Model 3 brake system is not responding causing bumper-to-bumper accident slow speed

[yeahthatguy]

No, there isn't, you are assuming that's why the wheel/tyre configurator is there. It makes no difference to braking or ABS operation.

Then what is it for? You seem very confident in your understanding of the mechanics of this feature, but I cant find a detailed explanation anywhere. I have been told by service center employees it affects: the speedo calculation via the wheel speed sensors and ABS.

 

[buckets0fun]

No, there isn't, you are assuming that's why the wheel/tyre configurator is there. It makes no difference to braking or ABS operation.

Some have reported different ABS behavior on r compound tires. It’s not too far of a leap to think that winter tires would do the same.

 

[Dangerous Fish]

Then what is it for? You seem very confident in your understanding of the mechanics of this feature, but I cant find a detailed explanation anywhere. I have been told by service center employees it affects: the speedo calculation via the wheel speed sensors and ABS.

Some have reported different ABS behavior on r compound tires. It’s not too far of a leap to think that winter tires would do the same.

I'm not saying there isn't different ABS behaviour on different tyres. I'm saying the configurator doesn't have an effect on that.

 

[electrikar]

I do believe there is a possible ABS/brake modulation issue that folks may not be giving enough attention to. I have posted about this on here, and gotten feedback on the various tesla subreddits.

I experience the scenario multiple times a week in all weather conditions after swapping on my winter tires (Hakka R5's) where when applying more force than usual to the brake pedal (not standing the brakes by any means but not a leisurely braking event either) the brakes the will engage, then release slightly before reengaging to complete the stop. This does not change the pedal feel (does not go limp/to the floor, is not spongy, etc) but you can 100% feel the temporary increase in momentum before the brakes reengage. This makes the stopping experience have an elastic feel to it. The first few times it caused me a bit of concern as I was unsure when the brakes would reengage fully, however now that I experience it once to twice a week I've learned the time/distance it takes for them to reengage and its only a minor annoyance.

My belief is this is ABS assuming the tires are slipping more significantly, when in actuality its a softer winter compound that the ABS is not happy with. I have gone through and reset the learned wheel details on the car a few times to see if this would help and it has not appeared to. I have put roughly 2,500 miles on the Hakka's since I put them on, which one would assume is more than enough for both the car to calibrate and for the compound in contact with the road surface to be free of manufacturing/install grime.

I run the MPP brake booster brace (and have since the car was new) I routinely check the rotors and have done the brake burnishing process in the service menu. I do not believe this is a hardware issue. I have considered getting a draggy or one of the CANbus monitoring tools to see if I can successfully record a change in G force during these events but I'm also a month or so out from swapping back on some high performance summer tires which very well could alleviate the issue.

Sounds like a brake booster issue. That's how brakes could feel when vacuum assist is lost

Odd. If the brake pedal lit up, as you say, in 6, how would you know? Were you looking at your display?

Honestly, this sounds like a situation where you pressed the accelerator and not the brake, while under AP.

Yes. I meant "brake pedal". sorry guys. Thanks for all the feedback. I did look at the brake pedal since it does not stop. If I did press the accelerator it would have been a big accident.

 

[electrikar]

Sounds like a brake booster issue. That's how brakes could feel when vacuum assist is lost

Odd. If the brake pedal lit up, as you say, in 6, how would you know? Were you looking at your display?

Honestly, this sounds like a situation where you pressed the accelerator and not the brake, while under AP.

Honestly, If I did press the accelerator, it will cause even bigger accident and I did make sure that my right feet was pressed on the right pedal. The Tesla safety engineer is looking at recording as well. They would have pointed it out.

 

[Gauss Guzzler]

The car has a feature called "Obstacle Aware Acceleration" intended to prevent serious damage in the event of an accidentally depressed Gauss pedal. So it's absolutely possible that you pushed the pedal to the floor, hence the firm feeling, but yet the car only gently accelerated because it detected the car ahead.

What's not possible, however, is a complete brake system failure that is intermittent and/or difficult to reproduce. So if they don't find some obvious catastrophic failure within the first few seconds of evaluating the car, then it's certain that you hit the wrong pedal.

 

[LoL-Gas]

What tires are you running on the car? My model 3 has this weird brake loss when going from regen to friction brakes; also does some weird lunging forward when getting off hard braking and switching back to regen. This only happens with winter tires...

 

[mrfiat74]

Can't Tesla look at the logs from the car and tell exactly which pedal he was pressing when the accident occurred?

 

[stopcrazypp]

Can't Tesla look at the logs from the car and tell exactly which pedal he was pressing when the accident occurred?

Given it was a minor bump it may not have recorded it in the EDR (as it would seem none of airbags went off, nor seat belt tensioners activated). OP would have to identify the exact day and time and see if other logs have it recorded, but it may still be very hard to pin down the exact point.

 

[electrikar]

The car has a feature called "Obstacle Aware Acceleration" intended to prevent serious damage in the event of an accidentally depressed Gauss pedal. So it's absolutely possible that you pushed the pedal to the floor, hence the firm feeling, but yet the car only gently accelerated because it detected the car ahead.

What's not possible, however, is a complete brake system failure that is intermittent and/or difficult to reproduce. So if they don't find some obvious catastrophic failure within the first few seconds of evaluating the car, then it's certain that you hit the wrong pedal.

It is possible. definitely the break padal does act firm and the slowly move forward and it does detect the car in front of me . I have no way do a complete stop to prevent an accident

 

[KenC]

Well, it's very difficult to understand what happened. Can you post a picture of the minor damage?

"1. Trying to merge to the left lane ( one of the two left lanes)" Okay, that seems clear enough.

"2. Because of the traffic ( car in front of )- I could not merge, and I was asking people to let me merge in" Okay, seems fairly clear, though it's not clear how you were "asking", were you waving your arm out your window, or was it just your blinker?

"3. I can merge only half of the car to the left lane" Okay, so you're straddling the lane line?

"4. I am in the middle of two-lane ( the divider line is in front of me - the car may try to change / correct to the correct lane )" Again, it seems like you're straddling the lane line, but why do you think the car "may try to change/correct"? You're in control right? AP is not on right? The car may give you a proximity warning, but why do you think it will correct, and what do you think that means?

"5. My car is getting close (moving) to the car in from of me - really slow speed" Okay, so you are slowly wedging/forcing yourself into the left lane, but you're very close to the car in front. This is not uncommon in heavy backed-up traffic.

"6. I am trying to push the break paddle - the break pad got tight up and did not respond to my force of pressing the paddle
7. the car keep moving and hit the car in front of me" Everything seems okay up to this point, but now, it gets confusing. This is the critical point where something is not right. Were you able to save the video from this moment where you hit the car in front? It's extremely unusual and rare, if not seemingly impossible to press the brake pedal and have the car keep moving and hit the car in front.

Was your left foot stuck under the brake pedal, while you were pushing it with the right? How did you have time to actually look at your foot on the brake pedal? If a Tesla engineer is looking at the data, it will take them no time at all to tell which pedal was actually being pushed.

"It is possible. definitely the break padal does act firm and the slowly move forward and it does detect the car in front of me . I have no way do a complete stop to prevent an accident"

Again, this should be an impossibility, unless you have something stuck under the brake pedal, preventing you from completely pressing it. I would contact the Tesla engineer looking at the data, he should have an answer, immediately.

 

[arghx7]

driver error

 

[XPsionic]

Well, it's very difficult to understand what happened. Can you post a picture of the minor damage?

"6. I am trying to push the break paddle - the break pad got tight up and did not respond to my force of pressing the paddle
7. the car keep moving and hit the car in front of me" Everything seems okay up to this point, but now, it gets confusing. This is the critical point where something is not right. Were you able to save the video from this moment where you hit the car in front? It's extremely unusual and rare, if not seemingly impossible to press the brake pedal and have the car keep moving and hit the car in front.

With regen braking, just lifting off the accelerator should've caused the car to stop in a few feet at slow, bumper to bumper kind of speed. If brake pedal was pressed, that + regen will stop the car almost immediately from say, 5mph.

To feel a firm pedal + the car not stopping + cannot repeat the same experience afterwards... I'd say it is more likely than not that OP pressed onto the accelerator pedal by accident with object aware acceleration turned on, minimizing the speed and damage.

 

[rrolsbe]

When my 2018 Model 3 Performance was new, I had one incident when leaving home (on a slight downhill) where I discovered suddenly that the power brakes were not working. It caught me by surprise as I tried to use the brakes to slow down while going down the hill. If something would have been in front of me, I probably would have hit it because the overall feel was "No brakes", but I pushed VERY hard and got the car to slow down a little bit. So, yes, basic braking was working but the pressure on the pedal was something like 100x to get anything out of it.

I turned around in the next intersection and went back up to home and parked the car at the curb in front of my house ( and there was still no power brake action). I turned the issue into service and they went over the car remotely. They didn't really tell me much of anything but had me try the car again later and the brakes were working okay at that point. Still not sure what happened, but it never happened again...

So I know the feeling, OP. My first reaction was that the brakes were not working, but I really pressed about as hard as I could and was able to get a little bit of slowing. Could have been a scary situation if it would have occurred later in my drive at higher speed.

The Model 3 does not have vacuum available for brake boost it uses a 12VDC motor located inside the master cylinder for the boost function. If you have no boost and regen is very limited for some reason, it can take a LOT of force to stop a heavy car. See this video for more info

 

[zoomer0056]

No need to use brake peddle at such low speeds. Just foot off the accelerator will "hold" the car still. OP must've had pressure on accelerator. We'll see how the Service Center responds.

 

[comanchepilot]

The OP 'could' have had CREEP on - not HOLD. If you have creep on it will act like an ICE vehicle with an automatic transmission and creep into the car in front.

If he was pressing the brake pedal - maybe he wasn't pressing enough - perhaps just resting his foot on the brake. None of us were there - and yes - Tesla can download the data and see whats up - even most ICE vehicles now have event recorders.

 

[enemji]

What stopping mode was the car in? I'm guessing creep or roll, not hold?

 

[KenC]

The OP 'could' have had CREEP on - not HOLD. If you have creep on it will act like an ICE vehicle with an automatic transmission and creep into the car in front.

If he was pressing the brake pedal - maybe he wasn't pressing enough - perhaps just resting his foot on the brake. None of us were there - and yes - Tesla can download the data and see whats up - even most ICE vehicles now have event recorders.

Maybe, but the OP said he even looked to make sure he was pressing the pedal! It's weird, but the OP has not returned, so, who knows, but I'm betting on human error.

 

[afadeev]

Maybe, but the OP said he even looked to make sure he was pressing the pedal! It's weird, but the OP has not returned, so, who knows, but I'm betting on human error.

I've been in a few near accidents, and one actual accident in my driving life.
At no time was I actually staring at the brake pedal in the midst of an event. You ALWAYS have something more important to worry about, like looking for an escape path out of a situation, or a way to avoid a collision. Or watching an absent-minded idiot aim for your rear bumper in the rear view mirror and bracing for an impact.

NEVER ever have I looked at my brake pedal. And I did experience a few brake fade events at the end of a front straight on track.

Too many things don't add up in OPs story.
Doesn't matter either way.

 

[KenC]

I've been in a few near accidents, and one actual accident in my driving life.
At no time was I actually staring at the brake pedal in the midst of an event. You ALWAYS have something more important to worry about, like looking for an escape path out of a situation, or a way to avoid a collision. Or watching an absent-minded idiot aim for your rear bumper in the rear view mirror and bracing for an impact.

NEVER ever have I looked at my brake pedal. And I did experience a few brake fade events at the end of a front straight on track.

Too many things don't add up in OPs story.
Doesn't matter either way.

Yes, I found the notion of having the time to look at one's foot on the brake pedal odd, to say the least. But, I find lots of driver behaviors by others to be odd. I wasn't there, and it sounds like the OP was going very slowly trying to merge into the left, so perhaps he did have the time to glance down to see if his foot was in the right place.