VSC off during braking?? An argument...

[Thai]

There has been much discussion (on other forums) in the past about Toyota's VSC (stability control) being off in favor of ABS when slipping while going into a corner and putting on your brakes.

My view:

VSC (stability control) usually detects a slip BEFORE the driver is aware of it. Therefore, it will intervene "subconciously". It will make small corrections even before the driver is aware that the car has drifted.

With regard to braking and slipping in a corner at the same time, i do NOT see the point of having skid control on WHILE braking.

For example, if you're exiting the highway at high speed onto a ramp, and your car slides out, the MAIN concern at this time to slow the car down. At this point, you have one or more wheel withOUT traction. Let's just say that the driver is aware of slipping and put on the brakes. At this moment, you want the car to slow down or stop. So, what matters MOST at this time is applying brake to the wheel with MOST traction. So, what does that mean??

Well, the 4Runner (and other SUVs) have ELECTRONIC BRAKEFORCE DISTRIBUTION (aka EBD). In the situation above, this system/computer will send brake power to the wheel with MOST traction to slow your car down. ABS will then pump these wheels.

If VSC was still engaging, then it will REALLY confused the computer...it is sending brake power to the wheel(s) with most traction (via EBD)...YET, those wheel(s) with traction may NOT be the wheels needed for skid control!! So, what is more important??

Two scenerios:

1. Trying to slow down while cornering with braking power going to the wheel to control the skid (stability control ON while braking), which may NOT be the wheel with traction. Therefore, it maybe useless! Your car is NOT slowing down because braking power may be diverted to wheels withOUT traction in an attempt to control the skid; or

2. Trying to slow down while cornering with braking power going to the wheel with MOST traction via EBD and ABS. You car will then slow/stop.

Well, i prefer scenerio #2.

What do you guys think?

 

[Thai]

Another way of looking at things:

We're talking more about when the driver DOES realize the skid and put on the brakes while turning a corner. In those instances, i want all my braking power to go to the wheel(s) with traction...no where else! And this is what ABS + EBD does. I do not want skid control to interfere and diverts braking power to the other wheel(s) that have no traction. That kinda defeats the purpose of ABS & EBD.

If you have no traction to a wheel, it really does not matter what you do to that wheel. You can apply all the braking power to that wheel, and it would do no good.

And if a few wheels do have "some" traction, then EBD will give "some" braking power to those wheels. ABS first came out to HELP you steer AND brake out of trouble.

 

[EDGE]

I agree I want all the braking power going to the wheels with traction.

So far I have just over 300 miles on my truck and a few times on snow covered roads where it snowed about an inch and got compacted, while I was turning I felt like the rear end just slid when I was braking and a few times I was going down hills and felt like the truck was braking weird but I will update myself and other as I get more miles on it.

Also I do not fully understand the VSC/stability control switch, you leave it off and in slippery conditions where you high have troble getting out you push it in, still reading up on that, trying to fully understand it

 

[Thai]

Edge,

VSC should be turned OFF only when off-roading. You want it ON in everything else...like driving in snow/ice, gravel, etc..

 

[Swaro]

No opinion on the VSC/ brsking thing as I'm not fully aware/understanding it yet. But I can say that I would hope the Toyota engineers pre-thought out ALL scenerios.

Toyota recommends engaging the center diff lock in adverse snow/mud conditions while driving ON road. This of course will defeat the VSC. The point probably being, in some on road conditions, traction is of a higher importance than skid control--speeds will be low.

 

[stylishauto]

4Runner...why it is glued to the road.

VSC,picture a sensor on each wheel monitoring wheel speed,then a sensor in the center of the vehicle to measure yaw,and another measuring steering wheel center.This is what VSC consisits of.The ABS keeps the wheels from locking up,keeping you in a controlled situation that even while braking,you will be able to steer in the direction you want to go.The EBD(electronic brake force distribution)transfers the braking power from the front to the rear,letting the vehicle stop level instead of "diving down" or ''dipping down"in the front during a sudden stop.VSC controls the vehicle when you would understeer or oversteer via the sensors that monitor wheel speed,yaw(picture a plane)AND steering wheel center,by taking the readings it will actuate the brakes and reduce engine output to reduce the tendency to over or under steer.TRAC maximizes the vehicles traction by smoothly and automatically transfering the grip to either the left or to the right,while the TORSEN center differential will transfer the torque to either the front or the rear differential.This all works together.Each system that is in place works off of each other in unison to give you the best driving scenario possible.Go to toyota.com,go to the 4Runner mini site and check out the 3d tech. portion,it will give some really good visual examples of how each system works.

 

[Swaro]

Thanks Stylishauto. I'm trying to learn as much as possible about these vehicles/systems. Although I have a basic understanding of them, scenerios such as Thai's when braking in a corner bring up lots of questions that some of us would like to know more about. I was told this evening that the V8 and the V6 engines are definitely not interference engines ( I'll still probe as the rep seemed a bit unknowledgeable/untrustworthy), so...I don't mind a belt if it fails and no damage is done to the engine. I'm posting my impressions of the V6 test drive in a different post.

 

[stylishauto]

No problem,glad I could shed some light.

 

[EDGE]

Edge,

VSC should be turned OFF only when off-roading. You want it ON in everything else...like driving in snow/ice, gravel, etc..

The button on the dash when pushed in turns off the VSC, it locks the differential, the manual says to use it in situations where one would get stuck and needed more traction to get out, off road , maybe one night if I have time I put down here what the manuals says but I'll sum it up

 

[Thai]

Edge,

Basically in situation where you need to spin your tires to get out....

 

[EDGE]

Edge,

VSC should be turned OFF only when off-roading. You want it ON in everything else...like driving in snow/ice, gravel, etc..

I just realized what you said here was exactly what my manual said your right, I was confused

 

[Swaro]

Sorry if I created some confusion, EDGE. I didn't intend to negate what Thai had said. I would think the VSC defeat switch is primarily for off road. But I'm sure I read in the owner's manual even Toyota says ok to use on road in really bad conditions--read it again. I could be wrong, two salesmen were hovering over me blabbering when I was trying to read. Anyway, it's not set in concrete, take it somewhere safe and experiment carefully--see how the vehicle reacts with it on and off. Obviously, the Big Brothers at Toyota have put these systems in place to help control the vehicle for your safety. But if they didn't get it right, I have a lot of faith in my own ability to control a vehicle.

 

[Thai]

Swaro,

You may be right. However, in snow or ice, you would want VSC ON to control any sliding. The only time that you should turn VSC OFF is when you're in deep, deep snow and need to spin your tires to get out.

In mud, you should turn OFF VSC only when you're going slow and at risk of being stuck in deep, deep mud. Again, wheel spin is needed in this circumstance to get out. However, for the average NON-off-roading customer, they are usually going thru mud at high speed on their way to work (for example)...in which case, VSC should be ON to counteract any potential sliding.

Remember, if you switch VSC OFF (via locking center diff), and forget that you did it, you can "bind" the center differential and cause damage to it when making a turn around a corner on dry land.

For me, i turn VSC ON for all of my driving...ONLY when i am off-roading do i lock the center diff and turn off VSC.

Thanks.

 

[Eric G]

2 weeks into owning my '02 4runner, kid kicks his ball out into the narrow street between park cars. I see it and "start" to brake then the kids runs out and I had to put in on three wheels (felt the rear passenger wheel come down).

To this day, without the VSC and ABS working in combination, I would have killed the kid and rolled the truck. I know I would have rolled my former Trooper.

First time experencing the VSC blink on the dash and beeping. Distracing at first, but I'm glad its there.

 

[EDGE]

2 weeks into owning my '02 4runner, kid kicks his ball out into the narrow street between park cars. I see it and "start" to brake then the kids runs out and I had to put in on three wheels (felt the rear passenger wheel come down).

To this day, without the VSC and ABS working in combination, I would have killed the kid and rolled the truck. I know I would have rolled my former Trooper.

First time experencing the VSC blink on the dash and beeping. Distracing at first, but I'm glad its there.

Certain side streets where kids play I usually just role at about 20mph

Glad to hear you are alright as well as the kid, I myself would much rather hit a parked car or role and miss the kid than hit a child, it would most likely be a no fault but still I don't need that in the back of my mind and today the parents would sue for millions

 

[jharris2]

Eric -

Has your heart stopped racing yet????

Good reaction and choice on your part. You don't want the feeling of hurting the child with you.

That's why I always mosey going through school zones -- it's amazing how many times I see people roaring through there at 40+ mph when the warning lights are flashing.... The kids don't think about the consequences, so we need to think for them.