The brake problem is back (or did it never go away?)

+1

It was raining when I recently had to do a panic stop (a car changed into my lane without looking). Once the adrenaline stopped pumping and I had time to think through the incident, I realized just how admirably the Prius had performed. Actually, it handled so well, I was able to "sit down" on the horn and still maneuver with one hand.

 

I also agree. I nearly smoked two kids a couple weeks ago. I was in a shadier part of town, and these two delinquents were doubling on a bicycle when they darted out from behind a car at a busy intersection. I slammed the brakes, and I was brought to a halt in no time with barely a chirp from the tires. ABS may have kicked in briefly. I double checked and made sure I had the green light. I don't feel ashamed to say it wasn't the kids I cared about. I was thankful my car wasn't damaged or the inconvenience they would have caused me with my insurance co, police, paramedics, and possibly news reporters. BTW, the "kids" looked about 15-16. They know better.

 

Have put 4600 miles on my Prius and have experienced the "braking problem" twice, both under similar circumstances: just beginning to brake for a light ahead and on the brakes lightly with an expectation of needing to brake harder. The first time it was on a short stretch of road that was being repaved and not quite smooth, the second, a shallow but rather elongated pothole. Car felt like it sped up, but in reality, was just not braking as fast as it would have under normal circumstances. Stepped on the brake harder to regain braking control, and brought the car to a stop with no problem.

This is just not a problem if you are aware of what is going on and what is actually happening (thanks to everyone on these boards!). Keep the circumstances in your head and it is just not going to be an issue.

 

I have been talking to Toyota about this issue since I got the car almost a year (and 15,000 miles) ago. Bottom line - I was told to "live with it". They know about it and will not fix it. The ABS flash just made it a little less egregious, but did not "fix" the problem.

 

The problem never went away. I still get skips in the brakes when I hit hard bumps, so I just go over them slower and you just have to be careful.

 

They wouldn't care if the car only had 15 miles on it and you just left the dealership lot. Once you buy the car and give them your money, the dealership could care less about their customers.

That has been my experience at every one that I have been to. Not to be negative or anything, but that's largely the reality. They are salesmen after all.

 

I'm not sure there is anything to fix, short of eliminating modern ABS. Therein lies the root of the conundrum.

Tom

 

I totally agree. The braking inconsistency that was supposed to be addressed by the recall is now only shorter in duration but still apparent to this driver. In a sense it hasn't gone away.

 

This is the kind of thing that you have to deal with any time you are on the bleeding edge of new technology.

I still dont see how this quirk manages to keep anyone up at night or make them scared to drive their car, let alone sue Toyota. When it happens it feels a little weird, but unless you are literally up someones tailpipe, or driving waaaaay beyond the standard performance envelope for a car of this kind, its really a non issue.

Ill take Toyota's minor software quirks over GM's eastern bloc built CVT's grenading after 20k miles, or Honda's IMA batteries cooking themselves over a matter of 2 years. Any time you push the envelope with new engineering, where complex systems have to interact with each other in split seconds, there WILL be quirks. As long as its not the "IM SLAMMING ON THE BRAKES AND IT WONT STOP!" kind, im willing to accept that as the price of admission to a brave new world.

 

theloop82,

I really like your post. you hit the nail right on the head. No, I'm not a spammer or troll (as you can see, this is my 341st post), but it's one of my shortest (if you've ever seen any of mine before).

Ken (in Bolton,Ct)

 

No, not all cars with ABS have the problem. My '98 SAAB has ABS and it works just right. It never releases just because it hits a bump. The regen stops when the Prius goes over a rough surface, causing the car to feel as if the brakes have released. This is, was, and will be a problem.

 

Not all cars with ABS have it, but many non-hybrid cars do. Regenerative braking is neither necessary or sufficient to cause this problem. Perhaps regenerative braking exacerbates the problem, but it is not the root cause. It is, at its core, and ABS issue. Toyota's electrically assisted brakes seem prone to this issue. The FJ is a good example, and it certainly does not have regenerative brakes. It does, however, use electrically assisted ABS brakes.

Tom

 

My 2000 Corvette, 2000 GMC Z71 and 2002 Chevy 1/2ton 2wd had the same issues when hitting a bump while braking. I'm glad to hear your SAAB didn't have the problem.

 

My CR-V does this too. I never understood why, so thanks all!

 

I've only had my Prius V for about a month now and have noticed this brake "chatter" problem twice. It happened to me again today. I was braking for a stoplight, and the road was a bit rough. That's when the brakes chattered for about 1 second as I was moving over this rough pavement. Glad to hear it's an ABS - regen issue. I guess we have to live with it. Otherwise the car is amazing! Loving every minute of driving with it, and laughing at the gas stations I pass by. So far averaging 4.4 L/100km (sorry, Canadian mileage units) or about 64 MPG!

 

Regenerative braking is actually a major issue since the regenerative braking torque is applied by the transaxle, through differential gearing, to the front wheels. So if one front wheel slips the other front wheel loses torque as well. Possible ways to remediate this are (1) to install a limited slip differential or (2) to add regenerative braking to the rear wheels with one or two additional MG's. Software cannot eliminate this phenomena. My overall take as an owner is that the phenomena is alarming but not dangerous since it only increases your stopping distance very slightly.

Vehicles with (4) channel ABS systems controlling hydraulic brakes have very little loss-of-braking sensation. Vehicles with (3) channel systems, mostly trucks and perhaps the FJ, have more of a sensation.

 

With due respect, I drove German cars of different types with Bosh ABS for many years and never experienced any problems. So far we have had no problems with the brakes on our Oct. 2011 build date Prius but the problems described with the 2010 Prius brakes would be unacceptable to me.

 

I think there is a little missunderstanding here. I will explain as best I can and hope you see my logic.

The car has ABS (anti block system). Abs job is to prevent the wheels to lock up(stop spining) while the car is still moving, because if they lock up you can't steer.

Now most think of abs as the "THUDTHUDTHUD" kind of system, but look more generaly. The only point is to prevent wheel lock up. So anything that can lock up the wheels should be monitored and controlled by the abs system to reduce the breaking power if the wheels lock up. This includes the electric motor. The only problem is that you cant reliably controll the breaking power of an electric motor in slippery conditions. So the smart thing to do when slipery conditions are detected is to completly disable the electric braking and switch to normal friction braking with classic abs (which works in all conditions).

Think of this as a panic mode of the car, which activates when either the wheels lock up or you break really hard. The only concern for toyota here is safety and the only way to ensure proper braking behaviour is to let go of regenartive braking when you cant guarantee it will not lock up the wheels. The transition isnt smooth beacause the only concern is safety and the car cant know if you hit a pothole or started driving on ice suddenly.

Regarding the patch that "fixed" this little "problem":
The real problem was, that after a pothole event the car would stay friction only for a prolonged period of time. After the patch it now returns to normal after a few seconds(before I think it stayed friction only until you let go of the pedal).



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