NHTSA Tracking Braking Loss on Prius Hybrids

I have been reading this Thread with great interest, and there seems to be multiple schools of thought on this subject.

I thought I would offer an interesting aside from a passenger's perspective. Being blind, and having 5 senses reduced to only 4, those 4 remaining senses are (understandibly)more relied on, and I depend more on the input they give me. So, as a result, I am more acutely aware of smells, sounds, touch and tastes, motion is one of those which I am more sensitive to. I often feel ripples or undulations in the road that others don't feel, and VERY slight inclines/declines are easily detected, as well as slight forward or rearward movements.

A few days ago, my wife experienced what is being described here. During a moderate decelleration, she encountered a mildly rough portion of road. After the event, she described what had just transpired, and how it had made her felt. The odd thing, from my perspective, I felt...well...NOTHING!

She reads this forum daily, and is aware of this phenomena with the brakes and uneven surfaces, and I can't help but wonder if this was not an anticipated result.

I'm curious if the feeling of losing braking ability, being it only for a split second, doesn't influence our thinking on what to expect next, which would be (logically)...loss of braking, and an increase in stopping distance, because from a passenger's perspective, it was a perfectly normal, if not run of the mill stop , with NO lurches, jerks or free wheeling of ANY sort.

It is curious that some posters (with multiple K's miles) have never experienced this, and yet others, can produce it on demand.

Is it an anomoly with just certain cars, a general problem with all Prius, driver inexperience, driver inattention, purely a perceived occurance or possibly a total non-event?

Just a little food for thought.

David (aka Blind Guy)

 

Doesn't 2010 Prius beep when TC kicks in? Could some people be associating that warning with loss of brakes and panic?

What if there are no auditable warning at all.... Would the driver percieve as normal. We are getting to the psycology realm.

 

Oh please stop! Those of us who have experienced it KNOW it's real.

 

Ooh, interesting!

I'm going to have to go back to my favorite (and only) bump that triggers this behavior. Could it be that the transition only affects the back-pressure felt on the brake pedal? I've noticed this happen, and the natural tendency is to press harder on the pedal. Yesterday on my favorite bump I tried to keep the pedal in the same position during the transition. This is difficult since the car is bumping and the back-pressure is decreasing. It was doing this as best as I could that led me to the conclusion that the stopping distance wasn't affected. Maybe this whole issue is a snipe hunt?

Thanks for the hint, Blind Guy.

 

We can go back and forth over the entire rainbow of opinion on how people should define this problem or situation. We aren't going to get anywhere. Nobody is going to budge. Those that think it doesn't exist, will believe it doesn't exist. Those that believe it does exist, but isn't a problem, will believe it exists but isn't a problem, and those that believe it's significant enough to be something Toyota should address will believe it's significant enough to be something Toyota should address.

My detached, non-Prius owning, but admiring, opinion is that there seems to be enough evidence to warrant investigation by Toyota. Toyota cannot afford to not investigate this issue.

I also believe High Tech, Hybrid Technology Friction/Regenerative braking aside, braking should be as consistent as possible in any and all automobiles, in any and all braking situations. Please note my use of the term "As Possible".

If this is just a "feeling" that is ocassionally created by The Hybrid braking system then fine, but run tests and make sure that braking distance or function isn't being hampered in comparison to other similar automobiles and yes, a warning that under certain circumstances this "feeling" might manifest should probably exist somewhere in the manual.

One way or another this will resolve. But Toyota as a company can't afford to take the attitude that some owners have taken which is "this is normal, I can live with it". Because as others have pointed out, safe driving distance, even knowledge that it can happen, won't matter the first time someone get's hit and these symptoms manifested during the accident. That's publicity, warranted or not, Toyota can't afford.

So to me the key is reaction on a company level and testing and results. If Toyota can run tests, and I'm sure they can, and say, yes there is a split second feeling that is created in some situations where regenerative braking switches to friction braking BUT it doesn't affect overall stopping distance as compared to similar cars of similar size and weight...then fine. But we need to know. Testing of the brakes under these circumstances should be able to define exactly what is happening and exactly how that may or may not be affecting braking ability.

I also think that as a forum, as a community interested in Prius, we should assume that 99% of us are on the same team as far as wanting what is best for The Prius. Even if we have differing opinions on definition of a problem or best road to resolution.

The quickest way to stop "Trolls" and/or misguided or ill informed national media is for hard test results and reality to be addressed by Toyota. The worst thing for Toyota to do, would be to ignore the issue. The worst thing for us to do as a cyber community is turn on each other over an issue that should be easily defined through testing. Then based on results, the onus is on Toyota to determine whether it is a problem and what should be done about it.

I'm willing to accept either ultimate reality. Prove that this condition can manifest, but with normal braking or just pushing harder...you will stop in a safe distance and in a safe manner as compared to other automobiles on the market, then fine. Warn people that this "feeling" might manifest and move on...

Or, if stopping distance is being affected or the sudden change in braking feel is a real safety issue, then simply fix it.

I'm old enough to remember evolution in braking. Going from Hydraulic, Power, to Disc and ABS....and each evolution had a different "feel". The key was adapting to the new "feel" and the assurance that I was ultimately able to stop with the same affectiveness. Run tests, under these circumstances and prove to me there isn't any loss of ability comparitively and I can accept that there is no issue here.

 

I owned a 2000 vette convertible, it had an awful stability problem. The rear end of the car would skid and flap around like a fish when I stomped on the accelerator. Ironically in 2007 I purchased a new 350Z which did the same exact thing if I did not engage the stability control button. I now have the Prius and no longer have that problem. Thanks Toyota.

 

Besides, not once in these comments have I seen anyone mention the fact that the disc brakes on the car's rear wheels are functioning at all times in their designated way, independently of the front brakes that may be transitioning from regen to friction braking.

It does appear that the transition time intervals on this and its interplay with the ABS system on the GIII needs to be looked at by Toyota.

 

I'm sorry...I just have to laugh. You're comparing a Vette and a 350Z to a Prius then defining it as a "advancement" that The Prius doesn't act like those two automobiles when "stomping" on the accelerator? LOL! Sorry, but you are comparing Oranges to Apples, or Oranges to Cupcakes...(have I missed sarcasm?)

A Vette or a 350Z is designed flap around like a fish if you stomp on the accelerator as the respective vehicles try desperately to take you from 0-60 in some stop watch freezing frenzy.

The Prius is designed to accelerate like you are heading to the drug store to buy adult diapers and a flat of Ensure. The Prius is trying to create momentum with the goal of efficiency and emissions that are clean. Yes, I'm being sarcastic, but rear end spinning acceleration just isn't The Prius's goal as a machine.

Hit the Power button and maybe you won't be flipped off by Bubba as you merge on the highway infront of his 1976 Ford Pick-up but if you ever expected the squeal of tires, burning tread, and a NASCAR Yee! Haw! The the Prius was the wrong choice.

Watch a few episodes of Top Gear, and you'll realize that it's in the design. A Vette and a 350Z are just going to behave in that manner if you "Stomp" on the accelerator.

While acceleration in a Prius IMO is perfectly adequate and even probably more spritely than most people expect, it's design DNA is 180 degrees different than your comparison vehicles.

 

Maybe engineering a mod whereby the rear lights flash when reversing would help with this issue!

 

Yes Sarcasm.
My point being that all vehicles present some form of handling characteristic that may be considered a problem. I remember when ABS was first introduced to the masses and how many folks ran to the dealerships stating "there is something wrong with the brakes" I also did not particularly like the excessive power of the vette and 350Z or even the 1971 Ford Torino with the beefed up 500 cid small block 8. With so many newcomers to hybrid technology, it is no surprise to me that some will have a similar reaction to the tech. Although pressing on the brakes means stopping in any vehicle and/or country, as I posted previously, I did not find that it is a failure of vehicle, design or Toyota, but basically an adjustment of how one drives said vehicle.

 

FWIW, I've driven a Corvette very briefly and found it very easy to break the rear tires loose yes because of what you mentioned later. The car is way more powerful than its tires can handle.

I also have a 350Z but mine has no stability control but does have traction control. I don't have to be nearly as careful w/the Z since it has way less power than the Vette and because I leave TCS on.

The Prius on the other hand is FWD and err, doesn't have much power and then you've got the non-defeatable traction and stability control...

 

Sorry I missed your sarcasm and was taking you too literally. Was a long New Years Night.

 

NO problem, New Year's party still going on here

 

Obviously a very unique and interesting perspective. Another poster somewhat back in the thread suggested the same issue. As we brake we anticipate the deceleration in our bodies and we brace. The input though is from our eyes.

 

I did not notice any surge or change in velocity- so a passenger would not have detected anything was wrong. What I felt was an abrupt loss of brake pedal pressure- as if I had no brakes at all for a second. No instument lights came on.

 

WOW!!... omg, leave this thread alone for a few days and like WOW!

now what is going to happen when after several months, there is no report from the NHTSA? then what we do?

this goes back to what i said on one of the other threads concerning braking. i no longer post on that one after some "engineer" gave me a definition of acceleration and advised me were talking about "jerking".

but i think Blind Guy has pretty much hit it on the head. what we "feel" is the disconnect that happens when we are steadily increases our foot pressure on the brake pedal expecting a steadily increasing braking force and our mind flips out when a sudden reduction in braking force is felt.

i think that part of the reason i have difficulties reproducing the effect (ya, that is ANOTHER thread on the braking issue) is that i am expecting it, trying to reproduce it and therefore when it happens, the effect on the mind is not as great because there is no element of surprise.

now mind you, i have felt the slip when turning and driving over manhole covers, etc. but never thought it was a braking issue. always considered it a traction issue.

 

So, the issue is the pedal pressure? That is totally different from the "OMG the brakes are failing" issue. If it is just the pedal pressure, there is no safety issue whatsoever. Agree?

 

Remember that the original article asked: "Pedestrian lives at risk?"

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No it can be a safety issue if people freak out and do the wrong thing as a result of this perception! I have said all along that I fear someone will encounter this effect and switch pedals instead of continuing to brake. It has only happened to me once and I don't recall any loss of real braking but instead a perceived loss of braking- which can be just as dangerous if someone overreacts!!
It should NOT happen regardless and I hope Toyota finds the problem and remedies it in their current investigation of the matter!

 

Let's pretend this is about steering instead. What if, when you hit a bump in the road, your steering wheel went totally soft as if it did not controll your wheels anymore. Would you consider that a safety issue even if the wheels still tracked properly? I sure would as the effect would put the driver into a state of panic of some sort.