Braking problem

[2010-V]

Has anyone, with a 2010-V ATP, experienced a forward lunge while driving and braking when navigating over a bumpy road or pot hole in the economy mode? This happens every time I brake while on an uneven surface, not just occasionally. My first thought was that it may be related to the anti lock braking system, however, I am not braking hard when this happens.

This is a very scary experience, fortunately for me this has occurred when there have been no other vehicles, bikes or pedestrians in front of me. The car lunges about two to three feet and regains composure when it hits a smooth or even surface.

Any suggestions or should I schedule a service appointment today?

[mgb4tim]

there's anotehr thread abotu this recently, did you try a search?

[qbee42]

This is caused by a loss of traction during regenerative braking. The issue isn't unique to the Gen III. A quick search of this site will show that the issue is well documented and understood. Whether it is a problem or merely a begin artifact remains a topic of debate.

In short, this is what happens: During regenerative braking, only the front wheels are slowing the car. Hitting a bump causes the front wheels to lose their grip, causing the braking system to stop regeneration and switch to friction brakes.

The car does not lunge forward or accelerate during one of these events. Braking force momentarily drops, which causes a sensation of acceleration. In reality acceleration drops, but sense braking acceleration is in the negative direction, it feels like forward acceleration. The car does not gain speed or jump forward.

Tom

[a priori]

Originally Posted by qbee42

This is caused by a loss of traction during regenerative braking. The issue isn't unique to the Gen III. A quick search of this site will show that the issue is well documented and understood. Whether it is a problem or merely a begin artifact remains a topic of debate.

In short, this is what happens: During regenerative braking, only the front wheels are slowing the car. Hitting a bump causes the front wheels to lose their grip, causing the braking system to stop regeneration and switch to friction brakes.

The car does not lunge forward or accelerate during one of these events. Braking force momentarily drops, which causes a sensation of acceleration. In reality acceleration drops, but sense braking acceleration is in the negative direction, it feels like forward acceleration. The car does not gain speed or jump forward.

Tom

Tom's explanation seems to be the accepted theory, and I have no reason to disagree. I also believe it is benign, though I'll admit it really gave me a scare the first time it happened to me.

It happened on my 2007, and it happens on my 2010 Prius V w/ATP.

The times it is really noticeable are those times when it is scariest: You are coming to a stop or slowing due to traffic congestion, so you know you must avoid something ahead of you; you are braking steadily and fairly heavily, relying on the front brakes (which are using the regen system); you hit a bump, the brake load shifts to the rear brakes (and you do lose, momentarily) the full braking power; the feel is that you are accelerating, despite the fact you are braking; a fraction of a second later the brakes "work" again, and your heart starts pumping normally.

I freely confess that to this day it will put a jolt into me, even though I am fully aware there has been no system failure.

[2010-V]

Originally Posted by mgb4tim

there's anotehr thread abotu this recently, did you try a search?

I did search first and read several posts about braking before I posted this, perhaps I was using the wrong criteria.

[eglmainz]

Originally Posted by 2010-V

I did search first and read several posts about braking before I posted this, perhaps I was using the wrong criteria.

I posted this on another thread myself, as it scared the crap out of me the first time. (Floating feeling when braking)

Ever since, I am expecting this each time I brake, and see the road is uneven, yet it still make me skip a heartbeat each time it happens.

[qbee42]

It gives me a start too, even though I understand it. It's a very unnatural feeling.

Tom

[wvgasguy]

Once on my V and a couple of times on my TCH. Feels like it is freewheeling for an instant but really doesn't cover much ground during this time, just a little unnerving the first time.

[tumbleweed]

Now I know what you guys are talking about. 800 miles on my car and it has happened once, yesterday. Literally had my heart in my throat. I have never felt anything like this in my gen2. I felt like the brakes suddenly went away and I had to push down pretty hard to activate them again, took quite a bit longer to slow down than I expected and I missed my turn. Fortunately no one was ahead of me.

This is definitely not the transition between regen and friction brakes we feel at about 7 mph. This is a very sudden and frightening loss of braking power.

EDIT: If there is another thread on this maybe they should be combined.

[darkleafar]

Originally Posted by tumbleweed

Now I know what you guys are talking about. 800 miles on my car and it has happened once, yesterday. Literally had my heart in my throat. I have never felt anything like this in my gen2. I felt like the brakes suddenly went away and I had to push down pretty hard to activate them again, took quite a bit longer to slow down than I expected and I missed my turn. Fortunately no one was ahead of me.

This is definitely not the transition between regen and friction brakes we feel at about 7 mph. This is a very sudden and frightening loss of braking power.

EDIT: If there is another thread on this maybe they should be combined.

Doug Coleman definetely needs to comment on this.