optionpunk

My 2010 RX 450H has a serious braking issue. The following is a post from a UK site that details my problem exactly:

"Over bumpy surfaces (i.e. most of the uk) and when turning into corners, the brake system automatically releases braking pressure (causing the driver to sense a relative surge of acceleration), and then automatically re-applied brake pressure – with no change in input by the driver."

I have spoken with Lexus Canada and have had the car in for an inspection. After the inspection was done the dealer confirmed that they had experienced the problem as detailed above during the test drive however when the final report of the inspection came from Lexus Canada they denied that there was an issue. Possible that this was a miscommunication but it has not reinforced my trust in the brand. Considering that Lexus has had hybrid braking issues for other models I'm wondering if anyone else has experienced anything similar? Thanks.

BertL

Welcome to CL, your first post, and owning a 2010 RXh.

I have not experienced any issues like this on my former 2006 RX400h I took delivery of in 2005 or my 2013 RX450h that replaced it nearly 18 months ago.

optionpunk

Thanks BertL. The other poster who had the issue began to experience it at approx 45,000 KM and my issue began at around 55,000 km. Hopefully it doesn't occur with your vehicle.

DunWkg

We have discussed this issue with the 2010 models a long while ago. I honestly don't remember if any of us had anything done to correct it. However I think the problem is gone in the 2012 and newer models.

Driving over a section of "washboard" road and braking at the same time, the issue is very pronounced. An issue with the ABS as I recall. I don't remember the quirk rearing it's head while cornering, but my memory is faulty.....

Droid13

This has been an ongoing complaint across all Toyota hybrids for a number of years. On my 07 Camry Hybrid this was quite noticeable on bumpy roads or paved roads covered with some dirt when coming to a stop, especially when the tires started to get old and no longer had optimum traction, or before I had put the snow tires on and the roads were very cold. If you're the type of driver that leaves no room/time to spare when breaking, yea, you're likely sooner or later to ding a bumper. If you leave a few ft of safety margin, it can be a little bit of adrenaline surge on occasion. This issue is related to the dance between ABS and regenerative braking. While the tires begin to lose traction the ABS signals the regenerative braking to ease off and mechanical breaking to take more priority. If traction drops quickly (hitting bumps, dirt) there is sometimes a momentary lag between the two, giving the feeling described. It may feel like the car speeds up, but it actually just doesn't slow down as fast as it was slowing down for a moment.

My 2010 RXh is so, so much better I barely notice it. When it does happen, I think I only recognize it because it was so noticeable in the Camry, and if it wasn't for the Camry I'm not sure I would notice at all.

Now with all that I know about this topic, the suggestion I have is take a hard look at your tires. You say it started at 55K, well, if you have original tires that are now 4 yrs old, that's probably your problem, the braking traction is much lower so the issue is becoming more pronounced. Doesn't matter if you have tread remaining, 4 yr old tires simply don't cut it. That's where I would look first. If you've recently had new tires put on, post the brand under the banner "don't buy these, they suck" :-)

BertL

Andy, a very informative response. Thanks -- I learned a couple of things. ...and no wonder I have never noticed an inkling of this sort of situation if my RX even had/have them, living life in Southern California with too many potholes, but otherwise decent roads compared to many other places, and not much to worry with slippery-road-wise since it almost never rains (or snows) in California where I am. Always good tires and my tendency to not wait until the last moment to brake probably help as well. Thx again.

kitlz

It's happened a handful of times to me but on straight roads. It wasn't enough for me to mention to the dealer since it's been pretty infrequent over almost four years of driving the 450h. And unfortunately I can't recall if it was before or after I changed the tires. Thanks for the info, Andy. I'll ask my SA next month when I'm in for the 30K service. If she doesn't know, she'll ask someone else that might.

DunWkg

Andy, As I said my memory is faulty, but I seem to remember recognizing the anomaly early in RX ownership. Implying it wasn't a tire condition problem for me. Lunging forward as I pulled up behind another car at a stop light on a pot holed street surprised me first time it happened.

Your point of it not being noticeable until some tire wear occurs is an interesting observation and may be an important safety issue for RX owners need to take into consideration. Thank you for your explanation.

CometVR4

I've experienced this on our 450h as well. I figured it had something to do with ABS.

I had an Acura TL that would almost always engage ABS if I'm braking over rough pavement enough for braking power to be reduced for a second.

fastnoypi

Is this issue only experienced in hybrids? My 02 subaru wrx had this issue as well. It was an over sensitive ABS system. The solution was a ABS module reprogramming.
Im guessing Toyota/Lexus have a similar solution.

Cruiter

Andy, Like Bert said, very well written. It's actually more understandable than Toyota's and Lexus's explanation. We live in a hilly area and there's a particular left turn I make when going into another neighborhood. I usually have to slow down a lot as it's more than a 90 degree turn and downhill with rough pavement. Almost every time I take it if I'm at 15mph or greater I'll get the same effect. It's just knowing the car and when to expect it and how to handle it.

I'd define it more as a characteristic than a defect. All the little computers are trying to interpret input and correct output.

DunWkg

This lengthy and older discussion was held among some Chevy Volt owners. The one comment that seemed to ring true to me was, "lack of deceleration feels like acceleration". The mind plays a part in perception versus reality.

The discussion may not be relative to ours, but here it is:
http://gm-volt.com/forum/archive/index.php/t-14808.html

vlad_a

My Prius did the same thing. As Andy has pointed out, it works as designed. Just keep the pressure on the brake pedal. The vehicle is not accelerating, even if it feels like it does.
I think FWD version will have a more pronounced effect due to only 2 wheels being used for regen.

kitlz

Very interesting posts from everyone who's experienced this issue in other vehicles. So we can surmise the RXh is actually slowing down instead of speeding up as well. I'm almost tempted to record the data and check for myself.

optionpunk

Andy your response has helped me put some of the pieces together in this puzzle. I recently had my tires rotated and the fresher rears moved to the front and noticed a decline in the frequency of this occurrence. That also brings up some obvious issues with the first being that the older your tires get and the less traction you have the more likely you are to have your brakes momentarily release on you. the compounding effect of less traction coupled with a momentary loss in braking is a huge issue. It's also problematic for those of us who live in snowy climates as we are pretty much guaranteed to lose braking under normal winter conditions. Putting some numbers behind this - if I'm travelling at 50kmh (typical city driving speed) at the time my brakes release and they release for 1/2 second my car will have travelled 22.78 feet in that 1/2 second. I firmly believe that the brakes 100% release as I don't think that I would be fooled into thinking the car accelerated for a lesser percentage. But even if you applied a % to the 22.78 feet you still have your car stopping slower than you expect and that's simply dangerous. I suppose if all of the cars do it it could be framed as a characteristic of the car and maybe/maybe not a defect but it's definitely a dangerous design flaw. Is there any other way to consider a design that would have your brakes release under braking with no input from the driver?