Sudden slow down braking system behavior

[vicpick58]

Great informative thread here! Really never put too much thought into this feature prior to reading this, but I sure will go test it out now for the sake of curiosity.



I wonder, could it possibly be the transmission downshifting rapidly and causing the vehicle to feel like it's still on the brakes a bit?

I've really never paid attention to my engine RPMs during a panic stop because well...I was too busy panicing

When I first got my 4Runner the brakes were the hardest thing for me to get used to, the panic or semi-panic slow downs were very scary.

I too experienced what felt like a lag from the time my foot backed off the pedal and the brakes actually releasing. I concluded after thinking about it for a while that the transmission must have been in the process of downshifting at the moment that I was pulling my foot off the brake pedal.

It probably took me a couple months to get used to these "touchy" brakes, but they sure do stop the vehicle fast when needed.

I have also noticed that if I pump the pedal once, the brake force ratio increases and less foot pressure is required.

As for anti lock brakes, I have never gotten used to them, my last few vehicles have had them and I still have a hell of a time slowing down in snow or gravel. I still like to lock em up for a second or two to dig in and build up that ridge in front of the tires. I don't like it when the pedal just buzzes and the vehicle keeps going past the point where I was expecting to stop.

 

[Bitsphere]

Intermittent braking (pulse braking) when you have ABS will guarantee you longer stopping distances and less control. Hit the brake, let the ABS do it's job and steer. You can steer with ABS with brakes to the floor. You are doing exactly the opposite of what you are supposed to do. Read up please.

[MENTION=66316]1engineer[/MENTION], this is precisely what I am referring to, is to be able to slow down at a longer distance. In this case I am referring to past experience with my Audi, to avoid sudden lock up and slippage on wet and bumpy intersections. But, you are correct otherwise, if it is an emergency, I would let the car handle the stoppage.

 

[Bitsphere]

A thorough thread but this part is left hanging a little bit.



I've never heard any reports of this behavior before, but it does raise the interesting question of whether it's possible that the force could persist noticeably if someone happens to release the brakes just as quickly as they got on them.

How certain are you that you experienced a release lag? Sounds like you have some experimenting to do for your own peace of mind.

[MENTION=2798]JB.[/MENTION]; I agree, I need to verify this.
In my last 28 years of driving, I could tell when my car decides to be the driver instead of being driven
Having said that, I am all for extra safety features on the road. Driving culture is getting nastier every year.

 

[Bitsphere]

Great informative thread here! Really never put too much thought into this feature prior to reading this, but I sure will go test it out now for the sake of curiosity.



I wonder, could it possibly be the transmission downshifting rapidly and causing the vehicle to feel like it's still on the brakes a bit?

I've really never paid attention to my engine RPMs during a panic stop because well...I was too busy panicing

[MENTION=85512]eddiebx[/MENTION] ; wow, this never occurred to me, and quite possibly it is, since the sensation of a sustained braking post releasing the pedal was very evident. Which means engine is participating in the braking system too !!

The RPM has another oddity which I am investigating now, and will report later. Variable rpm occurs while brakes are engaged at neutral gear at red lights, and rpm starts fluctuating every 3-5 seconds about 500 above 1000

 

[westwind77]

I wonder, could it possibly be the transmission downshifting rapidly and causing the vehicle to feel like it's still on the brakes a bit?

I too experienced what felt like a lag from the time my foot backed off the pedal and the brakes actually releasing. I concluded after thinking about it for a while that the transmission must have been in the process of downshifting at the moment that I was pulling my foot off the brake pedal.

There are quite a few threads on BA (Brake Assist) on this 5th gen forum, mainly people complaining about it. My BA actives weekly with my 'driving style', usually I curse it, but then again my 4R is telling me to stop driving like an a$$ (kind of like when the VSC beeps at you). Yes, there is a delay (as least to me) when you start to back off the brakes before the BA really stops doing its thing, but I have a feeling that is all software related and nothing to do with transmission downshift. As far as the computer is concerned you are in a 'panic' situation, it is going to push them to the floor, even if you release a bit it still does not know the situation has past so it will continue to do its job until some setting says it is safe (I would guess a full complete release of the brake pedal maybe?) You can hear and feel the BA system in effect even when you back off the brakes a bit, nothing to do with the transmission downshifting. I have never read anywhere about the transmission downshifting to help slow the vehicle also, and I have never seen my RPM's spike when my BA kicks in. If the BA system also had control of the transmission, and in order for it to be effective it really would have to drop and spike the RPM's to almost redline to be of any help. From my annoyingly frequent visitation with BA it does not control the transmission, just the brakes. I have a feeling if it had control of other systems in the 4R they would come up with some other fancy name to help market it.

 

[vicpick58]

There are quite a few threads on BA (Brake Assist) on this 5th gen forum, mainly people complaining about it. My BA actives weekly with my 'driving style', usually I curse it, but then again my 4R is telling me to stop driving like an a$$ (kind of like when the VSC beeps at you). Yes, there is a delay (as least to me) when you start to back off the brakes before the BA really stops doing its thing, but I have a feeling that is all software related and nothing to do with transmission downshift. As far as the computer is concerned you are in a 'panic' situation, it is going to push them to the floor, even if you release a bit it still does not know the situation has past so it will continue to do its job until some setting says it is safe (I would guess a full complete release of the brake pedal maybe?) You can hear and feel the BA system in effect even when you back off the brakes a bit, nothing to do with the transmission downshifting. I have never read anywhere about the transmission downshifting to help slow the vehicle also, and I have never seen my RPM's spike when my BA kicks in. If the BA system also had control of the transmission, and in order for it to be effective it really would have to drop and spike the RPM's to almost redline to be of any help. From my annoyingly frequent visitation with BA it does not control the transmission, just the brakes. I have a feeling if it had control of other systems in the 4R they would come up with some other fancy name to help market it.

Interesting observation, you may very well be right.

 

[thejuice]

Today I had my first encounter with the 'panic brakes' and I damn near hit a telephone pole.

Here was the scenario... I was driving home from work on the back roads of MA. The roads are windy, narrow, no curbs or barriers, and telephone poles stick out of the ground right where the pavement ends. Trees and hills block visibility around the bends, so you really only see the road from one bend to the next. I'm coming around a bend and spot an ambulance about 600 yards away. My speed was 40mph on the dot (a few seconds prior I looked at the dash). I had no intention or need to stop quickly, but wanted to get the pads on the rotors in case I needed to stop fast. I had really only pushed the brake pedal about enough of the way down to keep the car from moving forward from a stop light, but I guess I had tapped the pedal with enough velocity that 'panic mode' set in. The truck immediately nose dived, and just my luck, my outside front wheel dropped into a pot hole, and I lost the turn. My tires were squealing like crazy, ABS pumping, and the truck was creeping to the outside of the turn putting me in the path of the telephone pole. I guess it took a second but I realized what was happening and I took my foot completely off the brake, regaining enough traction to ride out the rest of the turn and clear the pole just inches from my mirror. I don't remember the next 30 seconds other than my hands shaking.

Meanwhile, I bet the ambulance driver was looking at the nose-diving SUV and thinking "WTF is that clown doing?!" My passenger screamed a lot of expletives that amounted to the same message, "why the f--- did you just floor the brakes?!", something about not getting into a car with me again, followed by some more expletives.

Wow, if there was one system I could permanently unplug it's this one. Thank you 4R forum!!! - it could have ended differently if I hadn't read about this nanny system. I'm going to try it out again in a controlled environment, and I think everyone else should feel it once before the 'feature' catches you by surprise!

 

[1engineer]

First timewas like that for me too. I know what to expect now so its no big deal. It will stop you RIGHT. NOW.

 

[harper7]

Today I had my first encounter with the 'panic brakes' and I damn near hit a telephone pole.

Here was the scenario... I was driving home from work on the back roads of MA. The roads are windy, narrow, no curbs or barriers, and telephone poles stick out of the ground right where the pavement ends. Trees and hills block visibility around the bends, so you really only see the road from one bend to the next. I'm coming around a bend and spot an ambulance about 600 yards away. My speed was 40mph on the dot (a few seconds prior I looked at the dash). I had no intention or need to stop quickly, but wanted to get the pads on the rotors in case I needed to stop fast. I had really only pushed the brake pedal about enough of the way down to keep the car from moving forward from a stop light, but I guess I had tapped the pedal with enough velocity that 'panic mode' set in. The truck immediately nose dived, and just my luck, my outside front wheel dropped into a pot hole, and I lost the turn. My tires were squealing like crazy, ABS pumping, and the truck was creeping to the outside of the turn putting me in the path of the telephone pole. I guess it took a second but I realized what was happening and I took my foot completely off the brake, regaining enough traction to ride out the rest of the turn and clear the pole just inches from my mirror. I don't remember the next 30 seconds other than my hands shaking.

Meanwhile, I bet the ambulance driver was looking at the nose-diving SUV and thinking "WTF is that clown doing?!" My passenger screamed a lot of expletives that amounted to the same message, "why the f--- did you just floor the brakes?!", something about not getting into a car with me again, followed by some more expletives.

Wow, if there was one system I could permanently unplug it's this one. Thank you 4R forum!!! - it could have ended differently if I hadn't read about this nanny system. I'm going to try it out again in a controlled environment, and I think everyone else should feel it once before the 'feature' catches you by surprise!

I believe it also has something to do with how fast your foot goes from gas to brake to how much braking action it gives. I've only had it happen twice in the 7 years I've owned a 4Runner and both times saved me and stopped straight and true.

Once in my 4th Gen from rear ending the guy in front of me when everybody in front of me locked them up on a on ramp due to a wreck . The guy behind me skidded past me on the right.lol And once 2 years ago in my 5th when a deer was standing in the middle of the road at night going 75 mph.

 

[1000MPH]

Yep, quick transfer from gas to brake will do it.
I recommend everyone that hasn't experienced it to go outside and give it a shot. You don't have to go that fast, maybe as low as 10-20mph.
Don't take Fido.

 

[philsey]

Don't take Fido.

ound:
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Maybe not the wife either. Mine didn't care for this feature when it happened to me on a bridge. Me, I'm very impressed by this truck's brea..... er brakes.

 

[westwind77]

I believe it also has something to do with how fast your foot goes from gas to brake

:thumb::thumb: From all the digging that is one of the parameters it (the computer) uses to determine if the BA system should initiate. The speed it which you go from the gas to brake, then the force applied to the brake. The system is easy/simple to trip. If you do a hard acceleration then midway quickly tap the brake with a little force hang on, lol. We have bike crossings ALL OVER where I live. They are suppose to stop, then walk the bike across, but some of the (insert many curse words) people blindly pedal across, assuming the 45mph vehicle will stop in 25 feet. BA is used more than my wipers!