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Hard braking with TACC in stop-n-go traffic

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Even 1 leaves a lot of space. I hate to think where 7 or 4 would leave you!

Agreed. I only use 1, and I think it still leaves far too much room, especially when accelerating in stop-and-go traffic. I have to press the pedal to catch up or one or two cars jump in front.​

On 17.42 I have noticed ‘late braking’ where it seems to sometimes acquire the car in front late and then have to brake late to stop in time.

This is frustrating. I had to disengage the other day when the car was speeding up to an intersection full of stopped vehicles. The car does not seem to notice stopped cars soon enough. This inability to see ahead sometimes causes late and aggressive braking.​

I’ve experienced exactly what you describe and I think it’s the brake pedal “juddering” (for lack of a better word.)

I believe many of us agree that this is what is happening. The break pedal's rapid engagement and disengagement sequence makes a noise that sounds as though something is loose in the front-end. I experienced this with a 2014 loaner months ago as well as with my MS on 2017.34 2448cfc.​
 
The tires are brand new. The car is only 2 months old. I did try an emergency stop yesterday on my own and this sound did not occur. I think it's something with TACC specifically.

Ok, that's interesting. I would have bet it was the ABS. Uploading video would probably be pretty hard, since it doesn't always happen, right? I would take it to the SC, this is definitely nothing you can fix. It still sounds like it's an ABS problem, but maybe the car thinks wheel spin is happening, when it isn't?

I'd still say it's brake sensor issue. SW should not act out on a single car. And I am pretty sure it isn't the AP either, since it doesn't seem to be just a very violent brake, like it would if it would have some issues recognizing cars until they are too close. Has this sound ever happened under normal braking?
 
I think, collectively, we have possibly found the reason for the noise and you have summed it all up nicely. When I'm at the SvC tomorrow I will discuss this theory with them and see what they say.

Hey sevenout! I posted something similar a few weeks back and have yet to find any solution. Same exact sound & situation and my MS is about a month old as well!! I asked the SC about it and have had no luck. Thread below:

Autopilot seems to love using ABS...

Same struggles, and have been meaning to catch it on video (unfortunately my MS is now in service due to the recent madness with the "Parking Break Needs Service" error that some fortunate new owners have run into).

I have been unable to recreate the sound without TACC being enabled, it only ever occurs with TACC enabled and will occur primarily in Stop & Go Traffic, however really anytime TACC brakes firmly due to it getting "scared" or if a car jumps into my lane, etc..

I am supposed to pick up my MS from the SC tomorrow, I plan on taking them on a test drive to show them the sound and see what they think.
 
Here are some videos I took where I was able to capture the sound.

#1 - You can hear the sound just as the speedometer hits 12mph. It's very short but that's when TACC decided it needed to hard brake due to the traffic in front of me coming to a stop.

#2 - This one is very short but you can clearly hear the loud judder of the brake pedal. This is a stop-n-go event. Start at zero and go up to 2mph and then hard brake back to zero.

#3 - This one is where AP had drifted way too close to the left of the lane and was starting to encroach on the traffic to my left. Eventually TACC had to hard brake just as the proximity alarm chimed. The camera moves around a bit because I was worried I was going to have to take over due to how close I was getting to the cars on my left.
 
Here are some videos I took where I was able to capture the sound.
Excellent job with capturing the event. That sound is almost certainly the brake pedal moving abruptly.
The first video sounds like mine does, and others I've driven.
The second, and especially the third video sound way more abnormal and aggressively repetitive in nature; like as if it's changing it's mind completely, over a half dozen times, in a matter of milliseconds. I would not consider this to be normal.
 
And it's also harder on the brake pads. I notice this with AP as well. Gone are the days when after a few years, there would be hardly any brake wear on the callipers, now with AP and and TACC, the pads wear out more which means Tesla makes more when you bring the car in for replacement of the brakes!
 
Has anyone else experienced hard braking by TACC during stop-n-go traffic? For me, this started with 2017.34 and has persisted with 2017.40.1. As cars begin to slow to a stop, the car will suddenly hard brake and come to a stop. I'm only going maybe 1-2 MPH when this happens but it is abrupt when it does. It does not happen every time either. Half of the time it comes to a nice smooth stop. Also, when it does hard break, I also hear a fairly loud machine gun like sound coming from the front of the car. Could this be ABS? Have never heard that sound before except when this happens. Not sure if I should schedule a service call.

I can confirm that mine is doing this now with the last two update. I use it almost daily in stop-and-go.
 
I just dropped my car off at the SvC today to have them look into this. They seemed to indicate that it has something to do with ABS. I guess we'll see what they find after I get the car back.

I just got mine back yesterday, test drove it with the SvC Lead Tech, and received a call today that the noise is "Normal" and it is the Brake's being applied in a quick pulsing action (Not ABS) but rather a function of TACC.

Supposedly they checked with Engineering, and other Tech's at Tesla and were informed that it is Normal. Very curious if you hear something different from you SvC. The noise, and pulsing function is odd, and would certainly seem like something that would wear the brakes down significantly over a short time.
 
Just to throw in my 2 cents I have found that TACC is actually not as useful as it once was when I first got my car with regards to stop and go traffic. It will either accelerate too late, causing it to have to slow down faster than it needs to when it finally detects the car in front of it or with Autosteer engaged at low speeds my car will 'dance' around the lane and sometimes drift over into other lanes.
 
I just got mine back yesterday, test drove it with the SvC Lead Tech, and received a call today that the noise is "Normal" and it is the Brake's being applied in a quick pulsing action (Not ABS) but rather a function of TACC.

Supposedly they checked with Engineering, and other Tech's at Tesla and were informed that it is Normal. Very curious if you hear something different from you SvC. The noise, and pulsing function is odd, and would certainly seem like something that would wear the brakes down significantly over a short time.
Mine has been at the SvC since Thursday. The tech seemed to indicate that ABS was involved and that it was probably normal. Later after dropping it off I got a text from the SvC that they were ordering a front strut and would get back to me with an ETA. That’s all I know right now.
 
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Mine has been at the SvC since Thursday. The tech seemed to indicate that ABS was involved and that it was probably normal. Later after dropping it off I got a text from the SvC that they were ordering a front strut and would get back to me with an ETA. That’s all I know right now.

Thanks for the update!! I have to take mine back into the SvC tomorrow due to them botching a repair job on one of the window seals. Do you have any further information I could possibly throw at them or are you still awaiting more info?
 
Thanks for the update!! I have to take mine back into the SvC tomorrow due to them botching a repair job on one of the window seals. Do you have any further information I could possibly throw at them or are you still awaiting more info?
I just got my car back tonight. I haven't had it long enough to be able to test if the repairs they did actually fixed anything. Hopefully tomorrow I'll be able to test that. The main thing they did was:

Corrections: Spring and Damper Assembly - Front - RH
replaced the Spring and Damper Assembly - Front - RH
FRONT COIL SUSPENSION MODULE - DM - Qty 1
S2 (1030607-01-D)
Parts Replaced or Added

Corrections: Spring and Damper Assembly - Front - LH
replaced the Spring and Damper Assembly - Front - LH
FRONT COIL SUSPENSION MODULE - DM - Qty 1
S2 (1030607-01-D)
Parts Replaced or Added

The tech said that they basically replaced the whole front suspension.

When I dropped the car off to have the problem looked at, I emailed them the links to those videos above. They seemed happy to get them.
 
I just got my car back tonight. I haven't had it long enough to be able to test if the repairs they did actually fixed anything. Hopefully tomorrow I'll be able to test that. The main thing they did was:

Corrections: Spring and Damper Assembly - Front - RH
replaced the Spring and Damper Assembly - Front - RH
FRONT COIL SUSPENSION MODULE - DM - Qty 1
S2 (1030607-01-D)
Parts Replaced or Added

Corrections: Spring and Damper Assembly - Front - LH
replaced the Spring and Damper Assembly - Front - LH
FRONT COIL SUSPENSION MODULE - DM - Qty 1
S2 (1030607-01-D)
Parts Replaced or Added

The tech said that they basically replaced the whole front suspension.

When I dropped the car off to have the problem looked at, I emailed them the links to those videos above. They seemed happy to get them.

Thanks for the update! I hope that fixed the problem for you so I can ask my SvC to do the same!! :)
 
Same TACC breaking sound since I got the car in Dec 2016. Used to think it was ABS but lately was convinced it was somewhere in the TACC pulling the break pedal mechanism. Told service center about it but they couldn’t figure it out. Those videos are very helpful. Got a 2015 P85 loaner earlier this week and it did not have the sound under similar conditions.