Car Lunge Forward While Braking Over A Bump

[400h08]

This has been discussed many times before, and I haved asked my dealer about it, but their answer was they could not find anything wrong. But now, Prius owners are making the same complaint, and Toyota is investigating. Does it mean Lexus owners are second class citizens (or owners)?

http://www.bnn.ca/news/15500.html

Toyota quality woes hit Prius hybrid

Reuters

February 03, 2010

Toyota Motor Corp. said on Wednesday its North American and Japanese dealers had received several dozen complaints concerning what drivers characterized as insufficient braking on its new Prius hybrid car when driving over bumpy or frozen roads.

Toyota received the first reports of the Prius complaints last December, a spokeswoman in Tokyo said, adding that it was investigating the issue. She said there had been no reports to Toyota about any accidents related to the matter.

The third-generation Prius has become a core volume-seller for the world's biggest automaker, and is now Japan's top-selling model. Including second-generation models, Toyota sold 404,000 Prius cars globally last year.

In Europe, where the automaker has sold 29,000 new generation Prius cars since its launch last summer, Toyota Motor Europe has not had any complaints, a spokeswoman for Toyota Motor Europe said.

[rcomeau]

This has been discussed many times before, and I haved asked my dealer about it, but their answer was they could not find anything wrong. But now, Prius owners are making the same complaint, and Toyota is investigating. Does it mean Lexus owners are second class citizens (or owners)?

I have not reviewed the posts, but when you hit a big enough bump while breaking, the anti-lock system may interpret that as a wheel slip, and release the brakes a bit (that's what anti-locks are for). Since you are in a braking condition, you are feeling deceleration, and the release of the brake feels like an acceleration when it is really a decrease in the deceleration. This is analogous to getting on a broken escalator. In that first step, your brain expects your body to accelerate and automatically compensates which makes you feel strange for a split second since you don't actually accelerate.

This is assuming what you felt was a momentary sense of acceleration at the bump, and then the braking felt correct after.

I hope this helps.

[lemon]

This is a hybrid problem only. From what I understand, it's the regenerative braking being completely disabled and the regular hydraulic/caliper brakes being completely enabled to provide ABS. As stated above, it's not an acceleration, so much as it is a decrease in deceleration. Perhaps there's a split second where neither system is braking? I've experienced it the odd time on my 400h, but it didn't cause me to rear end anyone - in fact I ended up pressing the brake pedal harder and stopping more abruptly when the hydraulic system kicked in. I suppose a less experienced driver might actually let up off the brake pedal in surprise, thinking something was wrong and thus hit something??

[RX400h]

That's a good analogy, RC,

We have recently discussed this:

http://us.lexusownersclub.com/forums/index...showtopic=62220

[400h08]

Yes, these are the perfect explanations. But, it does not solve the problem. No other cars behave like that. If I do not want this kind of behavior, do I have to abandon buying hybrids? I think it is a design fault. Hopefully, with more complaints from Prius owners, Toyota will come up with a fix.

[RX400h]

Personally, I think the complaint by Prius owners of "insufficient braking" is highly exaggerated. It is a quirk of the regenerative braking system, but as was mentioned, is not a safety issue unless many accidents are being reported.

I remember having a loaner Nissan Maxima in 2005. The throttle was touchier than what I was used to and for a brief while, it was disconcerting. Was it a safety issue that should have resulted in a recall? No, but it was different than the "norm" and thus was subject to customer complaints.

[LexRexBlue]

I've complained about this since the first year. They do have that explanation but no solution. The worst is hitting a pothole at the bottom of a hill with a Stop Sign and you can't stop. However, dare I say you get used to it and brake in advance! The only scary time is during snow/sleet because then you have less control afterwards.

I don't think we're second class citizens but they didn't make as many RX hybrids as Priuses. It's numbers and Toyota is generally under closer scrutiny. I'm going to wait and see what they come up with because if its what has been going on in the RX400h since 2005 think about how many cars it must affect.

[400h08]

I've complained about this since the first year. They do have that explanation but no solution. The worst is hitting a pothole at the bottom of a hill with a Stop Sign and you can't stop. However, dare I say you get used to it and brake in advance! The only scary time is during snow/sleet because then you have less control afterwards.

I don't think we're second class citizens but they didn't make as many RX hybrids as Priuses. It's numbers and Toyota is generally under closer scrutiny. I'm going to wait and see what they come up with because if its what has been going on in the RX400h since 2005 think about how many cars it must affect.

Well, it is in the news again, and quite confusng and conflicting news:

A Toyota spokeswoman said there was no decision yet on whether to recall the Prius but said the company is investigating possible brake problems with its luxury Lexus hybrid, which uses the same brake system as the Prius. Toyota has not received any complaints about the Lexus HS250h and the probe is to ensure safety, spokeswoman Ririko Takeuchi said.

Quoted from this article:

http://ca.news.yahoo.com/s/capress/100204/...s_toyota_recall

But, it did not mention RX400h or Rx450h, only HS250h.

[riwyle]

Maybe Henry Ford was right. He insisted on using mechanical brakes on all of his cars until, I believe, 1939. His slogan was, "There must be metal from the pedal to the wheel". (although some say he just didn't want to pay Bendix who held the patent on hydraulic brakes). Many manufacturers continued to have mechanical backup in case the hydraulic failed.

What would Henry say today if he saw what is between the "pedal and the wheel" on our hybrid cars? I believe he would be turning over in his grave.

It seems like the philosophy today is, why have a simple mechanical system when it can be replaced by a complex, electronic, computer operated, system.

[RX400h]

Well, I guess we can say the same thing about carburators, ignition points, drum brakes, roll-down windows, no air bags, manual steering, and hand-crank starters.

Nah, I'll take at least some of the modern stuff, thank you!

[Jim Clark]

Well, I guess we can say the same thing about carburators, ignition points, drum brakes, roll-down windows, no air bags, manual steering, and hand-crank starters.

Nah, I'll take at least some of the modern stuff, thank you!

LOL! Our cars have become much more complex as each decade has passed, especially in the last three with the advent of computer controlled everything. But they've also become much safer. When Tucker was an advocate of seat belts in every car, pop-out windshields, and other safety features, he was considered a nut and the big three fought all of it. They still fight gas mileage and emissions requirements. Yes, they have their hybrids now. Why? Because Toyota led the way and they had to do it to compete. You can forget about trying to sell a car today without a FULL complement of airbags, ABS, traction control, etc, etc, etc.

Our 2010 Prius bought in the C4C program doesn't have memory seats, mirrors, and steering wheel like the RX400h. It's quite an inconvenience. But, it does get 50 mpg which is nice.

[chand3]

With all this news on a recall for the Prius, it's probably just time before there's one for our RX. My concern is whether or not this fix will affect fuel economy. If reprogramming is just making use of the hydraulic brakes more and less for the generator, then I'd think we'd ultimately lose efficiency.

[RX400h]

Yes, if percentage hydraulic braking vs. regenerative braking increases, we'll all be replacing our brake pads far sooner. What will probably happen is that a more complicated system will be developed to know ahead of time when rough roads/no propulsion conditions are immenent. Regerative braking will be disabled and the former non-adjusters will be happy.

[Jim Clark]

Yes, if percentage hydraulic braking vs. regenerative braking increases, we'll all be replacing our brake pads far sooner. What will probably happen is that a more complicated system will be developed to know ahead of time when rough roads/no propulsion conditions are immenent. Regerative braking will be disabled and the former non-adjusters will be happy.

LOL RX!

[RX400h]

Yes, if percentage hydraulic braking vs. regenerative braking increases, we'll all be replacing our brake pads far sooner. What will probably happen is that a more complicated system will be developed to know ahead of time when rough roads/no propulsion conditions are immenent. Regerative braking will be disabled and the former non-adjusters will be happy.

LOL RX!

Hey, it's good to laugh during these "trying" times........ :)