curb for no reason. Was he trying to show that the forward collision system isn't well tuned for greased ice or whatever that surface was?
You can google translate the article for more details:
Google Translate

The guy in the video is a Tesla rep who met with the customer to try to reproduce the braking problem at the location with wet/sandy conditions. The first try the Tesla rep was able to stop as you see in the video. The second time, the other guy and lady told him to pump the brakes two times before braking fully and the Tesla rep crashed. Apparently this was with a different Model 3 (not the customer's).

The internet seems to be saying Tesla's braking system is defective as a result. However from the other video I linked it's obvious that pumping the brakes would increase the stopping distance, and given the guy only stopped just barely with the first brake, the action of pumping the brakes can easily be the reason why the car crashed (nothing to do with the system).
 
Last edited:
  • Like
Reactions: android04
While the paper referenced has a lot of the useful information to reference, I would caution about fully believing the overall theory that it pushes. The NHTSA ODI seems to disagree with it:
"As part of its evaluation of DP20-001, ODI reviewed two defect theories alleging vehicle-based causes of SUA in the subject vehicles. Both theories were developed by Dr. Ronald Belt, the first in 2018 and the second in 2020. A paper describing the most recent theory was submitted to NHTSA by the petitioner and is based upon Dr. Belt’s review of EDR data from the crash reported in VOQ 11206155. The other theory was referenced by the consumer who submitted VOQ 11206155 and is based upon Dr. Belt’s third-hand reconstruction of log data from an unknown SUA event. Both papers are based upon incorrect event data, incorrect reconstructions of event dynamics, and false assumptions regarding vehicle design factors."
https://static.nhtsa.gov/odi/inv/2020/INCLA-DP20001-6158.PDF

Note that in general, Tesla does not blend regen brakes into the brake pedal in the traditional sense (as hybrids do). The way hybrids do it is by when you press the brakes, the system gives x-amount of regen along with it (to net to the expected braking force). Lifting off the accelerator pedal does not provide regen braking, only pressing the brake pedal.

The regen in Teslas instead is 100% controlled by the lifting off the accelerator pedal. However the braking system still has to do some blending even in this case (to not interfere with each other).
Thank you very much for the detailed explanation. Hope it is working in the non-blending (or less blending) way. I would feel more comfortable that way.
 
All I can add to the conversation is that I've been following everything Tesla on this and other forums for 5 years and have not seen any mention of the specific failure mentioned by OP. I have also owned a RWD Model 3 LR for 3 years and 60k miles and have not encountered the specific failure in wet, ice, snow, or loose gravel. Not have I read about anyone else having the same failure on their Model 3.
Thank you for the reply. That’s my feeling too, after a quick search online. If it is a software issue, it would not be an specific MIC M3 issue, unless Tesla pushes different OTA for different regions?
 

Products we're discussing on TMC...

About Us

Formed in 2006, Tesla Motors Club (TMC) was the first independent online Tesla community. Today it remains the largest and most dynamic community of Tesla enthusiasts. Learn more.

Do you value your experience at TMC? Consider becoming a Supporting Member of Tesla Motors Club. As a thank you for your contribution, you'll get nearly no ads in the Community and Groups sections. Additional perks are available depending on the level of contribution. Please visit the Account Upgrades page for more details.


SUPPORT TMC
Top