Recall for brakes DID NOT fix the problem

I didn't know bmw had regenerative braking for over 9 years. I learn something new everyday!!!!

 

Finally noticed something like this with my Prius, which has had the recall. Coming to a turn where some road construction is underway, I was braking about half scale with regen when I went over a bump and I felt the loss of deceleration for a very brief moment, but it was very mild. A little extra foot pressure and the rate of decel was quickly restored.
I can only imagine this being a big problem if I were really tailgating someone or otherwise driving in a very non-conservative manner.
Still trying to find a situation where it would be "dangerous."

 

That is the general consensus among those of us who have lived with the GenII Prius for 100k miles or more. It has never been an issue with me nor has it ever created an unsafe situation, but people like to complain so this is just another outlet for them I suppose.

 

I've never felt it in my boat either.

Tom

 

I have been sitting on this couch or years and never noticed it doing this either.

 

Only the recliner couches have it, and with most of them you have to pull a hand lever to make it work.

Tom

 

I HAVE noticed many instances of sudden acceleration when sitting in the throne room but fortunately it doesn't last long and pulling the hand lever takes care of it.

 

I have had the same problem. When I bought my 2010 Prius in Feb. 2010 the dealer did the "abs actuator ecu update" and gave me a paper documenting it. The brakes operated normally for the first four months. Over the last two months my wife and I have each independently noted on four occasions that the braking briefly disappears when going over a rough patch of road. This has never happened to us with any other car.
I called our dealer and was told "this sounds like normal braking". This is quite disappointing because I had understood from posts here that the problem was fixed, but recent posts in this thread indicate people have had the same experience as I have had.

I am going to take it in to the dealer to make sure the ecu update has been done, and if they cannot fix this problem I will certainly be on the phone to Toyota about it.

 

My bet is that you have felt this sensation before, but the pulsing pedal and grinding noise from under the hood distracted you and also yelled "ABS HAS ENGAGED!", so you didn't notice the decreased braking that was occurring because of the transition to ABS and how it works.

The Prius will engage ABS with zero noise or feedback at times -- or maybe all the time, I've never had it kick in with pulsing and grinding like my older ABS cars. And the Prius may kick in ABS at a lower threshold than other cars, because of the switch that must occur from regen braking to friction with ABS.

Combine the two and you'll end up with a quiet ABS kicking in under conditions that your older car either would not use ABS or would have made all the sound and fury that would've distracted you from or justified what you were experiencing.

Heck, I tried to recreate the problem back when it was first discussed and could not. Finally, after many months, I was braking in the rain on a metal plate in the road and something happened, and then about 10 seconds later I realized, "Hey, that was probably what people are talking about". To me, the feeling was brief and my mind totally justified it instantly as a bit of slipping on a slippery surface.

I've experienced a brief blip since the braking was modified by the recall, and it was literally a 1/5 second pulse or something. Who knows, I may have experienced it dozens of times and it didn't even register?

I really think it boils down to: 1) regen-friction transition with silent ABS kicking in, and 2) drivers who have been raised on ABS, or in non-icy conditions, and never really had to ride the brakes on uneven or slippery surfaces.

 

As I said in another message, I think it is a real issue, but there is a LOT of varying levels of perception at work. I may have experienced it dozens of times and not even noticed it, while someone else who is used to noisy ABS and smoother/non-icy driving experiences something really spooky and unsettling, perhaps freezing a bit in panic and not pressing harder on the brake.

I started driving in the early 80's and went to college in upstate New York, so braking varying a bit under varying conditions is natural, and my foot adjusts naturally without even thinking about it.

(Actually, with my first ABS car, this ingrained habit might've actually caused an accident: I was sliding on ice and modulating the brakes when I should've pressed the brakes through the floor and let ABS do the work more aggressively than I would've and instead put all my effort on controlling my near-spin... I might've been able to stop before hitting the tree. It was the scariest moment of my life actually, as my slide occurred on a long, lonely downhill on a mountain, with a big curve in the distance. Perhaps the hitting the tree -- with airbags -- was the better alternative to keeping things going but not under control for another 100 yards. When I imagine that situation, it makes me shudder.)

 

So the driver has time to look at the stupid readout on regen braking, yet don't have time to tell his brain to hit the brakes harder?!?

 

I notice it routinely with my Gen II Prius, but like any other driving characteristic, I compensate without even thinking about it. A very quick lift and reapplication of brake pressure drops ABS and puts the braking back into normal mode. I've never found it to be a problem.

Tom

 

^^ I've experienced this with my 2010 which I picked up about 2 weeks ago. It feels similar to when ABS engaged on my previous car hit a series of bumps causing ABS to think the car is sliding. A simple lift and reapplication of the brakes makes everything normal again. When this happened on my last car, the petal dropped to the floor so what's happening on the Gen3 isn't too bad.

 

Just curious, what was your last car?

 

^^ 2005 Scion tC lol

 

Would you call it a 'washboard' surface?

Is there a specific road where it happens or have there been four separate roads?

I'm having trouble finding a 'washboard' road to try and replicate this problem. I've never experienced it which is why I'm trying to find one.

Thanks,
Bob Wilson

 

For others who think this is just a Toyota problem, my 2001 and 2002 GMC trucks did something very similar when slowing down over railroad tracks or a bumpy surface....

 

lol

 

Any problems with 'tar-and-chip' road braking?

I'm not having much luck finding a road resurfacing project with a washboard surface. However, it looks like 'tar-and-chip' surfacing is common in some nearby counties. Has anyone had the 'brake problem' on these types of surfaces?

Thanks,
Bob Wilson

 

Regarding your comments about "wandering" at speed:

I appreciate your comments and have had the same experience with my 2010 Prius. My previous car was a bmw 232i. The Prius does not feel as rock steady in terms of keeping a straight line on the road at speed. I did improve this by switching my Good year Assurance tires for Michelin Primacy MXV4 (also the ride was not as harsh). The wandering problem improved but did persist.

Since you are experienced in racing I would like your opinion on a fix for this. I remember from my very brief racing days that reducing the tire pressure in the front relative to the rear promotes understeer (and straight line tracking) and increasing the fronts relative to the rear results in oversteer. Is this true in your experience? I tried this out by inflating the fronts to 34 and the rears to 36. It did seem after this that the car did track a little better and it was more predictable in moderately fast cornering. I realize that this could hurt my gas mileage.

A friend also suggested that the toe in on the wheel alignment be increased as small amount which could help tracking at speed. Any comments on this?