NHTSA Tracking Braking Loss on Prius Hybrids

Just remind them that the GM trucks did the same thing. I've owned 3 and driven countless others and many of them produce the same effect when going over good sized bumps.

 

It is scary for any driver when they are braking with light to moderate pressure, run over a big bump or deep pothole, and find the brakes feel like they were released. It is indeed momentary but still disconcerting. I thought it was the Traction Control System trying to get the bouncing wheels back under control. Now I can anticipate the apparent brake loss whenever I hit a bump that will cause one or both wheels to bounce.

 

My wife and I have both had the "brake cutout" issue, her 2009 and my 2010. It is indeed disconcerting and potentially dangerous. I just filed a complaint at NHTSA.gov and hope that they can persuade Toyota to at least address the issue. Ignoring it is not the way to go in my opinion and lessens ones trust in Toyota and their management. Anyone that has ever experienced this issue should file a complaint so that the NHTSA is aware of the amount of vehicles affected.
If no one reports the problem, then there is no problem.

Mike

 

I also experienced this a few times. I am a very experenced driver and pay a lot of attention when I drive. I have to tell you that I was quite scare the first two times when it happened to me. It is almost like losing control and the car accelerate by itself.
Toyota must look into it.

 

I learned this early on in driving: brakes stop the wheels, the tires stop the car. If you have lost contact with the road surface, for whatever reason (with regenerative brakes, friction brakes, ABS active or not), you have lost braking. You are not slowing as you had been. Intuitively, you need to apply more braking pressure to try to stop, and steer to avoid. Before ABS, threshold braking was the answer, and it certainly did not make you stop faster--it just let you avoid a skid so you could steer and maintain control.

(Not to mention the possible effects of the oft-noted fuel economy advice here to pump up the tires to or above max sidewall pressures, versus the 35 psi Toyota recommendation, which further reduces contact patch and can contribute to more severe bounce on rough roads if the owner has elevated the pressures.)

I have not experienced any issue at all in 6 months of driving the Gen 3.

 

Are you sure the Prius Gen III has active pretensioners for seat belts?
This is a feature found only in high-end vehicles, where motorized pretensioners engage in impending crash (based on braking maneuvers or radar) and then release if there is no such event.
You are probably experiencing ELR (emergency locking retractor) that locks the seat belt retractor when the vehicle experiences a deceleration. This is there in all vehicles. Nothing electronic about this.

 

Alokeprasad is correct. If your car is equipped with the PCS (Pre Collision System) then your seat belts will automatically tighten if a impending crash is detected and unavoidable.

There is still the Emergency Locking Retractor in all vehicles not specific to a model or series.

So any car with PCS will have the additional option of automatically tightening the seat belt if the car detects a impending crash.

I believe it's part of the Radar Cruise Control system (DRCC) with PCS on the upgraded models.

 

Auto-Show season is when many of attacks originate.

Look at the subtitle of the article: "Toyota owners are unhappy about the performance of the system, calling it defective. Pedestrian lives at risk?"

Using fear words like "defective" and "risk" combined with the impression of a majority is typical from those wanting to undermine.
.

 

I feel the braking system quite advanced and reliable. It is the best from the huge row of cars I drove in the past. I tested the braking in different conditions (dry tarmac, water, snow, Prague bumpy roads...) and I can say, I was able to control car without any problem. If your wheels are not in contat with the surface their could not brake. It is quite easy, but goverment institutions are sometimes, how to say it, not very clever...
NHTSA looks, from the european point of view, to act as a market preparer and competition adjuster for US manufactured cars .
BTW.33 complains is not too much relative to the number of Ps sold in US.

 

i for one;

*am glad that there is an independent controlled study on the matter being performed

*have not experienced it yet other than the normal slippage that does happen when turning or braking on a manhole cover (we have tons of them and they are slippery even in very dry weather). i even did a detour a few months ago when the noise about this issue was at an apex and was unable to find the right kind of road conditions i guess. we did slip (roundabouts are perfect since nearly all of them around here have manhole covers) here and there, but nothing very exciting. now i chalk part of that up to the fact that it was intentional and expected.

i took my VERY excitable SO with me and told her what i was doing and she claims it to be no more than what she has experienced in any car she has ever driven.

soooo... if a flash is offered to "fix" it and it also addresses the MPG issue, then i am all for it!!

 

The more or less momentary reduction of deceleration on rough
surfaces has been noted in all Prius generations. It is a surprising,
"shocking" to some, fact of life for new drivers. That said, it can be,
and has been for nearly a decade, accounted for in daily driving by
operators consciously revising their expectations of what can happen
when decelerating, and keeping "half an eye" on the road surface
ahead -- admittedly requiring extra effort in bad weather, reduced
visibility, at night, and on unfamiliar roads.

In reading this thread, one question comes repeatedly to mind;
Just how much difference in stopping distance does the matter cause?

It seems like getting the answer would not be simple:
* First, there would be the matter of the road surface irregularity; its
height and its horizontal extent.
* Then, the nature and timing of the driver's response; ride it out or
apply more brake. How much more? How is it measured?
* Finally, the matter of accurate, reproducible measurements may
require continuous measurements of deceleration, as well as
distances.

But, it sure would be helpful to know, whatever the number/s is/are.

As a way of understanding the significance of this matter, I've looked
for similar, if not congruent, conditions that exist in other cases of
switching from a wholly main stream vehicle to something, let's say,
farther from the center, that require a rethinking on the driver's part
of special conditions connected with the new vehicle. I've come up
with:
* Changing from a physically smaller, lighter vehicle to a much larger,
heavier one, or the other way.
* Changing from low to high HP/torque, or visa versa.
* Roll-over and back-over issues associated with SUVs, pick ups, and
to some extents large vans.
* Rear wheel traction issues connected with pick ups.
* Hugely different operational concerns associated with safe operation
of a motorcycle/bike.

Any of these conditions would require a prudent, safety concerned
operator to make changes in the way they drive.

So, beyond its being an unpleasant surprise to new drivers -- it was to
me, but over time I've adjusted -- is the momentarily reduced
deceleration a major safety issue? Is it more significant than the
changes required in the above noted cases?

If so, why?
* Is it that it occurs in a friendly-looking, highly desirable to
some vehicle that on the whole doesn't look like it would have any
little unspoken of issues?
* Is it that mainstream drivers are less forgiving, less flexible than
"early adopters" and let's say, pre-mainstream adopters/switchers?
[Edit:
* A "Let's go get 'em boys!" effort by NHTSA perhaps based in part on
residual suspicion from the recent all weather mat + stuck throttle =
"runaway" investigation.

At any rate, I welcome an impartial, fact finding Investigation, and not
some FUD witch hunt.

FUD; Fear, uncertainty and doubt - Wikipedia ]

 

What problem are you filing a complaint for. Everything I read hear it is happening during light braking. What is being described here is the normal transition from regenerative braking to friction braking. It just so happens that if an obstuction is encountered or "bump" happens, the transitions is more pronounced and includes a momentary loss of braking during the transition. Remember it is during light braking, if you increase the pressure, the braking action will increase and the stopping distance decreased. This is a common place occurance and it would be wise of you to familiarize yourself with it. It is normal. Remember that the Prius is an advanced technology car and has several systems operating to power and stop the vehicle. It will operate differently than a conventional car. In my opinion the momentary loss of braking during LIGHT brake application is not a probem. It is a characterization of the hybrid system and you should farmiliarize yourself with it.

It might be wise to learn how to drive the car and the characteristics of how the car operates.

Also, as I have stated earlier, the traction control operates very aggressively. It works very well, but if you are not familiar with the characteristics you may put yourself in a very bad position. If you are not familiar with the traction control you would be wise to learn how it works now, before you find yourself in harms way because you expect the traction control to operate as your previous cars have.

 

Gen III with PCS have this system. However, even Gen II Prius with VSC and side curtain air bags have pretensioners that activate upon impact. These use explosive charges similar to those used in the air bags.

Tom

 

Rokeby brings up a good point about the difficulty in testing and documenting this. I think someone previously wondered about the FFH, or other hybrids for that matter. I know there are some TCH and HiHy owners on here. Do you experience the same thing? I'm half tempted to try to find a place where this can be reproduced near a Ford dealer and then take a test drive in a FFH and see if it can be reproduced in that vehicle. It would be interesting to see how the Ford engineers have handled this situation.

 

I've read the posts, and while it may have happened - today really scared some brown stuff out of me -- and only at a slow speed...

Turning a corner into a parking lot at maybe 10MPH - the street gutter (nothing special - no holes), I felt a bump, then a thud, with me on the brakes, and the car running towards another car - as the brake pedal went away....... I just kept pushing harder - and it did stop, but woe.... I thought others were a bit paranoid - but that was a very unsettling situation!

 

I've scared some yellow stuff out of a passenger or two with my older Prius.

You drop the pedal to the floor when starting a critical merge or street crossing and they freak when nothing seems to happen. In reality, they were expecting the usual jolt from an engine & transmission and instead the smoooth of the hybrid system.

Unfamiliar feel or different expectations will stir emotion, much like this has.

My favorite complaint is how the Prius was lurching forward on its own. That took us quite a few posts to discover the driver with 30+ years of exerience hadn't ever driven an automatic. He had no idea that was normal. It never dawned on him they would behave differently when you lift your foot off the brake pedal.
.

 

i drive a G3 2010 Prius. i've experienced this braking issue about 5 times now. i don't think it's ABS since there is no *pulsing*. the experience is very similar when you brake on black ice. there's a split-second loss of deceleration which gives an impression of acceleration. it's friggin' scary the first time it happened.

i went to the dealer and reported it. they performed a diagnostic and test drive but they were not able to recreate the problem. so i thought that it was probably just black ice since it's winter here in the Pacific Northwest. but then i saw the Gas 2.0 article about brake failure complaints on the G3 Prius.

see priuschat.com/forums/gen-iii-2010-prius-main-forum/73926-2010-prius-brake-failure-complaints-rising.html

so next time i go to the dealer i'll bring a printout of this thread.

i still love my Prius but i'll keep a close eye on this issue. hopefully there'll be no deadly accident involving this issue. otherwise this could be another disaster for Toyota and a big damage to the Prius brand that we all love.

~C

 

It's bound to happen. Someone will experience this and think they have their foot on the wrong pedal and they will switch pedals and stomp on the accelerator pedal instead...just hope no one is seriously hurt when it happens.

 

Guys, remember to report incidents to the NHTSA (web site or telephone hotline). The more reports they get, the better the chances that they investigate this to the fullest.

 

The ABS on my Gen II Prius doesn't pulse. Older ABS systems pulsed noticeably, but I haven't noticed it on many newer systems. I assume the modulation rate is much higher.

Tom