Should Toyota acknowlege that the braking issue applies to the gen II Priuses?

I experienced this today while going over a covered sewer drain while coming to a stop for a red light. It was just like sleepawaycampr outlined. The yellow light went on and there was a momentary braking "hesitation" over the drain. It was similiar to other vehicles I have driven.

 

I have two month old Nokian snow tires on my 2009 Prius Touring
Two weeks ago, I was leaving a parking lot, and slid into the car ahead of me even though I had the brake pedal all the way down. Fortunately, there was no damage to either car because the other guy had a rubber bumper, and I was going at a very slow speed, about 5 mph. I had the sensation that I was stepping on the clutch instead of the brake, but of course, the Prius doesn't even have a clutch. The conditions were icy. I don't know if this is a similar problem to what's been going on with the 2010 model, but I figured I would report it. I know what it feels like to have ABS engage, and I felt absolutely nothing. I have tried to send an email to Toyota to report this problem, but it won't let me submit without listing my state and It also won't let me list my state. Ah, well.

 

I recently experienced the braking problem described as applicable only to the 2010 Prius. I had just run over a manhole cover and saw the traction light come on. I was getting ready to turn onto the on-ramp for I-95 when someone from the left lane turned pulled right in front of me. I slammed on the brakes and nothing happened. I assumed first assumed it was the anti-lock braking system, but there was no brake pulsation or response. It scared the crap out of me! I just missed a collision with the other car. When I travel over bumps now, I am very worried about it happening again. I own a 2009/1224A Prius. I thought my problem was an isolated incident until I heard about the recall. Now I am outraged that earlier models were not included.

 

If there was no bump or pothole to trigger this slide, then it seems highly unlikely that this was related to the current Prius issue. And the ice seriously complicates any investigation.

However, it could easily be related to a couple things I have experienced on my older Subaru. First, its ABS has a minimum operating speed, don't remember the number but it is faster than 5 mph. Below the minimum, it is just like non-ABS.

Second, on extremely slick ice, it is possible to lock all four wheels simultaneously. When that happens, my old Suby doesn't know that it is sliding -- all four wheels are behaving identically -- so it doesn't know to trigger ABS. That is a signal to immediately revert to pre-ABS tactics, then abort the trip.

While newer cars are likely better programmed, shrinking the 'failure window', the window is likely still present.

Glad to hear that there was no damage or injury.

 

Also don't forget that no traction means no traction. ABS can't create friction out of nowhere. If your icy surface is sufficiently slippery, you are going to slide no matter what type of brakes you have, unless you have studded tires or chains.

Tom

 

As Tom noted, no traction is an issue, and most low rolling resistance tires have poor traction, expecially below 32 degrees and/or on snow/ice. I switched to serious winter tires to get my prius to drive about like a "normal" FWD with all seasons. Before that I was stuck on a flat road and had to dig out during our first snow a few months ago.

Many have posted that the overactive traction control is to prevent overspeed of the motors. However, after reading the posts on how the system works I wonder about that - there are control algorythms that control the RPMs of the ICE and the motors that I would expect to work even if the tires are spinning. My theory is that the total torque available is fairly high on our Prius (compared to many small engine conventional FWDs) and if you got it spinning good and then hit dry pavement it would probably damage the axles or the planetary drive system that is used as a transmission.

 

But a Prius is exactly that -- a computer-driven car.

Other posters who think their brakes aren't working when they're on ice crack me up, too.

 

I have other non-Toyota FWD cars with Traction Control and ABS and I want to say that, this is the standard behavior of Traction Control in action.

Unlike AWD, TC on FWD will bog down engine power to the wheels when excessive slipping is detected. So it doesn't matter if you floor the gas or not, the TC is governing the wheel speed until it senses real traction has been regained.

I played this with my Prius (on empty streets/parking lot) to get a sense of how aggressive its TC will be, and found that the Prius (my 08 at least, w/stock tires) is no more aggressive than the other cars I used to drive.

So go practice with your Prius TC, ABS and VSC and get a sense of its reaction. Learn how to relieve the gas pedal when TC/VSC is active and keep firm press-action on the brake when ABS is triggered too. This will only help.....Remember, all these 'electronic' safety features are passive and require the driver to work/cope with them, not against them.

 

Really? I have one non-Prius FWD car (2005 MINI Cooper S) and an AWD car (2006 Volvo XC-90), both of which have Traction Control, Anti-lock Brake System and Stability Control (and a few other electronic safety systems) and neither of them exhibit the low speed slippery behavior of the 2nd Gen Prius that has been posted. Perhaps your other cars are also defective?

 

I will bet that I can create a scenario where without stability control, you lose control of the car and with stability control, you maintain control of the car. I might have to use a non-Prius FWD car to do the demonstration, however.

 

This is definite. TRAC has been installed on every Prius since the Gen 1's. VSC has not.

The reason TRAC has been present is that the e-motors are too powerful for the vehicle. They've been tuned down for the G3's but on my 2005 the e-motor has 295 lb-ft of torque at RPM number 1, IOW an instant after putting your foot on the pedal from a dead stop.

Here are two comparisons:
3.5L V6 with 268 HP and 248 lb-ft @ 4700 RPM
4.6L V8 with 310 HP and 327 lb-ft @ 3400 RPM


TRAC modulates the wheel spin at startup because the torque from the e-motors is too great for the vehicle. Without TRAC the tires would burn up in no time flat leaving smoking black streaks at every stop light and stop sign.

VSC was added to most vehicles in the Gen 2's. It's an active accident avoidance feature that reduces the risk of spin-outs and loss of control while turning. It's going to be mandatory in every vehicle from every maker for MY 2012 in the US.

 

This is something that would definitely change the stereotype of Prius drivers. I am imagining 70-year old grandmothers doing FWD burnouts at the exits of local bingo halls.

Traction control is likely there as a measure to preserve the PSD transmission which is likely not built to handle severe shocks to the drivetrain.

 

I feel this on my 2005, too. It should be fixed like all the others.

 

I think the issue on the 2004-2009 (which I do not consider a problem) is differet then the 2010's. The 2004-2009 owners may feel a similar issue going over a pothole or slippery surface but that is normal traction control working as it should. The 2010 issue is an actual loss of possible braking time. The 2004-2009 cars would not been able to have done any real braking because there is no grip on the road. The 2010's are loosing .8 or so seconds of usable braking after the pothole.

Look, all cars with traction control and ABS feel like they are loosing braking over slippery roads but are actually gaining by getting a more sure footing.

 

A discussion with a friend who has followed this braking business has brought to my attention that the only "problem" here is that drivers are not used to the momentary drop in the brake pedal under the very unusual condition when a front tire hits a pothole and then lands on a slippery surface. The owner's manual addresses this and tells the driver to simply continue to apply pressure to the brake pedal, but of course nobody reads the owner's manual. It is not a safety issue and has caused no accidents and has only been reported in fewer than one car in a thousand, but because there are people always ready to make a stink over anything that might create a public fuss it's become an "issue."

Ford builds cars that explode. GM promotes SUVs that roll over as "safer" because they are heavier. Toyota has an "issue" because the brake pedal dips momentarily when there's a pothole in an icy road.

Maybe if people knew how to think, or the news media cared about actually reporting news, or politicians were concerned about anything but seeking votes through demagoguery, the country would not be swirling right down the toilet.

 

Perhaps a new prospective hybrid/Prius owner should be required to get a hybrid vehicle license modification to their drivers license (like you have to do if you want to drive a motorcycle in California - you go to a week's worth of classes and hands-on driving experiences to learn how to operate a motorcycle on public highways)?

I wonder what that would do to hybrid sales?

Or, the manufacturers could just build cars with safety systems that performed like the non-hybrid cars. What a novel concept. Daaayum.

 

Posts earlier in this thread, or at least one of the 7 (yeah, overkill I agree) other threads have owners that claim that the braking behavior has been an element in accidents or near- accidents.

Sorry Daniel, but it really is disingenuous to say both "A hybrid is just like a normal car, except it uses less gas" and "you need to learn to drive a hybrid properly." Whether you like it or not, there is a set of behaviors that normal individuals, with years of driving experience expect. The momentary (real or perceived) loss of braking pressure midway though the brake pedal movement is extremely counterintuitive to this mental model of how a normal car reacts.

 

They stopped building the cars that explode a long time ago. Now they just catch on fire. :madgrin: