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Traffice-Aware Cruise Control Question

jaywar

Member
Sep 17, 2020
24
4
Unknown
I have searched the forums and not finding the answer(s) I am looking for. So I hope someone knows here.

I am wondering when the M3 is in TACC, when it slows down, does it apply the brakes 100% or does it use regenerative braking to slow down most of the time? I have watched the brake pedal move as it slows down (while in the passenger seat with the wife driving). Seems like a negative if it's using the brakes versus regen. Are there any articles on this? I would rather just do one-pedal driving then use this feature in heavy traffic.
 

HankLloydRight

No Roads
Supporting Member
Jan 18, 2014
13,070
11,321
Connecticut
I'm not sure I understand your concern? It uses both. But why does it matter? TACC is a great feature to have no matter how the car decides to slow itself down.

I would rather just do one-pedal driving then use this feature in heavy traffic.

With TACC, it's "no pedal driving". You still steer (unless you go into Autopilot/Autosteer mode), but in TACC, you don't use the brake or accelerator at all.
 

jaywar

Member
Sep 17, 2020
24
4
Unknown
I'm not sure I understand your concern? It uses both. But why does it matter? TACC is a great feature to have no matter how the car decides to slow itself down.



With TACC, it's "no pedal driving". You still steer (unless you go into Autopilot/Autosteer mode), but in TACC, you don't use the brake or accelerator at all.

So I understand what TACC does (had adaptive cruise control in Subaru Forester with Eyesight) and is a nice feature. My concern or question was, does it use 80/90/100% etc., of the brakes or does it decelerate/regen to slow down/stop? I ask because I saw the brakes being applied when it slowed down. Supposedly one-pedal driving is using regen 100% and applying brakes to stop and hold? If TACC is using more brakes then regen, I'd rather one-pedal drive so the brakes don't wear as much. This is our first Tesla and love the car.
 

HankLloydRight

No Roads
Supporting Member
Jan 18, 2014
13,070
11,321
Connecticut
I'd rather one-pedal drive so the brakes don't wear as much. This is our first Tesla and love the car.

Honestly, I really wouldn't worry about it! The brakes already last a lot longer than an ICE vehicle. The difference of the additional brake wear from TACC is marginal, at best. Certainly not worth the hassle of not using TACC at all.
 

JulienW

Active Member
Jul 7, 2018
2,737
3,310
Atlanta
It would be the amount of G-Forces needed to slow the car. It will just like you letting off accelerator and regen will kick in. If you or TACC needs to decelerate more than regen then you or TACC will start applying friction. Also regen continues while using the friction brakes (you or TACC) so the amount needed will be much less than a traditional ICE.
 

jaywar

Member
Sep 17, 2020
24
4
Unknown
So I was able to take the M3 out this evening after my wife got home and was using TACC. Had my foot barely touching the brake pedal and it wouldn’t depress until it was at a stop and was using regen to slow. So I was able to confirm and answer my own question :)
 

Joe19812

Member
Jul 20, 2019
11
8
Phoenix
I have searched the forums and not finding the answer(s) I am looking for. So I hope someone knows here.

I am wondering when the M3 is in TACC, when it slows down, does it apply the brakes 100% or does it use regenerative braking to slow down most of the time? I have watched the brake pedal move as it slows down (while in the passenger seat with the wife driving). Seems like a negative if it's using the brakes versus regen. Are there any articles on this? I would rather just do one-pedal driving then use this feature in heavy traffic.
Look at the horizontal bar below the speed display. When it slows down if the bar is green then it’s in regen.
 

Saghost

Well-Known Member
Oct 9, 2013
8,224
7,088
Delaware
It uses both, depending on conditions and deceleration rates, prioritizing regen where possible. At least my X does, and I would assume the 3 does the same.

If you're feeling particularly brave, you can slide a foot slightly under the brake pedal and feel when the car applies the brakes - the iBooster system Tesla uses is basically a motor acting directly on the master cylinder piston, so the car pulls the pedal down in the process of applying the brakes. This is of course somewhat risky, as it may affect your ability to apply the brakes in an emergency.
 

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