Last post on Sep 03, 2013 at 5:22 PM
You are in the Toyota Prius
What is this discussion about?
Toyota Prius, Brakes, Hatchback, Sedan
Go to NHTSA to file a safety complaint.
Or call Monday-Friday (8 am to 8 pm ET) (888) 327-4236 TTY: (800)424-9153
#156 of 370 Re: 2006 Prius Braking problem [michaelhf]
Feb 08, 2010 (8:41 am)
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.
#157 of 370 Re: 2010 Prius Owner with Brake issue [tryingedmunds2]
Feb 08, 2010 (9:04 am)
"...BY PERIODICALLY REMOVING ALL BRAKING FORCE.."
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.
#158 of 370 Re: 2006 Prius Braking problem [chebert]
Feb 08, 2010 (9:18 am)
"..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.
#159 of 370 Re: 2006 Prius Braking problem [wwest]
Feb 08, 2010 (9:40 am)
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.
#160 of 370 Toyota 4Runner exhibits acceleration, brake symptoms
Feb 08, 2010 (10:27 am)
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.
#161 of 370 Re: 2006 Prius Braking problem [chebert]
Feb 08, 2010 (12:41 pm)
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.
#162 of 370 Re: 2006 Prius Braking problem [ericqli]
Feb 08, 2010 (6:08 pm)
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.
#163 of 370 Re: 2010 Prius Owner with Brake issue [wwest]
Feb 09, 2010 (5:31 am)
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.)
#164 of 370 2007 Toyota Prius with Braking Issue
Feb 09, 2010 (6:07 am)
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
#165 of 370 Toyota Prius braking issues may predate 2010 model; other problems reported
Feb 09, 2010 (11:26 am)
Toyota Prius braking issues may predate 2010 model; other problems reported
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."