NHTSA Tracking Braking Loss on Prius Hybrids

I don't believe anyone is second guessing the dual owners. Let's say we accept their posts as being factual. In that case we have some evidence supporting the claim that the issue exists in both the Gen II and Gen III. What we can't deduce from a small number of reports is whether the issue is perceived to happen more often in Gen III Prius. No speculation is necessary, only logic and statistical significance.

We shouldn't be quick to eliminate the possibility that some difference exists between the Gen II and Gen III. We know that most of the Prius was re-engineered for the Gen III, so it is entirely possible that they could behave differently. I'm not saying that they do behave differently, or that we have evidence to that effect. All I am saying is that a very real possibility exists that the Gen III is somehow contributing to this perceived problem.

Until we have more data it would be irresponsible to assume that the Gen II and Gen III behave in exactly the same fashion. It could be the cars. It could be the owners. It could be something else. It could be nothing.

Tom

 

Just some anecdotal evidence for everyone. My drive to work takes the same route every day. Along that route is a section of road that has a number of potholes created by old man winter. I took this same route with my G2 as I do presently with my G3. While I learned to avoid most of the potholes on this section of road, occasionally I would not be on my 'A' game and I would hit one or two of them. The reason why this section of road is important is because I have slow down to make a right hand turn where most of the potholes are so I apply the brakes. In both the G2 and the G3 I would lose breaking force for a fraction of a second immediately after hitting a pothole. Symptomatically there is no difference. I do not know what differences between the vehicles exist from a mechanical or software perspective though I am sure there are many. Thus I am in no position to conclude anything other than what I have observed as a Prius owner. I will say that I am not overly concerned about it. I know what "causes" the issue to occur and given that I don't make a goal out of hitting potholes, it is relatively easy to avoid the issue altogether. Hopefully Toyota at a minimum investigates the issue. While I am not bothered by it, there may be some owners that are.

 

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As I said in my prior post (but you left off) -

"To be clear, I am NOT precluding that there may be differences, but without additional supporting information, what point does it serve to further cloud the issue with pure speculation?"

I stand by this statement. IMO, speculating without facts/supporting information just serves to fan the fire of hysteria.

 

Can you provide Google or Google Street or photos of specific locations where the problem occurs? I'm trying to collect these locations to see what is common:

http://hiwaay.net/~bzwilson/prius/Prius_bump_010.jpg
http://hiwaay.net/~bzwilson/prius/Prius_bump_020.jpg
http://hiwaay.net/~bzwilson/prius/Prius_bump_030.jpg
http://hiwaay.net/~bzwilson/prius/Prius_bump_040.jpg
http://hiwaay.net/~bzwilson/prius/Prius_bump_050.jpg
http://hiwaay.net/~bzwilson/prius/Prius_bump_060.jpg
http://hiwaay.net/~bzwilson/prius/Prius_bump_070.jpg
http://hiwaay.net/~bzwilson/prius/Prius_bump_080.jpg
http://hiwaay.net/~bzwilson/prius/Prius_bump_090.jpg
http://hiwaay.net/~bzwilson/prius/Prius_bump_100.jpg
http://hiwaay.net/~bzwilson/prius/Prius_bump_110.jpg
http://hiwaay.net/~bzwilson/prius/Prius_bump_120.jpg
http://hiwaay.net/~bzwilson/prius/Prius_bump_130.jpg
http://hiwaay.net/~bzwilson/prius/Prius_bump_140.jpg
http://hiwaay.net/~bzwilson/prius/Prius_bump_150.jpg
http://hiwaay.net/~bzwilson/prius/Prius_bump_160.jpg

Bob Wilson

 

Speculation is how humans play "what if" games. Without speculation and conjecture there is no scientific process. First we say "what if..." and then we find a method to test the speculation.

You are taking the role of the wet blanket, greeting each new suggestion with the standard "that's a stupid idea" comment. This sort of behavior is common in brainstorming sessions, and it's not helpful. The beginning stages of problem solving are data collection and the generation of theories, also called speculation.

As for "pure speculation", sure, there is some of that. It's generally not helpful, but neither is your dogmatic stand against anything not supporting your one and only party line. Allow people a little room to breath. Some of this wild speculation may lead to creative ideas.

Tom

 

This is the intersection with three sets of speed bumps

Google Maps


This area (coming down the hill to the entrance of Rt 19) is smooth, yet as the car decelerates, with no bumps, it and my HH has given the brief sensation of "letting go".

Google Maps


I know the sensation is worse than the actual event, but I can see how it scares some. I try not to tailgate so the rumble strip area (first picture, about where the truck is located approachint the T intersection) is an avoidable situation. Sure if bumps were in other places it might happen and be more of a concern, again only if I were tailgating.

In the second picture, there is actually another curve just above the intersection where I have had the same sensation as ayt this intersection. BOTH are on a mild slope downhill while making a 90 degree turn. Obviously at the intersection I am stopping, where as at the curve above I am merely slowing. It's not consistant as I am always doing a different speed and at times, when it's just right, it occurs. In the slowing down at the curve, the first time I merely had to turn faster than I thought I needed as the vehicle felt like it was heading to the guardrail. At the intersection I am more careful now as I come to a stop well before the edge of the road and then creep up.

My situations are more than just potholes and with a little effort are probably more easily repeatable (especially since no one wants to experiment by hitting potholes intentionally). However it has always been my goal "not" to repeat them. However with these pictures you might be able to find a similar situation in your area to experiment with.
I love my HH, I like my Prius.

 

This might have already been covered, but when the vehicle "lets go" would you say that was the regenerative breaking releasing? What does the HSI show (e.g. regen of some value to 0 when "letting go")?
If this is happening, I can totally understand feeling the sensation.

 

My experience with the Gen II shows regen being completely canceled. To restart regenerative braking, I have to pull my foot off of the brake and then reapply pressure. If I simply keep braking I get friction braking only.

Tom

 

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Yeah, don't put yourself in danger... it would be nice if there was a trace/history thing in ScanGuage to measure this.
One thing I want to clarify, are you just coasting or do you actualy have the brakes applied when you feel this "letting go"?

 

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I've only noticed the ABS light kicked on and the brakes respond accordingly so on certain bumps when driving slower.

NOW, one thing that I have noticed is when I have my cruise control set, then I apply the brakes I fell a sudden 'acceleration' type feel, which doesn't register any change in MPH(speed) on the LED display, but I've grown accustomed to this, I figured it was common with the regenerative braking system. It's not like I hit the brakes and suddenly my explosive 4 cyl. engine roast the tires and I suddenly jolt to 100+ mph LOL!

I will test the brakes on some bumps, but usually if you were to brake on bumps going on the interstate it wouldn't matter 65mph+ LoL, or in town driving 30mph or slower. And you shouldn't ride all over peoples butts in town anywas in any vehicle. So I think it this becomes an issue, they should just tell people to be more cautious while driving in town. Prius are not made to fly around town hitting bumps and braking like mad to avoid hitting people.

 

I've seen this 3 or 4 times in 7000 miles. Always when I hit a large bump in the road, the car 'surges'.

 

This is the bump i've had it twice on (2 blocks from work)

11382 ostego st north hollywood, ca 91601 - Google Maps

 

With brakes applied, right?

 

I believe that the problem? with the brakes is due to the regenerative braking, which only acts on the front wheels.
It goes like this. The car is slowing using a combination of the regenerative braking and the hydraulic brakes. The car encounters a loss of surface traction. A disproportionate amount of the braking is being provided by the regenerative brake system at the front wheels. The car losing its traction with the road surface is perceived to accelerate. The driver pushes the brake pedal harder. The hydraulic brakes provide the stopping power the car stops normally.
This situation does not occur in a non hybrid car because all 4 wheels are contributing to the braking force at any given time. Unless as those who live where I do the roads are often covered with ice.

The fix would be to set the hydraulic brakes to act sooner to lessen the time between when the regenerative braking is doing most of the work and when the hydraulic brakes take over the job. The problem is this will reduce the efficiency of the regenerative braking system.

I do not believe it is a problem, Yes I have felt this anomaly, but I believe it is manageable. By the way it has nothing to do with the anti lock brake system.

Be aware of your driving situation, slow down, don't allow a bunch of nanny bureaucrats dilute the efficiency of a finely crafted piece of machinery.

 

Four more images:
http://hiwaay.net/~bzwilson/prius/Prius_bump_170.jpg
http://hiwaay.net/~bzwilson/prius/Prius_bump_180.jpg
http://hiwaay.net/~bzwilson/prius/Prius_bump_190.jpg
http://hiwaay.net/~bzwilson/prius/Prius_bump_200.jpg

Thanks!
Bob Wilson

 

Japan Orders Toyota to Investigate Complaints Over Prius Brakes - NYTimes.com

"A Toyota spokesman, Takanori Yokoi, said dealers in North America and Japan had received “several tens” of reports from customers who said their Priuses had “braked insufficiently” on bumpy or frozen roads."