PDF file of the official CHP report on the Sikes affair

Correct. Four wheel disc brakes were standard on most Gen II Prius other than those in North America. The new Gen III Prius has four wheel disc brakes.

The Prius involved in the San Diego indecent was a Gen II with drum brakes in the rear. Because of this, if the rear brakes are fried, they won't work even if actuated by the parking brake lever.

You are also absolutely correct that the parking brake is cable operated, so it does provide some backup in case of a total braking failure of the hydraulic braking system, although the power of the parking brake is severely limited by nature of this cable operation and the fact that only the rear brakes are engaged.

Once again, this cable operated brake is a parking brake, not an emergency brake, not to say that you can't use it in an emergency.

Tom

 

See below:

 

Sorry, showing my age, "emergency" brake....should have known better than to use the term "e-brake" as nowadays that has an entirely different connotation.

I would still say that applying the parking brake might just make the difference, especially if the rear frictional brakes are otherwise being compromised via ABS.

 

In some very specific cases, yes. Most of the time the parking brake is pretty ineffective. Of course, if my other brakes weren't working, I'd go with the parking brake in a second.

Tom

 

The information is at techinfo.toyota.com. 2010 Prius recall AOB.

"..in the worst case, this may lead to an increase of vehicle stopping distance and thus raise the possibility of a crash.."

"..The condition is caused by improper programming of the ABS Electronic Control Unit (ECU). Due to this programming, there is a possibility that the braking force after ABS activation may slightly degrade as compared to the braking force before the activation..."

...until the remedy is completed on the vehicle Toyota advises drivers to depress the brake using more firm pressure..."

I guess I was wrong, the loss of braking might be for an indefinite period, not just 1-2 seconds.

"..improper programming..."

A rather straightforward admission by Toyota..??!!

 

Did anyone claim to have experienced longer than 1 second? Bob's accelerometer recorded 0.7 second.

(I'm excluding the claims on ice and slick winter surfaces, which seem to be a different problem.)

 

You reached that conclusion for real?

 

Well, someone's gotta say it. I smell another troll.

M.O. fits. Check the sign-up date and posting pattern.

 

Improper programming was what I said above. Nothing in what you pasted says 1-2 seconds (let alone indefinitely), nor does it discuss any accidents attributed to the programming.

 

I agree it can't be unlimited drop out. The car will eventually hit something or stop even with no brakes. Although without knowing what the bug is, its hard to determine what the worst case is.

here you go on a source for the accidents
NY Times Advertisement

I'm sure some will repeat that there is no bug, or say that those accidents aren't confirmed, etc. Just let it go. Toyota had a bug. drivers like me didn't report it because our driver error need an excuse. It isn't part of the way regen brakes need to work. Bugs don't help gas mileage, etc.

 

The "braking problem" is not a safety issue, or Ford would have had to have a recall. Following too closely is a safety issue. Anyone who responds to the brakes not slowing the car by pulling their foot away from the pedal probably shouldn't be driving.

At least in my Gen II Prius, the "problem" is no different than what I experience with my 01 Chevy Blazer. It's ABS.

 

The document clearly implies that if the driver doesn't react to the "slight" decrease in braking force due to the ABS programming flaw by increasing brake pedal pressure it will continue indefinitely.

Only the folks who have experienced the problem can relate to us just what "slight decrease" means.

 

Your Gen II Prius does NOT exhibit the long braking gap that the 2010 model sometimes does. The Gen II only exhibits the momentary, 100-200 milliseconds, braking gap when ABS activates, INITIALLY activates.

 

Wonder if the programming bug had something to do with the 2010 switch to disc brakes on the rear?? Obviously different frictional vs regen braking computation would have been required

 

Without knowing the bug, its really hard to say. I would assume that if the bug is in the 2009 prius, increased regeneration from the mg motors would amplify it along with different friction braking profiles. I would say it is more likely that the same bug is not in the previous model prius. I have no knowledge of that software, and do not know if there are any serious bugs or bugs at all.

As to the point of whether this was a safety issue, I don't want to debate it. I would not put any belief that fixes that are recalls are safety issue, or those not recalled but fixed do not involve safety. There is a propensity of some to have poor statistical reasoning. If something happens infrequently, the fact that you have not experienced it, has no bearing on whether it exists or not. This is especially true if you do not have that make or model. The loudest voices for driver ineptitude on the brake issue were from those that did not own Gen 3s. I tried to put out a balanced article that reported crashes, it took all of 5 minutes to find. The first one I pulled up was quite biased against toyota. I would have preferred a SSB and full cooperation with the safety agencies. I also wanted to post something so that fud on these forums would not stop people from getting the software updates.

The reason why this issue is important is because software is a possibility in uninteneded accelleration which is a safety concern. I would say that it needs to be investigated. This is regardless of whether sikes is an incompetent driver or a hoax. I think hoax is most likely, but there is a possibility of lack of competence. I don't think anyone reasonable would look at the evidence and assume that a normal driver would not have had a problem stopping the car even with unintended acceleration.

 

For me, thinking as I was that the parking brake was a separate drum type brake on the inside of the rear disc brakes I would have probably tried the parking brake much earlier. I like to believe that I would have heard, and recognized, the ABS "hammering" of the rear brakes and acted accordingly.

I do wonder what would have happened had Sikes slipped the system into neutral. But even I would have approached that measure with tripidation with the drive system in WOT runaway and the brake system not "pulling" it out of that mode.

When we train for a pilots license we practice emergency procedures over and over again so, hopefully, they become second nature even in a panic situation.

I have had Panic braking situations wherein I sincerely wished the ABS would stop working so the car would come to a stop before colliding with something. So I can see where a "gap" in braking in the 2010 Prius might be a frightful situation.

 

Sure. The problem is not just that he didn't put it in neutral, it is that he pumped the brakes. Toyota says that he was pumping with light force, I'm not sure about that, but he definitely was pumping instead of standing on the brakes. If you had been in the situation I hope you would be pressing as hard as you could.

The parking brake will engage independently of any computer, abs, or other problems, so your instinct would have helped even if you were pumping the brakes. You can't pump the parking brake, only engage and disengage. Given the reports, after talking to 911, I would hope you would try neutral after the 3rd or 4th time they told you it would help.

I agree completely about panic situations and training.

 

Sorry, pumping the brakes, when they don't appear to be working, or appear to be not working properly, is a long learned instinct for me. In any case I suspect that I would have also "jabbed" the gas pedal not just a few times in hopes it might "release".

254 times in 20-30 minutes, more like a computer glitch to me.

And remember that the early news was that BOTH the gas pedal and brake pedal had been "stroked" 250 times.

 

I still maintain these were driver errors, even if it's a bug, simply because 1 second delay isn't long enough to be the cause of the accident and can be eliminated entirely by pressing the brake harder. They simply didn't stop in time, and they're some of the many rear enders that happen every day.

One can easily confirm those accidents by scanning the locations of the accidents to look for imperfections in the road. No imperfections = no possibility that they can be attributed to the regen to friction braking delay.

 

Very good point.

I don't think it was a Hoax. I think the car was in malfunction state and very difficult to duplicate.