Strange Braking Behavior

[ibis315]

Has anyone felt the Prius accelerate while braking, especially when it hits a dip? I've felt this more than once. Moderate braking and one front wheel hit a small dip in the road. The Prius ICE speeds up and the car seems to accelerate instead of slowing down. Anyone else?

[Sufferin' Prius Envy]

<div class='quotetop'>QUOTE(ibis315 @ Aug 6 2007, 11:28 AM) [snapback]491389[/snapback]</div>

Has anyone felt the Prius accelerate while braking, especially when it hits a dip? I've felt this more than once. Moderate braking and one front wheel hit a small dip in the road. The Prius ICE speeds up and the car seems to accelerate instead of slowing down. Anyone else?[/b]

1) Your Prius is not accelerating under the condition you are describing. It is, however, not decelerating at the same rate for that fraction of a second when the braking system is sensing that bump or dip in the road as a condition in which it needs to correct with the ABS system.

Yes, this has been described many times by many people here on PriusChat. It's not dangerous . . . unless your ICE is actually speeding up . . . which I doubt.

2) What makes you say the "The Prius ICE speeds up"????
It is a very quiet ICE under normal loads and there is no tach. Is this a seat of the pants "feeling" . . . or do you have a Scangage hooked-up to the car?

Don't worry about it. Continue to brake normally. It is one of the funny little idiosyncrasies of the Prius.

[efusco]

It doesn't accelerate, but the degree of deceleration decreases...giving the sensation of that affect.

When braking moderately, if you hit a bump/pot-hole the regen braking will disengage, to get the exact same amount of friction braking the brake pedal needs to be depressed a little more.

You're not gaining speed, you're just not losing speed as quickly as you were before the bump.

[Danny Hamilton]

<div class='quotetop'>QUOTE(ibis315 @ Aug 6 2007, 01:28 PM) [snapback]491389[/snapback]</div>

Has anyone felt the Prius accelerate while braking, especially when it hits a dip? I've felt this more than once. Moderate braking and one front wheel hit a small dip in the road. The Prius ICE speeds up and the car seems to accelerate instead of slowing down. Anyone else?
[/b]

Nah, I haven't felt it accelerate while braking.

I have felt it decelerate less quickly (if you aren't paying close enough attention, this can feel like acceleration) when anti-lock brakes kick in.

[slair]

Gas on the right, brake on the left. Just remember that....

Just kidding, but couldn't resist. :P

[chogan]

<div class='quotetop'>QUOTE(ibis315 @ Aug 6 2007, 02:28 PM) [snapback]491389[/snapback]</div>

Has anyone felt the Prius accelerate while braking, especially when it hits a dip? I've felt this more than once. Moderate braking and one front wheel hit a small dip in the road. The Prius ICE speeds up and the car seems to accelerate instead of slowing down. Anyone else?
[/b]

Same response as those above -- ABS is sensitive, cuts out the braking momentarily when you hit a bump in the road. I find it particularly true when headed downhill, and I've had the same thing happen when (e.g.) pulling onto the gravel shoulder of a road. Definitely scared me the first few times that happened, but 1) I've learned to avoid setting it off and 2) only rarely does it trigger unexpectedly and I now know what it is. I'd never had a car do this before I got a Prius. The good news is that you can both adjust your driving to avoid it and get used to it when it happens. It no longer bothers me (but I remain very cautious when pulling off the road.)

[Sufferin' Prius Envy]

<div class='quotetop'>QUOTE(efusco @ Aug 6 2007, 11:42 AM) [snapback]491400[/snapback]</div>

When braking moderately, if you hit a bump/pot-hole the regen braking will disengage, to get the exact same amount of friction braking the brake pedal needs to be depressed a little more. [/b]

Do Oh, I think you may be correct. If the friction brakes aren't engaged, it wouldn't be the ABS system causing this sensation . . . unless the ABS also cuts-out the regen braking. Something way below my level of Priiknowledge to discern.