Sudden slow down braking system behavior

[Bitsphere]

Greetings,

While trying to understand what happened when I had to hit the brakes suddenly panicking over the sudden stop of traffic ahead, my 4Runner "SR5-013" decided to continue slowing rapidly and sustain a longer period for engaged brakes eventhough my foot left the brake pedal instantly. Almost got hit by the car behind me, as my brakes overdid it.
I tried to read about it, but no idea what this jargon means:

ABS
Brake assist system
Four-wheel disc brakes: four ventilated
Electronic brake distribution
Electronic traction control (via ABS & engine management)

My question is this: if I encounter a situation at a higher speed, how do I use these brakes?
So far being cautious, I press the pedal at a smooth accelerating pressure to slow it down without risking a full stop of the wheels, while accounting for road conditions too (i.e ice, snow, water). But, I am concerned of more serious situations, the brakes my overdo it.

Any tips would be really appreciated.

 

[4RBob]

I don't have any tips, but completely agree with you, 4Runner braking system overreacts.

 

[alc9020]

it is mother Toyota telling you, you need to stop.

 

[1engineer]

If you hit the brakes fast and hard, the 4Runner "decides" that you really want to slow down right now and assists you. Now I have used this feature before and it is a little un nerving but if you know what to expect it's fine and helpful. I will tell you though it does not keep braking longer than you intend. When you let off it lets off. The car behind you almost hit you because you slowed down quicker than them.

 

[Coveman]

I tried to read about it, but no idea what this jargon means:

ABS
Brake assist system
Four-wheel disc brakes: four ventilated
Electronic brake distribution
Electronic traction control (via ABS & engine management)

.

Lets take a stab at these terms...

-Antilock braking system- that pulses the brakes to avoid locked up wheels
-We have a hydro boost system that boosts the brake pedal force to the wheels
-Disk brakes on all four wheels, and ventilated for cooling
-The job of the EBD as a subsystem of the ABS system is to control the effective braking power by the rear wheels. (Most braking force is sent up front)
-Traction control will kick in automatically when your vehicle detects wheel spin, like in snow going up a hill, to brake the spinning wheel and reduce engine power.

Plus one more...
Electronic Stability Control that improves the vehicle's stability by detecting and reducing loss of traction (skidding). When ESC detects loss of steering control, it automatically applies the brakes to help "steer" the vehicle where the driver intends to go. Braking is automatically applied to wheels individually, such as the outer front wheel to counter oversteer or the inner rear wheel to counter understeer.

Helpful?

 

[westwind77]

Yes, it is 'normal' for the 4R, part of the safety system...

Technology File | TOYOTA MOTOR CORPORATION GLOBAL WEBSITE

I activate it a lot, not a fan of it, but I'm sure it will help me one day when I need it. Now it just seems to do the job of keeping my passenger seat free and clear of anything I leave on it.

 

[ant-ny]

yeah, it takes some getting used to. the few times i have really had to jam on the brakes, i felt like i may go through the front windshield! that being said, although it can be an unpleasant experience, i am very surprised how quickly this truck can come to a stop when you need to. the one time my wife was riding, i think she almost pissed herself!

and, if someone hits you from behind, it is their fault, no matter how fast you stopped.

 

[Bitsphere]

Many thanks for the information.
Now that hydro boost seems to be the primary culprit in this case. Why would Toyota think my leg is not up to the task?!
Looks like the auto industry is following the example of computer industry by presuming all drivers/users need assistance.
This feature could be dangerous for experienced drivers who are used to certain response from their vehicles.

-- edit: lol, there is hypocricy in my statement above, as I really love the rear view camera, and miss the auto feature for the lights and windshield wipers.

 

[Bay33saw]

When I bedded in my new brakes after purchasing my 12 LE (I have a motorcycle racing background and alway bed in my brakes on my bikes and cars...
http://zeckhausen.com/bedding_in_brakes.htm by Dave Zeckhausen

I too was like "Holy S**T" as my eyes were nearly sucked from my eye sockets on my first run due to the help the car gave me while braking. After a few runs I kind of got used to it, if I was you, I'd find a deserted road and so some runs like Dave Zeckhausen said above, not only will it bed in your brakes it will give you some practice on your brakes..

 

[1engineer]

Many thanks for the information.
Now that hydro boost seems to be the primary culprit in this case. Why would Toyota think my leg is not up to the task?!
Looks like the auto industry is following the example of computer industry by presuming all drivers/users need assistance.
This feature could be dangerous for experienced drivers who are used to certain response from their vehicles.

-- edit: lol, there is hypocricy in my statement above, as I really love the rear view camera, and miss the auto feature for the lights and windshield wipers.

I am a very experienced driver and have averaged 25K miles a year for the past 30 years or so. With that said these brakes can stop me faster than I could without the assist. The best thing to do is take it out somewhere that is deserted and get it up to 50 mph or so and slam on the brakes! Once you get a feel for them you will appreciate the extra stopping power. The first time I hit them I too felt like "WTF?" I took it out and tested them several times and like I said there is no way I could stop that fast with non assisted brakes. We probably get 10-15 feet better from 60 mph than standard brakes.

 

[Bay33saw]

See^^^ If Greg says it's a good thing to do it is....

 

[BobsTrail]

I was testing on a wet road one day and if you are trying to do hard stops, you may also activate the anti-lock brake feature. That will give you a whole new sound you may not have heard from your T4R as it quickly brakes and releases. The good part is you can still steer while this is happening.

 

[Coveman]

Many thanks for the information.
Now that hydro boost seems to be the primary culprit in this case. Why would Toyota think my leg is not up to the task?!

I'm grateful for this discussion, as my wife and I haven't yet experienced the brake assist functionality and now have a heads up.

The hydro boost is really a neat component (although crazy expensive) to have. On my full size chevy truck I have a vacuum booster which has pretty much the opposite effect on panic braking...like, are the brakes gonna do anything? This is exasperated by modern engines not producing nearly as much vacuum as in the 60s when these vacuum boosters were rolled out, so if you hit your brakes a couple of times in succession, you've got no boost.

They've created electric vacuum pumps to assist with this problem on some vehicles and chevy also has a hydraulically powered hydro boost that they've used on light trucks for a while now. I looked at putting one of these on my truck but like I said, pretty expensive.

One thing I learned was that the folks that put big brake kits on their cars (and a set of Brembos can easily set you back three grand) often wind up with L E S S braking power due to the brake master cylinder / booster not supplying them enough force to work!

Anyhow, thanks everyone for schooling me up! :wave:

 

[1000MPH]

...Why would Toyota think my leg is not up to the task?!...

1.1 Billion reasons

 

[Bitsphere]

.., so if you hit your brakes a couple of times in succession, you've got no boost..

I would like to experiment with this, because in the past I used to do intermittent braking to override the ABS on wet conditions to avoid losing control. Now with this new feature, I would love to know how to override it, considering my jolty reflexes, which had often made my wife startle.

 

[1engineer]

I would like to experiment with this, because in the past I used to do intermittent braking to override the ABS on wet conditions to avoid losing control. Now with this new feature, I would love to know how to override it, considering my jolty reflexes, which had often made my wife startle.

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.

 

[JB.]

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

my 4Runner "SR5-013" decided to continue slowing rapidly and sustain a longer period for engaged brakes eventhough my foot left the brake pedal instantly.

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.

 

[Coveman]

I would like to experiment with this, because in the past I used to do intermittent braking to override the ABS on wet conditions to avoid losing control. Now with this new feature, I would love to know how to override it, considering my jolty reflexes, which had often made my wife startle.

On the Chevy this wasn't a good thing, without the boost you lost a significant amount of braking force and it left you white-knuckling wondering if you'd stop in time. Lots of folks complained to the ntsb but couldn't force a recall. Chevy eventually released a tsb that included a different proportioning valve and different rear pad material. My research suggested a straight bore master cylinder and larger wheel cylinder, and a hydro boost were also options. Having said that I'm enjoying the prospect of zealous stopping power! :hatsoff:

In your case if you search the forum I think you'll find a number of posts discussing VSC and ABS and various mods. Good luck!

 

[Go JayBee]

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.

I agree...learned about the 3 S's many years ago. "Stomp-Stay-Steer". Sounds crazy, but it does work.

 

[eddiebx]

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.

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.

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