Poll: Are Prius brakes a problem?

Your statement is almost an insult to those of us who don't practice what you call "free-fall braking" and have had the problem. I have experienced it 3 times in 11K miles and the first time put my heart in my throat. The next two times I knew immediately what was wrong and just pushed harder and further on the pedal. But it did take longer to stop.

I am amazed by a few old time died in the wool Toyota supporters who don't even own a Gen3 Prius and think this problem must be the fault of the driver. We are not just a bunch of mean people who are picking on your favorite car company. I owned an '05 Prius and put over 30K miles on it on all kinds of roads and never had this problem.

I know exactly what the transition between regenerative braking and friction braking feels like, although this problem happens at about the same speed and may be related it is definitely not the same thing.

I can live with this problem, I've owned cars in years past that almost didn't have brakes, but I shouldn't have to live with it. Brakes should work pretty much the same way each time and the driver should be able to have confidence in them.

 

Yeah, I'm getting that vibe a lot too. I love my Prius and hope Toyota looks into this matter and resolves it so EVERYONE can be happy and feel secure and safe in their vehicles. I don't think the resolution will necessitate a loss in FE as some fear...and if it does, I can live with a 0.1 mpg decrease if it means someone's life is made better by NOT getting in some kind of horrible accident that may be caused by this condition. I just don't get some attitudes...

 

I can't answer the poll as I don't have one of the cars, but a
look through the New Car Features stuff shows me that Toyota
changed the braking system between genII and genIII in a pretty
radical and not necessarily improved way. In cutting down the
number of solenoid valves in the actuator and returning to a more
traditional master cylinder/booster/balancer setup, they may have
lost several of the genII's by-wire-until-you-can't advantages
and ability to make transitions smooth. This is very puzzling,
as the genII system looks quite well thought-out and the genIII
system is downright confusing.
.
_H*

 

I just repeated the same tests again that I spoke of in my earlier post using my wifes Corrolla and my Prius.

The sensation of loss of braking, speeding up, etc is very noticable and a bit un nerving but yet I have the same results. The Prius stops shorter then my wife's 2009 Corrolla with ABS.

How can this be a safety issue when the Prius stops in less the distance then the Corrolla?

Is it truly fair to say the PRIUS should act as a conventional car?

If that were true then shouldn't a conventional car get 50 + miles to the gallon?

Shouldn't a conventional car turn it's engine off at a stop light?

I know i'm new to this forum and am not looking to upset anyone, I'm just asking folks to be a little more open minded. The Prius is different technology. Conventional cars do not function as the Prius does and Prius doesn't function as a conventional car does.

I to was worried about the braking sensation or shall I say the loss of, but I can not dispute the fact that even having this sensation the stopping distance is shorter then 2 perfectly working conventional cars.

 

i agree with you GeoDesign. what others are describing is a "symptom" which to me is not a problem. a car with abs, traction control, and vehicle stability control will brake differently than a conventional car.

the symptom may not feel right, but so what? if your car stops in a shorter distance and is more controled, who cares? the car is safer... the problem is some drivers are not used to the feeling or sensation when all the technology kicks in.

i'm sure others trying to answer the question "why the Prius brakes the way it does" will have more to say on this subject.

:yield:

 

Just because the Prius is high tech and different doesn't mean it should be permitted to have a braking system that can't be counted on to stop the car the same way each time. The problem being discussed here is an intermittent problem, it only does it once and a while and it can really catch you by surprise when it happens. The fact that the Prius may stop quicker than a Corolla is not really relevant to this issue. We are talking about a problem that occurs sometimes but never shows up when you are making an emergency stop.

I don't think anyone is going to die because of this but, as previously noted, it can increase stopping distance under some circumstances. We shouldn't have this kind of problem, especially in a high tech car.

 

the Prius will never stop the same way each time. brakes only will be different than brakes + abs, which will be different from brakes + abs + traction control, which will be different from brakes + abs + traction control + vehicle stability control.

your issue is you want the Prius to react the same way each time. sorry, but i can guarantee you that will never happen... because each application of brakes may be different. in good weather and good roads, you will have a consistent stopping experience. in bad weather and bad roads the technology will do what is best to stop the car, and it won't feel the same as braking in good weather and road conditions.

the one thing that will be consistent is the brakes will stop the car faster than a car without the technology present in the Prius.

again, not having the same "feel" each time you brake is not a problem. the car stops faster with technology than without.

 

The fact that the Prius may stop quicker than a Corolla is not really relevant to this issue.

Tumbleweed,

I beg to differ to your above statement. The intire propose of my tests was to recreate the sensation of the loss of braking. I recreated this each and everytime and the result was the same. Everytime i hit a rough patch it felt as if the brakes had released but the stopping distance remained shorter and precise Compared to the Corrolla. The results were the same in panick stopping, normal braking, etc.

Anyone in my area (Henderson, NC) are more then welcome to come my home and use my road and see for themselves. Just ask and we can arrange it.

 

I was not aware that traction control or VSC entered onto this problem? I realize both systems use the brakes but why would they be active under the conditions we are discussing in this thread? ABS on the other hand might well be part of the problem since people with other Toyota models have reported the same thing.

This isn't so much a problem of different amounts of pedal pressure being required under different road conditions, we all should expect that. This is a problem of greatly decreased stopping power for what seems to be almost a full second with little change in road conditions.

I really think this hasn't much to do with the fact the Prius is a high tech car, in fact maybe it needs to be a bit more hi tech. Referring to Hobbit's post above it seems Toyota may have made changes to the braking system that exacerbated this problem. I drive this Gen3 car on the same roads and at the same speeds as I did my Gen2 and I never had a problem even remotely like this with the Gen2. But others have reported the problem with the Gen2 so it does exist in those cars as well. The poll might give us a better idea.

EDIT: Poll results so far indicate about the same percentage of Gen2 and Gen3 cars have the problem/issue.

 

You could answer for the Gen2. I think that Bob intended the poll to apply to both Gen 2 and Gen 3 which is why the categories are repeated twice.

I think it is interesting (in this thread and the other more alarmist thread) that there are owners who have owned and driven both versions but seem to disagree on whether the issue (transition from regen to friction braking) is the same, worse or better in the new model than the previous one.

 

I too have one spot one block from my home where if I apply the brake as I'm going over this spot, the vehicle feels like it lurches forward rapidly, causing me to apply more brake. It's like the brake lets go. It's a slight rough spot with a dip in the road. I can reproduce the problem every time. I've learned to slow down before the spot, so I can go over it without the brake. This strikes me as very dangerous, especially for new owners, who have not experienced the problem. It can lead to a very excessive over reaction. I think Toyota should be extremely interested in resolving this problem, which is clearly a software issue to do with the braking system logic.

 

Sorry, there was no intent to belittle your efforts, in fact I applaud them.

I have tried to recreate this "loss of braking issue" since the first time it happened to me and have been unable to do so. I even went back to the same stretch of gravel road where it happened and it just wouldn't repeat. Then I did have the issue again under different circumstances on paved roads but could not repeat that either.

I would also point out that just because the Corollas you tested didn't have this problem (although the 04 didn't do to well on the panic stop) doesn't mean none of them have the problem. According to poll results so far about 2/3 of the Gen2 and Gen3 Prius have no problems either. But Jayman from Winnipeg reported in another thread that his FJ Cruiser has the braking problem.

I hope your test results are typical of all the Gen3 Prius, I would like to think this is a non-problem. But others, on one of the other threads, have reported a 44 ft increase in stopping distance. But I think that was calculated rather than measured.

I would love to take you up on your offer and try it on your road , unfortunately it's a bit far. The snow is almost gone now so maybe I'll go out and try it again tomorrow.

 

Like GeoDesign, I too have a spot near my home, where if I apply braking as I go over it, the vehicle feels like it lurches forward, like the brakes let go. The spot is rough with a dip in it. It is necessary to slow down here, as it approaches a small turnabout. I've learned to slow down enough, prior to the spot, so that no braking need be applied, but this strikes me as a potentially very dangerous bug in the braking software; especially, for new users. I can reproduce the symptom, every time.

 

I disagree.

 

Tumbleweed,

No offense was taken, no need to aplogize. I'm just sharing my findings. I certianly agree that it is alarming and catchs most by suprize. I believe however that I have answered my own fears and just am accepting the fact that this is the way the car behaves. As humans we tend to like to be in control and I believe the real issue here is that in those instances we are not, the car is. We just have to learn to trust it.

 

FWIW, I was confused by how to answer the poll and had to reread it a few times. I believe I answered correctly and afterwards, I'm pretty sure I totally understand it now.

I think there actually need to be maybe at least 4 separate polls to make it easier. There should be two polls that go in the 3rd gen section (intended only for 3rd gen owners) w/one asking about the frequency and the other asking about the "scary, can live with it, no big deal question". The 2nd gen section of the forum should be asked the same two questions but only intended for 2nd gen owners.

Yep, I also appreciate Bob's efforts here.

That would be another interesting poll(s).

One guy at my work's Prius mailing list (I used to work with him ages ago) says that the effect is worse on the 3rd gen than his former 1st gen. This contradicts what some people have said. But, it's no big deal to him and he's used to it.

 

If the brake lets go, as you're braking, why would this not be considered dangerous. Just curious as to why you or anyone would think otherwise?

 

I'm have a gen III and have not witnessed the problem.

I haven't driven on many rough roads yet and am sure that the problem is real for some drivers (it may be defects in some, or design). Also I have put stickier tires on my car, so I haven't seen the VSC kick in as it did on the stock 15s of the car I test drove.

I don't particularly like the brake feel, but am getting used to it. I'm sure toyota could have done a better job. I don't think it affects safety.

Note abs and vsc do not help you stop faster, they keep the car in control to maneuver (vsc also helps prevent rollover, but that is mainly a problem in taller vehicles).

GeoDesign, that is good news that it brakes consistantly when the problem occurs. Is it the vsc that kicks in? It is bad if you stop noticably slower than the prius would on normal pavement in the conditions dry/wet/snow. The car shapes your expectations.

I do think it doesn't matter about the corolla taking longer to brake, most maybe all cars in its class brake faster.

 

I think I see the same thing here that I have seen on the other "braking problem threads". Some of us think there is a problem and it needs to be fixed; others see no problem at all or a minor problem that anyone could live with. I think the poll results will bear this out.

So what is really going on? I propose that not all cars that have this problem have the problem to the same degree.

Some may only feel a small decrease in braking for a couple of hundred milliseconds and think "that was nothing, what's all the fuss about."

Others have felt an almost complete loss of brakes that lasts for nearly a whole second and think, "wow this needs to be fixed".

Maybe none of us are completely wrong and we are just seeing different parts of the elephant?

 

Tumbleweed,
Well said.