brake surge again!

I have experienced similar "surges" on my 2010. I did not notice any problem with the brakes until the dealer updated the firmware... I don't recall ever having that occur on my 2004 Prius. I wonder if there is a way to check the firmware version (although since you have a 2011, the brake firmware update TSB was long past).

 

We have never experienced this.

 

Can you reproduce this at will?

Bob Wilson

 

I can make the apparent loss of braking appear on demand at certain rough or graveled intersections. I can also usually avoid it altogether by leaving more following distance and braking gently to take better advantage of the regen capabilities. If I unexpectedly encounter an occurrence, I've learned to mash down on the brake pedal to engage the friction brakes. I had that happen today when going over wet railroad tracks.

Every car I've ever owned has had its share of quirks that I've learned to live with - from cold start knock in past GM trucks to my current Lexus GS that shuts the radio off when it gets confused talking to my iPod.

 

Isn't it loss of regenerative braking, rather than loss of friction braking. Push a little harder on the
middle pedal when you need to stop faster.

 

I thought the Prius turns off the regen braking when a bump generates unpredictable currents via the regen system that could potentially hurt the battery and electrical system. But then I looked up braking threads in the Gen III forums and found this good explanation:

From this thread; So the brake surge is still there, despite recall | PriusChat

I can watch the friction brakes kick in on my ScanGauge II when I'm braking and hit the familiar local bumps.

Curiously, on my 2012 Prius v (wagon) w/ATP, when I see the friction brakes activate on my ScanGauge II and press harder on the brake pedal (presumably) because of the loss of regen braking, then I still see the Hybrid System Indicator white bars in the charge area. What is up with that?

 

There is no way to quantify "rough or graveled intersections." I am interested in the braking problem on paved roads with or without a pot hole. But the pebbles or stones of a graveled intersection could have more in common with a bed of ball bearings. I'm sympathetic but there is nothing to be done about such surfaces.

Bob Wilson

 

I don't buy it.

I used my brakes so much and so often that I need to replace them every 30,000 miles and since the recall update I have NEVER had the brake 'issue' since. Sometimes you do get the ABS kick in in the same way it would/does on any other car, but the braking on the gen3 Prius is fine in my significant experience of it.

My money is on someone trying to blame a car for their bad driving! Sorry.

 

Persistence is the 'tell' I look for. If the original poster moves on and won't support debug, there is nothing to be done but move on.

The original 'brake pause' was real and measurable ... I measured it. When the fix came out, I was able to confirm it fixed the problem. But with any intermittent problem there is always the possibility of a second, less frequent problem. The key is getting facts and data, quantifying what is going on.

I'll watch the thread for a couple more days but if the OP can't reproduce the problem or provide any additional facts and data, say an exact location of the incident, we'll just have to 'dust off our sandals' and move on.

Bob Wilson

 

I've had panic stops on bumpy roads in the Prius and, like every other car I've owned, I keep pressure on the brake pedal through the entire episode and the car stops. The first time was interesting, but after that I knew what to expect.

 

I've been driving rental Prii over 20k miles since mid 2009. I experienced the original delayed braking over bumps and later after the update, the neck snapping grabby brakes that all Prii have today, that have been updated or are current production cars including my own Prius. Even today's Prius brakes have a different feeling than a conventional car but they always stop the car no matter what road the car is on, smooth or potholed. I honestly preferred the brake action before the update, but you'd have to expect the delayed braking when on rough roads. Today's Prius braking is so touchy/grabby that it almost appears too aggressive, but it works. Does the car wear out the friction brakes sooner with the update?

Mike

 

I think it might do ever so slightly but have no proof other than a gut feeling.

The reason my brakes wear out so quick is a, the European brakes have softer pads and discs as apparantly we prefer our brakes to have a sharper 'feel' and b, I drove my car in start stop bumper to bumper traffic in a compact town where my average speed was often about 12 mph over a day and the streets are short and narrow - I was on my brakes more than off them!

 

Perfect! To diagnose this, we need two things:

• Exact location where this happens - with luck, we'll find someone else with a similar Prius to replicate the problem at that location. We need to know if this is unique to your car or common to all Prius or unique to just this location. Knowing the location and scenario is key. Once we see the details via Google Earth and the topology, we'll try to find a similar road in other areas. Photos of the street and any additional technical details will help. We can not rule out a defective road and this helps determine if the county/state road department has a problem.
• Accelerometer - I will loan you one of these to measure the G forces during these events: A record of the events allows us to quantify exactly what is happening. For example, the earlier brake pause: Notice how the blue dots went to zero for about 800 msec. This is the braking pause after an impulse at slow speed on a slippery surface that the patch fixed. But there could be a more subtle braking dynamic going on, one that is harder to replicate.

Send me a note with your mailing address and I'll loan you the accelerometer and instructions. The general scenario is: gently push the 'start' button with a pen or paper clip to start recording; tape it to the car and; note the time. Then drive normally and replicate the brake problem. Try to record the time when the problem occurred so we'll know where to find it in the data. When you get to a safe place, you can stop the data recording with a pen/paper clip which helps narrow the amount of data we need to look through. Then you can load the data and/or send it to me to analyze with a spreadsheet. We'll try to get at least three examples to help characterize the problem.

What we are doing is documenting the conditions that lead to the problem so others can try and replicate it. We're also quantifying, taking measurements, so we can share it with Toyota and later, verify the problem has been resolved.

Be open minded as we need to determine:

1. Unique to your particular car - this means something is broke and needs to be diagnosed and fixed.
2. Unique to that stretch of road - not only your car but others experience the same problem. This might get fixed by road work.

Please be patient as diagnosis of intermittent problems always takes longer than one might wish. However, this is an approach that has a high probability of success.

Bob Wilson

 

I have experienced this, but I have also experienced the same thing, on just about every other car with ABS and TC. I drive in very hilly terrain, with long lines of potholes that some refer to as roads. When travelling downhill at a fairly steep grade, and applying the brakes, if the car hits a large bump, pothole, patch of extremely rough road, or loose stones, the onboard computer senses the loss of traction and reduces or releases the brakes to allow the tires to re-grip the pavement. This is the definition of an “Antilock Braking System”. It was designed to prevent the wheels from locking, which turns braking into skidding. Skidding is an out of control condition, and therefore bad. The best way to deal with it is to not let it shock you; just keep firm pressure on the brake pedal and let the computer do its job. I see that the OP is a few years older than me, so I must assume that he, like me, learned to drive without all of the computer assisted braking and traction control systems. I still find that my internal braking and traction control system; i.e. my brain, sometimes tries to “feather the brakes”, as it was called back then; this only makes it worse. We simply must retrain ourselves to deal with the new technology. I am learning to keep steady and firm pressure on the brake pedal, and as long as I do this I have never had a vehicle go out of control. I admit that even though I have been driving with these more advanced systems for several years now, there are still times that it just feels wrong to keep pressing the brake pedal, and I have to struggle to override the old way I was taught to drive. Could the OP’s car have a problem? Sure, I suppose it could, but what he describes sounds like how every car with ABS and TC behaves in the conditions he specifies. I agree with GrumpyCabbie; the first time I test drove my 2012 Gen III, and used the brakes, I just about put myself through the windshield, they really grip. I would complain to the highway dept. and tell them to fix the unsafe road conditions on the roads his taxes pay for, if it were me.

 

It looks to be "300 E Market St., Orwigsburg, PA"

You're headed SouthWestSouth and make a right on to East Market St, near as I can tell. I assume it is the approach to the intersection that causes the grief.

If you get a chance, park and walk up the sidewalk and look at the water trail that goes to the drain. Pay particular attention to the section where the yellow paint ends. I can not tell for sure from the Google street view but it looks like about a 20" from the curb, the water has worn down the surface pavement and possibly exposed some of the rock agate. In particular, look to see if there are 'smooth stones' in that water track.

Please take a camera and see if you can take some close-up, in-focus shots of that part of the street. Without taking a risk, a photo close to the surface of the street both down and from the intersection up might also give more details about the road surface profile.

One other option is to mount the camera on a tripod and get as far away as maximum zoom will support. Then take a photo to see if there is a dip where the water may flow away from the curb.

It would be great if you could measure the slope. The white framed house suggests a pretty steep slope. We don't need exact but a reasonable metric.

Thanks,
Bob Wilson

 

I've certainly noticed the ABS light flashing when I am (lightly) breaking and hit a rough-but-paved patch. I've got a 2012 prius 4. I'm used to ABS systems, and assumed it was just extra touchy compared to my old car.