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Toyota Prius Brake Problems

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  • wwestwwest 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.
  • 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 Posts: 21
    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 Posts: 10,706
    "..will apply full force.."

    NOT..!!

    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 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 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 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...
  • 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.
  • 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 Posts: 10,706
    "...BY PERIODICALLY REMOVING ALL BRAKING FORCE.."

    Well....NO.

    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.
  • wwestwwest Posts: 10,706
    "..I thought it may be "normal"..."

    You thought correctly.

    It is perfectly normal for the brake pedal to vibrate violently while ABS is in use.

    The problem being expressed concerning ONLY hybrid vehicles is the transition from regen braking ONLY into friction braking at the instant impending wheel lockup due to braking is detected. If the ABS "event" is momentary then all that the driver feels is the brief "lurch" forward for the 100 or so milliseconds it takes to release regen braking and then extend the brake pistons outward to bring the brake pads into contact with the brake rotors.

    Since the brake pedal never goes into violently vibrating mode the drivers see this "lurch" as an anomaly when it reality it is uniquely SOP to hybrids.

    And yes, on a highly slippery downslope I have often had to apply the e-brake to bring the vehicle to a final full and complete stop.
  • With my Acrua, the period of violent pulsing of the brake pedal and loss of braking action could be measured in seconds, not milliseconds (1-2 seconds). Of course, my car doesn't use a flywheel for regenerative braking like the Prius, and maybe it still is normal to lose braking for a second or more when slamming on the brakes over a bumpy road in an emergency stop.
  • revitrevit Posts: 476
    Toyota 4Runner exhibits acceleration, brake symptoms

    Toyota’s massive recall of many of its high-volume models has, surprisingly, led to few credible reports of similar symptoms in non-recalled models. Yet a 2004 Toyota 4Runner in California is said to be experiencing exactly the same issues as its recalled brethren.
  • wwestwwest Posts: 10,706
    The 100 or so milliseconds quote relates to the transitional time for a hybrid to go from regen braking to frictional braking. Vibratory motion of the brake pedal under ABS activation will last as long as the brakes are applied and any wheel is tending to lock.
  • My 2005 Prius does exactly what yours does. I have noticed those problems since I had the car. I also noticed that if you are going down a slight hill it also lurches and slips too. I always think I need new tires with this car because of that slipping issue. One time my brakes failed when I was on a trolley track with cobblestones in a light rain. THank goodness no one was there. I have filed a complaint with nhtsa.
  • A question

    ABS is capable of PWM, Pulse Width Modulation, down to 10's of milliseconds is good, but does that allow enough time for the wheels to grip and the driver to take advantage of the grip? I have a feeling the Mark/Space ratio might have to be say, 70/30 of brake/"no"-brake to maintain steering. I see that as about 30% less stopping ability. Realistic?

    (I've seen estimates of 20% longer stopping distances, but I don't know how this was measured.)
  • I own a 2007 Toyota Prius and have experienced occasional momentary loss of braking (my foot firmly on the brake pedal) while driving over a bumpy surface. While braking over small pot holes, railroad tracks, rough patches, etc., the car seems to lunge forward apparently as the brakes release for a split second (approximately 1/4 to 1/2 second). The road conditions can be wet or dry. At the same time, my traction control light will flash on and off until the road smooths out. That split second is enough to cause an accident with the car in front of me if I don't give myself extra room or slow down prior to the bumpy condition (1/2 second at 20 MPH = 15 feet of unwanted travel). I drive over the same railroad tracks just prior to a traffic light every day and I have had to adjust my driving habits to keep this dangerous, additional stopping distance from reoccurring. I have seen similar complaints with earlier models up to the new 2010s on this and other websites. Some believe that this is a software delay that occurs when the braking switches from the electro-magnetic to the mechanical braking system. I would hope Toyota is aware of this (what I consider a design issue) and that earlier models will be included in the recall. So far it's only 2010 models. If you are experiencing the same problem, please contact the National Highway Traffic Safety Administration Vehicle Safety Hotline at 888-327-4236 to make sure Toyota gets the word to include all affected model years. You may also report a safety complaint at: http://www-odi.nhtsa.dot.gov/ivoq/index.cfm
  • revitrevit Posts: 476
    Toyota Prius braking issues may predate 2010 model; other problems reported :lemon:

    Toyota Prius braking issues may predate 2010 model; other problems reported

    Could the apparent braking problems reported on the Toyota Prius – which Toyota admits was an issue on the current model prior to being resolved earlier this year – extend past the recently released 2010 model? According to TheDetroitBureau.com, the answer is a resounding... maybe.

    The third generation of the popular hybrid hatchback hit the market in 2009 as a 2010 model, and some 300,000 vehicles are thought to have a software glitch that could cause the car to lose braking power for up to one full second under certain circumstances. But that's not all. Apparently, reports of braking issues have been pouring in since 2005 or even earlier. If true, over a million second-generation Prius hybrids could potentially be affected.

    Perhaps it's worth mentioning that previous electronic issues have also been reported, such as headlights that burn out too quickly and malfunctioning traction control system. As pointed out by TheDetroitBureau.com, "ABS, traction control, electronic stability control and various other technologies all rely, at least in part, on braking to improve the stopping, handling and stability of today's cars, including Prius."
  • Please see my previous post #81
    I took my Prius in and had them look at it on Dec 15th a couple of weeks after I had the accident. They said that everything checked out fine and that it was probably my anti lock brakes kicking in(I moved to Seatlle from Minnesota and I know what anti locke brakes feel like, that wasn't the problem). Since then going down the same hill the car has accelerated when going over a pothole in the road. I called Toyota back and they said that my car is not part of the recall and that when they looked at my car in December they checked the brakes and the accelerator and all checked out! I feel like there is not much else to do. I called them again today and left a message that I want them to take another look. My insurance company said to just keep bugging them. After reading the other posts, the service guys at Toyota must have been told to tell people that they have never heard of this problem! I also feel Toyota should fix the bumper that was dented from the brakes failing to work! URG
  • Have you filed a report with the NTSA? They have an online form. I personally believe you as someone who's had the same problem.I think unless people start to complain to the right people, this will be swept under the rug. I encountered the problem one time in my 2007 Prius in December during an ice storm. I live in minnesota and am all to familiar with the feeling of Anti-lock brakes on ice. This was a completely different experience. I had it happen a second time yesterday. I hope it never happens in a busy intersection.
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