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Let's say, like a few others, you over-inflate the tires of your hybrid in order to extend FE. That, of course, results in less CSA of the tire that will be in contact with the roadbed at any given time.
It also raises the propensity of the brake pad frictional coefficient being able to overcome the tire's traction co-efficient in conditions that might be marginal to begin with. Keep in mind that the tire does not have to actually lockup/skid/slide in order for the ABS to detect that the rotational rate is slowing so fast it would soon reach lockup provided ABS doesn't intervene.
In most cases with a hybrid the first action of ABS would be to disable the regen system and all the driver would "feel" as a result would be the "effect" of a slight "lurch" forward as the level of braking lessened. It would/might appear/feel as if the ABS did not activate although it did.
All my driving since 1958 has been on cars with fully mechanical brakes, aided by power brake systems after a while and later ABS in several flavors from american, european and japanese manufacturers. Every time, after a while I could expect a certain standard of performance in the brakes, essentially step on the brake pedal and feel the car start to slow. Step harder it slows more quickly, etc. But now I am having to learn a new reality it seems.
Driving my 2006 HH with transmission in D (not at highway speeds for example , take foot off gas, step on brake -- I am expecting but don't sense a nearly immediate breaking reaction and associated slowing of forward movement due to the mechanical effect of brake pads hitting rotors. My car seems to float forward and nearer to the car in front of me who is slowing properly, causing me to press the brake pedal harder to compensate for the delay I initially sense as my pulse races, and invariably making me feel like a fool as everyone in the car jerks forward as I start slowing more quickly than I initially planned. Of course my wife accuses me of braking late. Probably makes life very interesting for whomever is following me ;-')
But you also have to "deal" with FWD, BA (brake assist), EBD (Electronic Brakeforce distribution), VSC (selective unbraking), and ABS that must control/decrease the level of regen braking AND frictional braking.
A lot on one plate.
If the hybrid battery is in need of charging any "light" braking will be biased toward the use of regen "ONLY", no frictional braking involved. So the pedal "feel" will differ accordingly. Since BA will provide more brake power assist with a fast movement from acceleration to braking, or RAPID depression of the brake pedal, there is that to consider also.
EBD will have the effect of increasing the braking toward the rear with the vehicle more heavily loaded, rear seat passengers.
VSC will also "interfere" with braking. If plowing/understearing is detected VSC will actually release front brake pressure slightly while increasing rear brake pressure. Overstearing during braking, while not as likely with FWD or F/awd, will result in "unbraking" of the front wheel on the inside of the "skid".
Strange new world.
In our 06 HH, we easily ignore the "slip" sensation by applying firm and continuous pressure on the brake pedal, this method stops the car just fine and within expected distance.
The first few times that this slip happened way back in 2005, I was caught by surprise and hesitated on the brake pedal. That caused my stopping distance to lengthen. We did that twice and have since adapted.
Our 06 HH does not require a bump or even a patch of loose dirt/material to experience the slip. It normally happens within the first 2 miles and then not again. Even then, it does not happen all the time within the first 2 miles. We experienced this slip a few times this past Winter and it has not happened since.
We do not perceive a "slide", more of a "slip". It is as though the brakes begin to work and suddenly let go for a moment before catching again. A slide is the car locking its tires and sliding.
Toyota should see about fixing this with a better solution but for those of us who own this car, the workaround is to expect the slip and learn to ignore and apply continuous and firm pressure on the brake pedal as in any other car.
This past winter....
In my experience a very light layer of oxidation/rust will often form on the wet rotor surfaces overnight. That would tend to make initial frictional braking efforts early in the next drive a bit more effective.
Unlike earlier versions of ABS the newer models PREDICT that wheel skid/lockup is imminent, the rate of rotation of a given wheel is declining so rapidly a skid or slip is predictable unless some corrective measure is made. Therefore with a hybrid there can easily be times that an initial activation of ABS, an initial activation that ONLY disables the regen and that alone alleviates the problem, might be what you are describing.
And remember, unlike ABS that can selectively UNBRAKE any ONE wheel, or wheels, that exhibit impending lockup, disabling regen affects the braking level of ALL driven wheels. So ABS initial disabling of regen to prevent impending lockup will have a fairly dramatic effect on the rate the vehicle is slowing and other than watching the energy flow display there may never be an indication to the driver of just what has transpired
Now, KNOWING the "wheel" in question is operating within the "cusp" between rotating and not, the transition from combined regen and friction braking, or even worse, from ONLY regen braking to frictional is NOT a simple task for the engineers programming the ABS/VSC/TC/EBD/BA firmware to manage.
I wonder if the use of the brake "arming" technique using the windshield wiper rain detector in use by some upscale vehicles might be of help here. Even if only regen braking is being used apply just enough brake fluid pressure to the caliper pistons to bring the brake pads into "firm" contact with the rotors.
During this past week, I have noticed a new problem. Sometimes the regen fails to kick in when it should. The coasting regen works fine, but when braking for a stop at the bottom of a downgrade, sometimes the braking regen system does not kick in. Sometimes the battery is fully charged, sometimes only about half charged, so charge level is not a factor.
Road conditions are not a factor. I drive 3 miles (minimum) on gravel roads when leaving home, or returning, and the braking regen functions normally on gravel (until recently).
Someone mentioned tire pressure. They should be all OK, but I will check them and see if that makes a difference. (According to the tire pressure monitors, they are all nearly identical in pressure, but I am not confident their accuracy is exact.)
I am reluctant to bring it into the dealer until the failures are at least 50% of the time, or he might have my car for a few weeks.
Anybody notice this problem? Anybody have any advice?
But, here is the punch line. I called the Lexus service dept. and they played dumb. That is, they pretended to have difficulty understanding me. They never heard of a problem like this, etc. I am afraid to bring it in because they sound incompetent.
My Highlander regen problem does not appear to have anything to do with rough roads. It happens as often on pavement as it does on gravel farm roads (and some of them are very bumpy) but I will keep an eye on the "rotating wheel" display and see if it shows any relationship. Good suggestion. Some of the roads I drive on have bumps, and I will try to keep track of bumps and see if it is bump related.
Alternately, polar to this, 5 minutes from home coasting on a bumpy road slightly up hill to a stop sign, the regen stayed on after stopping. When I continued the engine moaned and labored, so I let up on the gas and coasted but it moaned when I depressed the gas pedal again. Next time I will touch the brakes to see if it resets the regen. It's the opposite of what is happening when the regen discontinues while braking.
We are experiencing the braking gap at moderate to low speeds, in rush-hour stop and start traffic (go 50 mph, then slow way down, repeatedly), on smooth roads. It feels as if the brakes are working, then suddenly stop working, and then resume working. The period during which the brakes are not working feels almost as if I am fighting against acceleration. Having rarely driven the HH since we bought it, I have been driving it daily since August 2009, as my commute requires it now. I was bothered by the braking gap experience, before the stories of runaway Toyota/Lexus cars came to our attention. The braking gap alone was worrisome because a) more distance seemed to be required to stop, which could lead to an accident, and b) it seemed as if the accelerator was involved, which would lead to lower fuel efficiency. But when the run-away Toyota/Lexus story broke, the CNN coverage of highly educated, extremely concerned, credible people talking about their run-away cars, with no floormats near the gas pedals, and an expert with a chart showing rapid increase in run-away cars after a computer governing the throttle was introduced, I took notice. Toyota seems to be doing no better than Ford did with their Explorers when the Firestone tires were killing people, and I had become more concerned about the braking gap problem. So I am quite relieved to see that others' accidents related to the braking gap problem have been relatively minor, although still hair-raising, compared to the other Toyota/Lexus scenario, with the crash-and-burn outcomes.
I gather that I need to adjust my driving style. No longer can I count on the consistent braking I have long enjoyed as a driver of German and Swedish cars. I will have to anticipate the braking gap, and try not to be bothered by what feels like equipment failure, until I can replace the 2007 HH.
We have spent over $100,000 with Toyota Lexus in the last five years, buying a Lexus for each of two college grads, and the HH for ourselves. We gave Toyota/Lexus the benefit of the doubt on safety, and allowed them a spot on our short list of Trusted Brands in the car category. They have now removed themselves from the list. We were down to one Lexus, and the HH. The Lexus was traded in for a German car last week. Now we're down to one slightly problematic (we hope) Toyota Highlander Hybrid with a braking gap. Thank you for your help in calibrating this risk.
With a hybrid the FIRST action of ABS will be to DISABLE regen braking. Disabling regen ALONE may resolve the problem. The result is that ABS activated without your EVER being aware. All you thought you felt was a surge or lurch forward when regen ceased opperation thereby (momentarily) lessening the braking HP.
Also. There are MANY instances wherein a single pulse of ABS would be all that was needed, would be "felt" by the driver via the brake pedal kick-back or otherwise. With a regen vehicle all you "feel", think you feel, in these instances is the slight surge or lurch forward.
Since NON-ABS controlled/limited braking is deemed so highly dangerous there are indications that regen braking is disabled/reduced/limited somehow in cold sub-35F temperatures. Even moreso for most hybrids since there are consistently FWD or F/awd. Ford, I believe, disables regen entirely during coastdown periods if the temperature is sub-freezing. Obviously regen MUST be disabled anytime ABS (initially) activates.
The first incident happened in a parking lot in early October ’09. The Lexus would not stop and ran over the curb and walkway and ended into a grassy area near a fountain. We ignored this incident and did not report it until the last incident happened. The last incident happened at a one-way stop which crosses the intersection of a two way heavily traveled thoroughfare. The car failed to stop at the stop sign, crossed two lanes of traffic, and ran into hedges and a street sign before coming to a stop. There was damage to the body of the car (bottom & front). We reported this to our Lexus Dealer. They were very nice to accommodate us with a loaner car. They sent our complaint to the Lexus Customer Satisfaction Center in Naperville, IL. Their complaint investigation was totally unacceptable. They advised that they have no history for the subject warranty problem and repair records and are unable to duplicate our concerns.
We are surprised that Toyota/Lexus did not even consider human life issue or even their own brand image. They should know that similar problems did occur and exist in Prius and Highlander hybrid vehicles during the past few years and are all shown on this website. I can’t believe that Toyota/Lexus ignore this problem and don’t even educate the vehicle operators on how to control the brake if this is a minor problem (which I believe is a major problem).
I don’t want to wait until someone crashes and dies.
Please advise me what action I should take or how to advise the other owners so they won’t be sacrificed.
So far, most HH owners have reported a "slip" or "gap" in braking at low temperature but few, if any, have reported incidents that resulted in a "run away" condition as you have reported. So I will caution against generalizing this to be something that has been reported "all over" the web.
I have heard of ABS incorrectly activating at very low speed (Chevy?) when it ought to shut off. ABS activation at low speed causes the brakes to not fully engage so the car keeps on rolling. Low speed rolling though should not send a car across so many lanes plowing onto curbs. So something is definitely wrong with your vehicle.
Unfortunately, the recent "gas pedal" run-away problem that resulted in deaths have shown that Toyota will also hide the truth and refuse to acknowledge safety concerns. It continues to blame the matt instead of looking into the accelerator system. Anyway, do be careful how you make the claim.
All that said, I am losing confidence in Toyota's reputation. Having a defect is one thing but refusal to own up to the problem and fix it is much worse. Time to look at Ford again.
By not grabbing, do you mean the brakes did not work? Or did you cause the car to lock up and skid because ABS did not work?
The manual states that ABS will not activate under 25-MPH. This is not new and is actually a requirement of ABS systems. ABS is supposed to shut off at low speed else it will keep the brakes pumping and not able to stop your car. This is a totally different problem that the ones we have been reporting? Is this what you are experiencing?
This could be a loose connection. The dealer says he never of heard of this problem. But, it could also be a bug in the ABS or stability control systems.. That is, the small bump could stop wheel rotation which is sensed by both of these systems.
Thanks for trying to help...
Wonder when HH's will finally be recalled to address the braking gap problem.
Statement Regarding 2010 Model Year Toyota Prius Inconsistent Brake Feeling
In certain 2010 model year Prius vehicles, Toyota has received reports that some customers have experienced inconsistent brake feel when the vehicle is driven over potholes, bumps or slippery road surfaces.
Toyota is currently in the process of confirming these reports and investigating the vehicle driving conditions under which the reported phenomenon occurs. It would be premature to comment until the investigation has been completed.
Today Toyota released info. that they had fixed a problem in Prius where the gap in braking was noticeable. They did not do a recall, but said it was a programming problem they corrected in models designed after January. It's disapointing that it wasn't made public before now, but I would guess that many companies do this.
We just sold a Mazda CX9 with multiple problems, none of them recalled or discussed by the company, even though service knew them to be recurring problems. We bought a 10 HiHy fully loaded except DVD at invoice plus $200 for color (only amethyst pearl equipped this way in California) but discounted XM install $400, so all good. We feel very confident with Toyota and were happy to get the discount, as he had been quoted $1500 and $700 xm install over invoice at the beginning of the month. Good luck with brakes, ours seem ok but will take to the dealer if a problem comes up.
I will give an update on Tuesday. In the meantime, everyone who owns a Toyota/Lexus hybrid, start your complaint. There is a safety problem with these cars. It is the best way to save us all money and maybe a life.
P.S. If your gas pedal sticks, PUT IT IN NEUTRAL!
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You are absolutely right, and beat me to the punch. I just filed my complaint on the NHTSA web site myself. If everyone with this problem files a complaint, maybe Toyota will include our HH's in the recall effort (as they should).
It definitely is NOT a loose connection. Your description is the best and clearest I have read since 2006 because you included the charging-meter behavior.
Our '06 HH behaves exactly the same as you described *except*, the braking "slip" happens even when it is not hitting bumps. It happens when weather is cold. Once the car has been traveling for a few miles and everything "heats" up, the slippage never happens again.
I hope Toyota simple would acknowledge there is this "gap" and just fix up for all of us. We have been dealing with it since the 206 HH model year! Enough is already enough!
I am relieved to learn that I am not the only one with this problem. One would think that I was if one talked to the Lexus dealer!
I will start looking for changes in braking behavior as the car warms up. I bet I will see the same thing you are seeing. I will let you know..
Fwiw, my take on this has always been that its not an electronics 'problem' per se, but a more simple fact that the logic can't always predict the exact amount of friction/stopping power that your brake pads will provide at any given moment -- so when the regen kicks off, if the pads are particularly wet/hot/cold or whatever, and say you were near the limits of the regen's stopping power -- the transition to pads may be more or less noticable due to the change in stopping power provided.
Go to: http://www-odi.nhtsa.dot.gov/ivoq/index.cfm
Or call: (888) 327-4236 Expect to be on hold for a few minutes. I put my phone on speaker and went about my business until they picked up.
Highlander Hybrid Drivers should not have to put up with brakes that slip,ever.
Personally I am currently a champion of using ONLY the rear brakes initially, for light to moderate braking, and then only transitioning to the inclusion of front braking if a preset brake fluid pressure threshold is reached or ABS detects impending lockup.
My '01 F/awd RX300 gives me that same "lurch" feeling as I slowly brake to a stop below 10MPH and the transaxle upshifts in order to alleviate the potential danger of loss of directional control arising from engine compression braking should the roadbed be slippery.
Noticed it back at the beginning but it faded into the background.
And yes, there would most definitely be a transitional feel, in this case MORE braking coming online, but to the overall benefit of additional safety. Also make more use of those rear brake pads.
I have reported this to the NHTSA and unfortunately, even though many people seem to be complaining about this problem for High Hybrids only seven have filed a complaint(I asked the woman who took my complaint). Now maybe she meant for my particular year and model the High HYb Ltd 09, but she still said they haven't gotten enough complaints for them to recommend a recall yet.
If you want to file a complaint go to this site:
http://www-odi.nhtsa.dot.gov/ivoq/index.cfm
I find that it occurs at about 25-30 mph speed and I have observed it during colder days. No, it is not ice or wet roads, it is an inherent braking problem in the car that Toyota dealers and Toyota continue to deny or plead innocence.
I suggest that you file a compalint with NHTSA at
https://www-odi.nhtsa.dot.gov/ivoq/Complaint.cfm
Make sure you use Hilander Hybrid in the vehicle selection. If we all register our complaints, hopefully NHTSA will be able to get Toyota address the brake problem with Hilander Hybrid too.
To be clear, the "skip", "lurch" or "slip" has not in anyway shortened or threatened our stopping distance. After the first few instances during Winter of 2005 (bought ours in July 2005), wife and I learned to just be decisive, keep up the pressure and ignore the "lurch". We have stopped on ice, snow, slush, sand (Death Valley), road, dirt trails, rain and ranch/farm mud and muck without problems since we have owned this car.
We have driven through the Sierras at various speeds and in various conditions from summer heat to winter snowfall with 6 or more inches on the ground. We have towed all the way through the Shasta range on HWY5 all the way from Redding into OR.
We have also towed Brenderup horse trailer and utility bed trailer onto slick grasses and dirt roads without stopping problems.
While we all dislike this "lurch", it is most likely not the same problem as the current brake-failure fiasco. Like WWest, I do not believe this is brake disengaging or not catching. I believe braking is continuing but it is the switch from regen to mechanical that is causing this "sensation". If anything, our "stopping problems" have all been related to lousy tires.
Anyway, if Toyota would use software or some other means to fix this, I would really appreciate it. It certainly would boost my confidence in Toyota a bit. As it is, Toyota's long drawn-out denial after the CHP officer crash has really soured my trust in the company. Especially given we have many friends in CA law enforcement. For our next purchase, I will be looking at alternatives. Ford is a good choice now if it offers any solid and reliable larger hybrids. We will keep our HH until it dies.
If you think about it, Toyota could install accelerometers in some test vehicles, sample data from the brake, regen and the computer systems and analyze the data to evaluate the problem.
Since several of us are complaining about brake problems in HH, this should not be such an elusive problem as some reports have suggested.
And while you're there why not file a complaint about the ICE shutting down unexpectedly in certain situations. Hey, you bought a hybrid, now learn and understand, and live with, its idiosynchronies.
I have little doubt that many owners felt this same way when they first encountered ABS activation...hey, something is wrong with my car, its acting funny when I go to stop.
All of the above fits..."does so unpredictably".
In every other car I've owned with ABS and VSC (haven't had the other acronyms on prior cars), these features would kick in only very infrequently.
On my HH, at least, the braking gap happens on a daily basis, but not consistently.
With a FWD hybrid is it possible that the "gain" of the Anti-lock Braking System is increased as the climate grows colder..? ABS reacting much quicker to "impending wheel lockup" if the OAT is hovering near or around freezing...?
An ounce of prevention is better than a pound of cure...??
Regen braking applies ONLY to the front wheels, so if the rotation rate of those front wheels starts declining too far outside the "envelope", predictive target, ABS might disable regen as a pre-emptive measure.
That certainly would account for your feeling that these events are more frequent with the HH vs non-hybirds.