# Friction braking and TACC



## ig0p0g0 (Apr 27, 2018)

Sort of software and hardware, but I think more software.

I'm going to assume that TACC uses regen braking whenever possible.

In slow traffic and close distance, I imagine it's a lot of friction braking. Sometimes I can definitely feel the friction braking if the car in front goes from slow to zero quickly.

My question...is there any indicator that shows when friction braking is used? Not just black or green line, I understand that. I'd like to get some sense of whether my manual driving is more efficient than tacc in these situations.

On a tangent, is it safe to use tacc to go down a long, steep grade? Willl you know if the pads are overheating? I don't like to suddenly find out that I have no brakes. Tangent to the tangent, I've read about folks knowing their brake temperature, where is that info?

Thanks!


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## msjulie (Feb 6, 2018)

This relates to regular old cruise control - but my experience with it on moderate slops is it uses regen as needed; never was < 20mph with it but I have seen regen, weakly, even at low speeds fwiw


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## PNWmisty (Aug 19, 2017)

ig0p0g0 said:


> I'm going to assume that TACC uses regen braking whenever possible.
> 
> In slow traffic and close distance, I imagine it's a lot of friction braking. Sometimes I can definitely feel the friction braking if the car in front goes from slow to zero quickly.


My experience has been TACC uses regenerative braking exclusively unless friction braking is needed to avoid a collision and that would not be a normal situation. It will use friction braking from about 5 mph to a stop.



> On a tangent, is it safe to use tacc to go down a long, steep grade? Willl you know if the pads are overheating? I don't like to suddenly find out that I have no brakes.


I've been on some very steep grades and regenerative braking was more than enough to maintain descents much slower than I wanted to go. The only way I think this would not be the case is if your battery was near 100% charge and regen was temporarily unavailable or you were loaded over the vehicles maximum GVWR and the grade was unusually steep.

As to how you would know if your brakes were over-heating, it would be the same way as with any car, you would notice decreased brake performance and the need for more brake pedal pressure.


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## ig0p0g0 (Apr 27, 2018)

Thanks! Your answer to the first two questions made the third irrelevant, but that was exactly my point - if you are not the one doing the braking, you won't notice that squishy decreased performance feeling until maybe it's too late.


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## PNWmisty (Aug 19, 2017)

ig0p0g0 said:


> Thanks! Your answer to the first two questions made the third irrelevant, but that was exactly my point - if you are not the one doing the braking, you won't notice that squishy decreased performance feeling until maybe it's too late.


I think your concern is misplaced. Irrelevant.


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## Tophoos (Jul 10, 2018)

I've had the car for less than 2 weeks, and I might be wrong, but I think when it used friction brake, you will feel the brake petal being pressed in, while it won't move while regen braking.

My question is what is the most graceful way to exit auto steer / TACC? Jerking the wheel to exit auto steer makes it look like I'm about to swerve and tapping the brake immediately begins regen brake until I move my foot to the accelerator. What is the proper way to exit these modes?


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## GRiMm-V- (Apr 27, 2018)

Tophoos said:


> I've had the car for less than 2 weeks, and I might be wrong, but I think when it used friction brake, you will feel the brake petal being pressed in, while it won't move while regen braking.
> 
> My question is what is the most graceful way to exit auto steer / TACC? Jerking the wheel to exit auto steer makes it look like I'm about to swerve and tapping the brake immediately begins regen brake until I move my foot to the accelerator. What is the proper way to exit these modes?


You should be able to move the right stalk up to cancel, but it cancels both TACC and Autosteer(no option to cancel only autosteer). Keep your foot on the accel when you do this to prevent regen kicking in immediately.


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## KFORE (May 19, 2018)

Tophoos said:


> I've had the car for less than 2 weeks, and I might be wrong, but I think when it used friction brake, you will feel the brake petal being pressed in, while it won't move while regen braking.
> 
> My question is what is the most graceful way to exit auto steer / TACC? Jerking the wheel to exit auto steer makes it look like I'm about to swerve and tapping the brake immediately begins regen brake until I move my foot to the accelerator. What is the proper way to exit these modes?


Just press UP on the mode selector stalk.


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## PNWmisty (Aug 19, 2017)

KFORE said:


> Just press UP on the mode selector stalk.


True, the Owners Manual makes that clear. It's not even necessary to do a full UP, a 1/2 up will work as well.


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## Tophoos (Jul 10, 2018)

GRiMm-V- said:


> You should be able to move the right stalk up to cancel, but it cancels both TACC and Autosteer(no option to cancel only autosteer). Keep your foot on the accel when you do this to prevent regen kicking in immediately.


Thanks. Come to think of it, I think that's how I would cancel on my old car as well. Don't know why that didn't occur to me. Maybe cause I didn't use CC often. I almost wanted to press the park, but was afraid of what could happen lol.

Anyways, back to OP's question. I confirmed that the brake is definitely pressed down when it gets used, so if you want to get a feel for it, just gently keep your foot on the brake.


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