Toyota Prius Brake Problems



  • stevieg3stevieg3 Member Posts: 1
    I had my first experience with my Prius sliding on wet roads today. I have an 06 Prius with 65,000 miles. I was driving all day in the rain. Car was going about 25 mph on a curve with brakes slightly engaged. The Prius did a complete 360 degree turn as I watched in amazement and fear. The ABS never engaged. By incredible luck, there was no one else in the road at the time (2:00 p.m.) My gas tank was nearly empty (I noticed someone mentioned this in earlier post.) After the 360, the car drove normally. It is a strange coincidence that this occured in the timeframe when all of the publicity about '10 Prius brakes and other Toyota problems has come out. Up until now, I was a strong Prius advocate, sometimes wondering if I should get a paycheck for adverstisement. The advocacy stops now. All advice would be appreciated.
  • jskr1977jskr1977 Member Posts: 2
    I just found this forum. I thought I was insane. I've had two episodes on ice where I've hit the brakes and nothing has happened while driving my prius. No anti-lock kick in, no staility control kick in, no sliding to indicate that I was swerving and no change in speed at all. I was driving at a low speed (about 12 miles an hour) and was very lucky to be alone at the time. I've driven my 2007 for almost three years now. I'm very comfortable with how the breaks feel, I didn't fell any change in pressure when I hit the brake at all. My minnesota driving skills kicked in and I tapped the brake several times and eventually they kicked in again. It worked both times. I know you aren't supposed to do this with anti-lock brakes but it's better than having an accident!!!
  • sleshslesh Member Posts: 1
    There is definetly a brake problem with the 2010 Prius.I have one that is 3 months old.I like the car a lot but the brake problem is there.When brakes are applied and the car goes over a bump,man hole cover or railroad tie the brakes disengage and the car continues on forward.I had a Chevy Suberban with the same problem and after almost hitting the 3rd car,took it back and turned it in.I would never let my wife drive that car either.There will be a recall I am sure.
  • gcallawaygcallaway Member Posts: 1
    We purchased a 2006 Prius and on multiple occasions, my wife infomed me of a braking problem. When she would come to a stop, the brakes would not work…and she would end up in the middle of the intersection. This started happening once a month. I would test drive the vehicle, and nothing would happen, for me. Until one day I was driving with the wife and two small children in the car. I was approaching an intersection and the brakes would not work. I ended up rear-ending a truck who was parked at the intersection, causing apprx. $1,500 in damages to our Prius. Luckily, the truck stopped me from getting T-Boned in the intersection.
    I immediately drove the car straight to the Toyota dealarship in North Arlington, TX and left it there. They ended up driving it for minutes and could not get the brakes to fail. I had informed them that they would need to drive it for a month (since it happened once per month). They ended up sending me packing, with a $1,000 rental car bill as well as a damaged Prius that they claimed no responsibility for.
    Somebody needs to check how many people have perished from driving into intersections because their brakes have failed.
    I almost lost my wife and kids on multiple occasions, because of their faulty brakes.
    And yes, I immediately traded the car in on a new car that was not a Toyota.
  • alan94alan94 Member Posts: 1
    OK, this is weird, because I had the SAME EXACT problem with a 2005 Camry. I brought it to the dealer twice, and they insisted that the brakes "conformed to standards," and was never able to get any satisfaction. Amazed to hear these latest complaints.
  • edtsuiedtsui Member Posts: 1
    I have also experienced on quite a number of occasions that when I tried to brake the car surged forward. I brought the car into the Toyota dealer and they said they could not replicate the problem and they said they have never heard of the problem. They were obviously lying. I am glad that the problem is being looked into now. I have a feeling that Toyota is aware of the problem, but is trying to stonewall. Terrible experience and I will have serious reservation of buying another Toyota.
  • techie2003techie2003 Member Posts: 2
    Like many others on here I thought that I was crazy. At least a dozen or more times I have tried to apply the brakes while driving on a rough surface with absolutely no brakes. Several times it has occured when approaching an intersection and there are indentations on the road that maybe trucks or heavy traffic have made. There is no indication of the ABS being applied and the pedal is still firm but the brakes just don't work. Once you are past the rough areas the brakes kick in.
  • ssagessage Member Posts: 1
    I've had 3 occurances of my brakes reacting excessively to the point of being scary. The brakes are designed to automatically increase when you step hard on the pedal, but I have been in traffic situations where I needed to just tap the brakes after merging into highway traffic. Instead of a tap result, the automatic function has taken over and slamed the brakes hard. This has created a serious risk of having the car behind slam into my rear. So far I have not had an accident and I have learned to be REALLY careful about touching the brakes, but I have no doubt there is something wrong. I have an appointment with the dealer to have it checked.
  • chucko3chucko3 Member Posts: 793
    Believe or not. It happened to my Lexus 07 GS350 AWD as well.
    One time to my wife last year when the road was covered with 3 inches of wet snow.
    Going home from work she told me every time when she tried to brake and make the right turn, the car wouldn't slow down and she missed the turn. She missed a couple
    turns. Luckily there wasn't any body on a snowy road.
    And I thought her driving skill in the winter wasn't that good. She does not drive in
    snow storm often.

    Happened to me twice this winter and I thought the tires don't have enough tread depth.
    On each occasion, the road was covered with 1/2 inch wet snow and on a slight slope.
    The car just wouldn't stop when I applied the brakes.
    I posted this problem on Lexus GS350 board more than ago,
  • avucarguyavucarguy Member Posts: 56
    I cannot speak for those with 2010 Prius. My 07 Prius has 62K on the odometer now, and no brake failure. I do notice the weird movement(slips?) when I brake going over a pothole, but only momentarily about a second or less. The stability control light lighted up for about a second while this is happening. I take this as a normal function of the car and nothing more. This has never caused I or my wife to get into any accident. Let's not get paranoid and blame Toyota for everything that happens. I know for a fact that Toyota/Honda/Subaru/Nissan/Mazda cars that I have owned have been very reliable, especially Toyota and Honda. I would take these cars over the 4 POS American cars I have owned in the past.
    Sometimes accidents happens due to circumstances beyond our control, poor driver skills or judgment. Those of you that are truly unhappy about your Toyota, trade it in for a GM or Ford. Both these companies are offering $1000 extra rebate for a Toyota trade.
  • tigergarytigergary Member Posts: 1
    Those who have experienced unexplained braking problems should file a complaint with the National Highway Transportation Safety Administration (NHTSA). If they receive enough complaints they will do something. And from reading this forum, it seems there are a lot of scary failures.
    I have 45,000 miles on a 2005 Prius, with no braking problems until this last month when twice my lady has reported to me that the brakes grabbed hard when she pressed the brake pedal lightly. Someone else reported a similar thing in this forum.
  • brendabeibrendabei Member Posts: 6
    Now we know why

    Toyota says Prius had brake design problems
    Toyota says Prius had brake design problems, already fixed on some models but not on others

    that was in the news today
  • doobs1doobs1 Member Posts: 1
    SO, according to the news, Toyota fixed the brake problem in some 2010 Prius cars as of late January.
    I am supposed to get delivery on my newly purchased Prius this Friday.
    How do I know which cars were fixed?
    I dont want to relay only on the salesman knowledge.
  • ddemarcoddemarco Member Posts: 1
    I have 110,000 miles on a 2005 Prius, with braking problems which I attempted to report within a month or two after my purchase but was led to believe there was no problem they could find. Today, I just avoid braking over bumps or pot holes because of the surging it creates. At least now I know I am not losing my mind. Don't get me wrong I love my Prius and will get another real soon however, Toyota should fix these issues for all that are having troubles. I will be waiting for that re-call letter in the mean time. Happy motoring Dennis
  • garzzogarzzo Member Posts: 1
    I was very interested in Juro Osawa’s article in the WSJ yesterday on Prius brake failure. I am an American in New York State who recently (November 13th, 2009) had an accident in my 2009 Prius that totaled the car, though no one was hurt. I had always credited this crash to a problem with my brakes. I was in a situation where I had to stop very quickly and braked as hard as I could. The car slowed to a point than seemed to plateau until my car just cruised right into a truck. I never heard or felt the “ABS sound” or vibration, and had always suspected something was not right with the brakes, but did not know what I could do about it. How interesting now to hear now of Prius brake failures; I can attest to the fact that it is not confined to 2010 models.
  • liliyaliliya Member Posts: 2
    Thank you for your post. I have 2005 Prius with 73,000 miles on it. I know now that I am not unique and do not do anything wrong. A week ago while approaching a busy intersection, I pressed my breaks, but the car hit a bump, speeded up, and I ended up almost in the middle of the intersection. Luckily, nobody got hurt. The jump like this was not the first one, but this one was very scary. I am going to my dealer, but I do not think they can do much. You cannot really avoid bumps on the road, and we never know when we need to push the breaks. Other than that, I am happy with it, but I will not recommened it to my children.
  • steveindenversteveindenver Member Posts: 1
    I filed my complaint today with the National Highway Transportation Safety Administration (NHTSA) through their website. I first noticed the issue when approaching a traffic light that had turned red. I was braking as I hit a small unavoidable pothole, and to my surprise, my car lurched forward nearly hitting the car in front of me. For almost two month I have had to routinely drive that road, and consistently when I am braking as I hit the pothole, the brakes give out for a brief second. I now give myself a rediculous amount of space to stop whenever I approach this intersection - that has saved me from getting into a wreck - but I am now familiar with that intersection/pothole scenario. It's far too easy to get into an upredictable stop scenario. Hit a bump - and you might not be able to stop in time - leading to a possible brake related fatality.

    I called my dealership today - they offered me a rental car while they wait for a fix from Toyota. I am nervous about that - they have no concrete word from Toyota as to when the fix will be released.

    Please! For your own safety, if you have a Prius (especially 2010), do the following test:

    1. Find a street or parking lot with a small pothole or uneven pavement (doesnt have to be huge - just enough to cause a good bump as you drive over it) where you can safely test the brakes.

    2. Drive over the pothole at about 20mph - making sure brakes are applied before you drive over the bump

    3.) As soon as you hit the bump, you will feel your car 'lurch' as the brakes shut off.

    4.) If your car exhibits this behavior - file a report as soon as possible with NHTSA.
  • wwestwwest Member Posts: 10,706
    Unless you need to make stearing corrections ABS is ALWAYS detrimental. IMMHO ABS should NEVER activate unless VSC indicates a need.
  • Sunny369Sunny369 Member Posts: 11
    Thank you for all the information. I definitely will do the test as you said. And Toyota just announced recall for Prius. Now I am wondering what I should do with my car and the resale value of the car. :sick:
  • keizaikeizai Member Posts: 1
    I just found this forum, too. I thought I was alone.

    On the morning of June 9, 2009 I was traveling South on I-93 near the town of Medford, MA. I was on my way to Logan Airport to return the 2009 Toyota Prius I had rented that previous Wednesday. It was approximately 9:30 AM; the freeway was still bumper-to-bumper with rush hour traffic. I was in the left-hand lane of the highway and traffic was stop and go.

    A gap opened up in traffic and I accelerated. The car in front of me (approximately 60’ ahead) suddenly stopped. I slammed on the brakes but my car kept going. There was nothing I could do as my car plowed into the car in front of me, at the speed of approximately 10 mph. The impact was sufficient to dislodge my license plate. There was no apparent damage to the car in front of me, however the two passengers were extremely shaken up.

    There was a Massachusetts state trooper on the scene who took all the information but did not file a report. As soon as I could, at about 11:00 AM, I called my insurance company, USAA to report the accident, and I explained all of the details to them.

    It is unfortunate that these problems are just now getting attention. Think about how many accidents could have been avoided if this issue had been brought to light sooner.
  • wwestwwest Member Posts: 10,706
    In some sense what you are describing is SOP, Standard Operating Procedure.

    With these hybrids when you apply the brakes the system is biased toward the use of regen braking, more HEAVILY biased the lower the hybrid battery charge level happens to be.

    So, you're braking moderately, using regen braking only, in order to come to a reasonably gentle stop. Then for whatever reason (pothole, railway rail, plastic crosswalk stripping, wet/oil spot, etc) ABS detects impending wheel lockup and instantly DISABLES regen braking in favor of frictional braking only.

    Note: In many cases you may never know ABS has "activated".

    Now, for a brief moment you might feel a "surge" forward due to the transition period between the time of disabling the regen braking and the frictional brake pads coming into contact with the brake rotors hard enough to reach the same level of braking you had just previously.

    Even worse if the street is oil and rain slicked ABS will kick and you you might well feel that as brakes grabbing. It is not at all unusual for ABS activation to result in elongating your braking distance in a fairly slippery surface by an extraordinary measure.
  • buyamerican2buyamerican2 Member Posts: 16
    So, if I am understanding you correctly, you are saying that if you want to be able to stop reliably on uneven or somewhat slippery surfaces, you better drive something other than a Prius.

    Since I do not drive a Prius, I will from now on turn on my hazards when it is raining and there is a Prius behind me.
  • ericqliericqli Member Posts: 3
    I have a 2006 Prius. I noticed the issue of the car surging forward momentarily when a pothole or a bump is hit (and the VSA light comes on). Like many others, I thought this was normal and just ignored it. But apparently now Toyota has recognized this as a problem, but only for the 2010 model. I went ahead and filed a complaint on NHTSA's website. I urge others to do the same, so we can get our non-2010 models fixed as well.

    Another problem I noticed is that when the road is wet, and if I was at a complete stop and tried to accelerate too fast, the car will actually kind of "slip"--it doesn't accelerate as intended but actually stalls momentarily. The way to overcome this problem is to step on the gas pedal very lightly. So with slow acceleration, everything is fine, but if you tried to rush it, it won't work. This is a severe disadvantage if you are sitting at a busy intersection trying to make a turn, because you want to go fast to avoid be hit, but like I said, trying to go faster will actually backfire.

    Has anyone else noticed this?
  • dturrdturr Member Posts: 70
    The main Toyota brake pedal problem is mechanical and that I can understand.

    However it is a whole new ballgame when computers start playing up.
    I just think of this thing in front of me and the problems I have, with a need to power cycle the thing every month or so. You cannot do that travelling at 70mph.

    Better the old days when brakes were a mechanical function you always seemed to have warning when things were not right.
  • molo1033molo1033 Member Posts: 1
    I have had the same problem in my 2008 Prius. I just figured it was how the Prius worked, I didn't realize it was a problem. But I will definitely be filing a complaint now.
  • wwestwwest Member Posts: 10,706
    "..Has anyone noticed this?.."

    SOP, again.

    That's called TC, Traction Control. If you try to use too much engine torque for roadbed conditions the drive, driven, wheels will tend to slip. When that happens TC will activate and instantly reduce the drive power from the HSD system. Most of the time it will also apply braking to the slipping wheels.

    With a FWD or F/awd vehicle wheelslip/spin of the drive/driven wheels is of such seriously hazardous nature, HIGH potential for subsequent loss of directional control, that the TC reaction to the must be INSTANT, full and complete.

    If you happen to also be turning as you accelerate the TC (more likely VSC)functionality will likely be even more firm and sudden.

    Keep in mind that for its weight the Prius has an unusual level of get up and go from a full stop. Low speed torque derived from those synchronous AC motors.
  • wwestwwest Member Posts: 10,706
    " better drive something other than a Prius.."

    No, not saying that at all.

    What I am saying is that if you drive any of the current crop of hybrids that use regen braking you should be prepared for that seat of the pants "feel" of a momentary, millisecond, forward surge. In most cases that momentary "lurch" in brake application will have no detrimental effect.
  • london6london6 Member Posts: 1
    I'm in exactly the same boat....supposed to pick up mine Friday....if you get any tips, please let me know....I'm in about you?
  • tryingedmunds2tryingedmunds2 Member Posts: 8
    Nice explanation to the Prius braking characteristics.

    We have a 2010 Tacoma 2.7L Auto and after 16,000km (10,000miles) I am bothered by its braking performance and wonder if there are some common software/hardware related deficiencies in Toyota's products, I have two questions.

    1. This is our first ABS vehicle and it does seem to be harder to stop with ABS than our old Civic with non-ABS brakes on snowy or icey surfaces. Are there any quantitative results for ABS vs non-ABS performance?

    2. The Tacoma also exhibits unexpected brake-force requirements. Usually requiring more force than I think is warranted but occasionally responding to my idea of normal braking pressure. Is this appearing on the Prius as well as other models in Toyota's line-up?

  • wwestwwest Member Posts: 10,706
    1.) There are most definitely times, situations, wherein ABS is a detriment. ABS will ALWAYS extend your stopping distance in panic, severe, braking situation, in favor of allowing the driver to maintain directional. Sometimes that simply is not the optimal thing to do. I have contended for quite some time now that unless the stability control, VSC for Toyota, indicates directional control or directional correction is needed then ABS should be held inactive.

    On a highly slippery surface it will sometimes help to apply the e-brake slightly/judiciously along with normal braking. I have had times when it seemed my Jeep would never come to a final, full, stop due to continuous ABS activity. The e-brake would always help.

    2.) "..unexpected brake-force.."

    That may be due to BA, Brake Assist, if you happen to have that feature. With BA the braking system "watches" the rate at which you depress the brake pedal in order to determine if "this" is a panic or severe braking event. If it determines so then it will actually use the ABS pumpmotor brake fluid pressure to assist your braking effort. In that case it might even extend the HARD braking period should you relax brake pedal pressure somewhat.

    As a result "normal" braking will often require more brake pedal force vs if the system detects panic braking and provides the extra assist.
  • techie2003techie2003 Member Posts: 2
    I mentioned earlier about my 2008 brakes not working properly when you hit a rough surface but I did not mention the other problem that you have. I have also had a problem with acceleration if you are on just a small amount of cinders (spread in the winter) or if it is a little slick. You step on the gas to pull out and the car stumbles and hesitates until it takes off again. It is very unsettling if you are pulling out into traffic and the nose enters the intersection and the car stumbles and seems to stall.
  • broodhabroodha Member Posts: 1
    I drive a 2008 Toyota Prius and I am intrigued by the news about the 2010 3rd Generation brakes issue, since I have precisely the same problem.

    When I drive over bumpy surfaces, a large pothole, or an area with a dip in the road, the car stutters and lurches and the VSA light flashes. Sometimes the car's reaction lasts for several seconds after hitting the pothole. It seems to exacerbate the problem if I am turning or braking. I should point out that I experience this lurching and stalling sometimes when I am simply driving along at 35 MPH and hit a pothole. So it doesn't really seem to have anything to do with the brakes.

    Like many here, I kind of ignored the problem and assumed it to be a normal part of the vehicle stability function. There have been some situations where it came close to making the situation much worse.

    I also notice the problem accelerating, when the car slips and stutters and the VSA light flashes. This is usually when I am trying to pull out quickly from a driveway or make a quick turn. This is very frustrating (and sometimes scary) on busy roads with oncoming traffic.
  • ericqliericqli Member Posts: 3
    Now that I think about it, you are right: I don't need to have had pressed on my brakes for the car to lurch forward and to have the VSA light come on. What is interesting is that I know for sure that my model does not have the VSA option. So I have a hard time believing that is the intended function of the VSA when it is not even equiped for my vehicle.

    For the other problem, yes it is very frustrating and dangerous in my opinion. I have had several close calls with other cars almost hitting me, when I thought I'd be able to accelerate in time but instead got stuck in traffic. If this issue is pervasive for all hybrid cars, then I am not going to buy a hybrid again.

    I do encourage everyone else to go ahead and file a complaint via NHTSA. So far it seems like Toyota is only considering recalling the 2010 model.
  • jacquescjacquesc Member Posts: 13
    I concur - call the NHTSA and file your complaint. I have had similar occurances as you. However, my accident happened in a situation that was simply my attempt to stop in a traffic jam on a busy city street. Slow speed, pushed the brake with aggression as the car in front of me did. I would normally have stopped with about 4 feet to spare - however, the brakes did not engage until I was four feet away. Some skidding and smash into the car! In no way was the accident due to a lack of my attentiveness as a driver. Now I pay inflated insurance rates and paid my deductible for repair costs. The sad thing is that my insurance company had to pay a significant chunk of the repair costs because Toyota did not pay enough attention to detail (or ignored it). And everyone knows what happens when insurance companies have increasing claims. Everyone has higher fees - this is especially less desirable in this "buckle down" economy.
  • tryingedmunds2tryingedmunds2 Member Posts: 8
    Thanks [wwest]

    re: ABS characteristics: Intuitively, it always seemed to me that, if one could just hold brakes close to the loss of tractrion point, then stopping would be faster than ABS pulsing which has a percentage of no-brake force at all. Thanks for the confirmation.

    re: Unexpected brake-force. Yes, our 2010 Tacoma does have BA (brake assist). I will explore the conditions you suggest will cause the variability.
  • jgriswoldjgriswold Member Posts: 1
    The only thing that is good in the Prius is the gas mileage. We are averaging 47 mpg, less than about 20.00 for a fill-up. Other than that the Prius is very small, even the cabin. It is difficult to see through the back window since half of it is small. Good thing for the back up camera. My engine quit after hitting a "chuck hole" and it was difficult to start. Reported it to Toyota Service and they said "should not have happened, but no notice from Toyota for any problems". The Prius is fine for a small person but not comfortable for the Plus size person. I would not own another Prius.
  • buyamerican2buyamerican2 Member Posts: 16
    You state: " It is not at all unusual for ABS activation to result in elongating your braking distance in a fairly slippery surface by an extraordinary measure."

    The whole purpose of ABS is to shorten your stopping distance, not lengthen it. It is a very effective system on most cars. Toyota apparently does not have the interaction of the friction brakes and regen braking worked out yet. So in the meantime, I will be turning on my hazards when I see a Prius behind me since my car has ABS that does what it is supposed to do (shorten stopping distance) and will thereby avoid getting rear ended by the half baked Toyota if there is a need for some hard braking.

    I probably should also turn on my hazards when any Toyota is behind me to avoid getting rear ended because of some unexpected acceleration event. The roads just aren't safe anymore.....
  • wwestwwest Member Posts: 10,706
    "..The whole purpose of ABS.."

    Is to optimize braking ability along with directional control simultaneously. Read any current owner manual to verify this. Absent ABS during hard/heavy/panic braking there is a clear and certain danger of loss of directional control due to the front tires locking and skidding. ABS activation results in allowing the brakes to exert the maximum level of braking while still allowing the driver to maintain directional control.

    Once someone develops an inexpensive (cost-effective) "linear" brake application servo system to replace the current "bang-bang" system things might improve significantly.

    Until then it would clearly be wiser to disable ABS until VSC detects the need.
  • wwestwwest Member Posts: 10,706
    Go back and read post #132
  • wwestwwest Member Posts: 10,706
    You too...go back and read post #132

    "..It seem to exacerbate the problem if I'm turning..."

    Yes, absolutely.

    If the Traction Control system detects front wheelspin/slip and you are turning then it is QUITE CLEAR that you are applying more engine (HSD) torque to the front wheels than is safe for current roadbed circumstances. This is a FWD vehicle so loss of traction, even momentarily so, on the driven and stearing wheels must be quickly addressed, moreso if the VSC system gets into the act. So in a turn wheelspin/slip will probably result in the activation of both functions, TC and VSC.

    Your Prius has an unusual amount of low speed acceleration torque for its weight along with tires that are primarily designed for low rolling resistance, not TRACTION.
  • wwestwwest Member Posts: 10,706
    Toyota might want to look into the methodolgy of BMW's technique wherein the brake calipers are "pre-charged" with pressure if the rain-sensing windshield wiper system senses rain.

    BMW apparently applies just enough brake fluid pressure to the calipers to bring the brake pads into slight contact with the rotors. That apparently helps to keep the rotors dry in case the brakes needed.
  • michaelhfmichaelhf Member Posts: 1
    You describe the problem very well. I have a 2006 Prius with VSC and I have the same problem on braking - hit a dip or rough spot in the road and the car stutters, the VSC light flashes, and I feel a lack of control for a second or two. I have not had the acceleration problem. I have not had this issue with any other car.
  • seldenselden Member Posts: 22
    I cannot accept that ABS will ALWAYS extend your stopping distance. In perfect conditions, yes, but in conditions of marginal traction, ABS is almost always going to work better. For an extreme (but not unrealistic) example, imagine going down a road where the left side of your lane is icy, and the right side is clear. Hit the brakes with ABS, and the wheels on the left side will pulse, while the brakes on the wheels on the right side will apply full force, something that is completely impossible to do without ABS. I have no experience with Jeeps, but depending on road conditions, applying the emergency brake while also trying to stop quickly can be an invitation to spin; in fact, that is exactly what I do to destabilized a car when I go out to practice driving on ice or snow (in an empty parking lot).
  • wwestwwest Member Posts: 10,706
    "..will apply full force.."


    Talk about "torque" stearing...!!!

    In the situation you describe, disparate braking traction right vs left, there is a design aspect of ABS (and VSC) that prevents the wheel on the higher traction side from applying an inordinant level of braking vs the opposite wheel. To do so might result in the car skidding out of control in the direction of the high traction braking.

    In the very same situation, WITHOUT ABS, I can apply "full' braking, and stear (something ABS [VSC] cannot yet do) counter to the skid to maintain a straight line.
  • revitrevit Member Posts: 476
    The Next Latest to Toyota Comes Next Week:

    By DEE-ANN DURBIN AP Auto Writer
    DETROIT February 6, 2010 (AP)

    Toyota has told dealers it's preparing a plan to repair the brakes on thousands of hybrid Prius cars in the U.S.

    In a message sent Friday night to dealers, a Toyota group vice president, Bob Carter, said the company is working on a plan and will disclose more details early next week. More than 100 drivers of 2010 Prius cars have complained that their brakes seemed to fail momentarily when they were driving on bumpy roads. The U.S. government says the problem is suspected in four crashes and two minor injuries.

    Public awareness of the problem "has prompted considerable customer concern, speculation, and media attention due to the significance of the Prius image," Carter said in the e-mail. "We want to assure our dealers that we are moving rapidly to provide a solution for your existing customers."
  • wwestwwest Member Posts: 10,706
    "..destabilized a car.."

    You're miss-quoting somewhat, if your intention is to "destabilize" you apply the rear parking brake AND crank the stearing hard one way or another. Otherwise applying the parking brake might well result only in your coming to a slow and STRAIGHT stop.

    Back in my wintertime days in MT I often found myself using the parking brake slightly, judiciously, to maintain a straight line going down a slippery roadbed slope. Nowadays ABS would undoubtedly make that a bit easier.
  • wwestwwest Member Posts: 10,706
    "..if one could hold brakes close to the loss of traction point.."

    If we could INDIVIDUALLY hold brakes...

    Yes, that would be "true" threshold braking, using the UTMOST benefit of whatever level of roadbed traction exists SOLELY for bringing the vehicle to a stop or to a lower speed. Should an inexpensive or cost-justified anti-skid control system (CVB, Continuously Variable Braking) ever be developed it could be used to provide true threshold braking AND stearing. Available traction allocated FULLY and SOLELY to stopping or slowing UNLESS VSC indicates otherwise.

    In the meantime...
  • tryingedmunds2tryingedmunds2 Member Posts: 8
    It is a common mis-conception to think ABS improves stopping performance. (It will perhaps be better when compared to an all-out panic stop when all four wheels are locked up by the driver --- this is not really good driving and a lighter foot on the brakes will always outperform ABS)

    ABS is primarily intended to maintain directiional control in an emergency braking situation and it does this BY PERIODICALLY REMOVING ALL BRAKING FORCE to allow tires to periodically regain their grip on the road surface. Since you don't have braking force all the time you can't stop as well as you could if you could properly control the brake force yourself.

    ABS induced extended stopping distances are particularly noticeable on snow, ice and gravel --- just when you need optimum stopping ability. The problem is so pronounced that off-road vehicles often have an "ABS OFF Switch" to make off-roading in mud, sand, snow, icy and hills much safer.

    The 2010 Toyota Tacoma manual covers this on page 195 under "CAUTION' which states "Stopping distance when the ABS is operating will exceed that of normal conditions" and "The ABS is not designed to shorten the vehicle's stopping distance."

    There should be similiar warnings in your owner's manual.

    Hope this helps.
  • chebertchebert Member Posts: 2
    Lots of talk about Toyotas, but I have the exact same brake problem with my Acrua RSX (2006). It's my first car with ABS, so I thought it may be "normal" for the brake pedal to vibrate violently when braking hard and passing over a bump or rough spot in the road. Can't get hold of anyone to voice my concerns. This problem may be more widespread than just with the Prius. It's possible that most people in normal driving would never experience the problem. But if you're approaching a green traffic light that suddenly turns red and you hit the brakes hard while going over a rough spot in the street, you'll wonder if your brakes will ever take hold of the calipers.
  • wwestwwest Member Posts: 10,706


    If ABS detects impending lockup of any wheel due to braking forces it will FULLY release brake fluid pressure from that wheel's brake caliper just long enough, 10's of milliseconds, to alleviate the issue of the wheel actually coming to a full stop. That almost never requires removal of all braking force, "full" retraction of the brake piston.

    Think of it as PWM, Pulse Width Modulation, of brake fluid pressure, in order to "mechanically" maintain an "average" braking force.

    Most "off-road" vehicles will automatically disable ABS and VSC when the center diff'l is locked.
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