Anti lock brake problem

Perhaps it's time for some new tires.

Tom

 

<div class='quotetop'>QUOTE(qbee42 @ Oct 17 2007, 07:27 PM) [snapback]527147[/snapback]</div>

also if it was the first rain of the season it will lift up all the oil that has been on the road all summer, nothing will brake well on that...

 

Did you go over some bumps when this happened? This has been known to trigger the system due to the wheel being in the air while going over the bumps. You loose all braking for a second or so. It's enough to panic anyone!

 

<div class='quotetop'>QUOTE(czjohnson @ Oct 17 2007, 07:25 PM) [snapback]527145[/snapback]</div>

Just had the same problem with my Prius. Replaced tires this summer so that wasn't the problem. Went off a highway exit on a rainy day, braked lighly to go around a bend and completley lost control because of anti-skid - and ended up swerving into other lanes. Luckily wasn't hit by other cars. Had the car checked out and no problems spotted.

 

<div class='quotetop'>QUOTE(OakHill @ Nov 23 2007, 10:54 AM) [snapback]543207[/snapback]</div>

You won't loose control because of anti-skid; if anything, the VSC will keep you from going out of control. If you push your tires beyond the limits of physics you are going to go in a direction you never intended, even with VSC. The VSC will try to keep the car from spinning, and will attempt to make it go where you point the wheel, but there is only so much that can be done to overcome bad traction or overly aggressive maneuvering.

I don't know the condition of your tires and the road, or how you were driving, so I can't say for certain that VSC was blameless, but the odds favor that assessment. Other posters have had the same experience, where they feel that VSC did something that it shouldn't, when in fact there was a loss of control that would have been worse without VSC.

Tom

 

I agree with qbee that you will not lose control because of skid control (VSC - Vehicle Stability Control). Either the road conditions were too slippery even for VSC, or your VSC has become defective and failed to operate properly.

To czjohnson: If you are convinced that the road itself was not slippery enough to have caused this, then there's something wrong with your brakes. ABS will cause the brakes to pulse and add a little to your stopping distance, but properly-functioning ABS will not do what you described. Take it back to the dealership (or a different dealership) and insist that they drive the car to experience what is happening.

 

Something just does not add up in the usual way. Properly functioning ABS/VSC are very easy to live with, and any failure mode has the various warning icons on the screen and warning lamps on the dash

The only time ABS will increase stopping distances is on gravel roads and in deep snow. Especially on gravel, if you lock up the brakes, the tires dig in and you stop faster. On dry pavement, once the tires lock up, you lose steering and directional control.

Driving back from the hobby farm today, the roads were quite nasty thanks to the frozen slush. I had the Prius this time, with the studded Goodyear Nordic tires on. Tried some silly manuvers on the gravel side road leaving the hobby farm, and at no time felt the car was trying to take control from me

Actually, with the studded tires, I really couldn't get the car to do much of anything beyond normal behavior

I didn't go out last weekend, and drove around the FJ with the studless Toyo Open Country G-02 Plus winter tires. We had slick roads last Sunday too. In an empty parking lot I was able to get the VSC to chime in terror by getting up to 65 km/h, then violently taking the wheel to full lock left or right. Nothing dramatic, just a lot of buzzing from the brake boost pump as it pulsed one of the front wheels to keep the Cruiser on the intended path

With an FJ Cruiser, once you shift from 2WD to 4WD, you disable the VSC. I was then able to get some gentle spinouts on the parking lot, but the tires stick pretty good. They're not as grippy as good studded tires, but close enough and no noise.

I will admit the traction control especially behaves quite differently between the Prius and the FJ. The FJ allows gentle wheelspin, but if I stand on it, the brake will apply on the spinning tire, then engine output will decrease.

The VSC is more aggressive on the FJ than the Prius, probably because the FJ has a much greater chance of rollover. The ABS appears to work the same between the FJ and Prius

If your Prius is actiing like that, with good tires on, and the dealership can't duplicate the problem, there is something else going on. Is it the same stretch of road, perhaps an oily section?

 

This thread doesn't make any sense, except for the experienced folks who have already said "this doesn't make any sense." I've had ABS activate, and I didn't have problems. I've driven in some really nasty weather (even last week) on the lousy stock tires and I didn't have any problems. I've had VSC kick in due to a skid and the car straightened up before I had time for corrective actions of my own. Generally speaking, if you go off the road while ABS is activated then you shouldn't have been doing whatever you did. The only faults I can think of that would cause this condition would render a car completely un-drivable.

 

VSC is strange

Hi all...I had a similar experience about 3 times now during my 2 months so far of having my Prius 08.One instance for example - Dry day, no oil evident on the road, going less then 20MPH turning slightly into a right turn-out lane, and all of a sudden by VSC kicks in - and my car jerks a little to the left and right. Felt like I lost control when that thing kicked in. Not even sure why it did... totally unexpected. Felt like if that happened to me on a wet road or just a rainy day - I would have skid --- opposite of what its purpose!Strange.

 

I've been spooked by the ABS system several times. I looked up this forum just because of it. Here is what I'm experiencing:

ABS 'kicks in' because of a bump in the road. Usually happens when I'm braking before going into a turn, sometimes when braking before a light. I'm a fairly 'light' braker, ie I anticapate the stop and don't hit the brake too hard.

So the symptom is, I'm in the process of braking, say for 15' before turn or stop. In the last 5' I hit a bump, ABS kicks in, and suddenly I'm going 2-3 feet without brakes. Feels like I've lurched ahead, which may be what others have described as VSC loss of control.

I've been driving since before ABS was invented, and spent ten years prior to Prius driving a Corolla wagon, and have NEVER felt anything like this. I've never had bumps kick in ABS on another car (Yes, the ABS light comes on!), whether Voyager, S70, Mercury or rentals.

If this is at all common, it is going to cause an accident.

I know this thread is a bit stale, but I was searching specifically for this problem.

 

REMEMBER: ABS doesn't help you stop shorter compared to non-ABS brakes. They help you MAINTAIN CONTROL while braking instead of locking up the wheels.

If you were braking and ended up a carlength ahead of where you intended to stop, you did not brake soon enough.

 

Liberrian, I've experienced what you're describing - coming to a stop and hitting a pothole or a large groove in the road.

I think what we're feeling then is the system STOPPING regeneration. Primary 'braking' force under normal conditions is regeneration - drag from the motor acting like a generator. When we hit a bump that causes the rotation of the front wheels to do something odd, regeneration is disabled, and we feel that lurch before we increase brake pedal force, or the system kicks back in.

That's what it feels like to me.

 

It's the transition from regenerative braking to friction braking. The "loss of braking" sensation is discussed in many other threads.

Tom

 

As above, it's normal.
Yup, it induces panic, even in me, expecting it. I don't think it really lengthens stopping distance much. Perhaps 1/2 car length. If that's a problem, you're leaving your braking too late!
They just repaved the road where I felt it most often.
One problem solved. Twenty million to go.

 

If it were just a sensation, it would be fine. I think there is a definite effect though - as I said, only a foot or two, and I've only noticed it when I'm going fairly slow anyways - so maybe I tend to be in regeneritve mode more than typical, but it is disconcerting!

 

You can't have the sensation without some physical cause. As you state, it's a very small hit in braking distance. Many other factors cause an even bigger variation is stopping distance. Any good driver understands that braking distance varies and plans accordingly.

Tom

 

Quote "I started to brake and the anti-lock, skid control started up."

I had the exact same experience today. I noticed that the ABS gradually (~3 months now) started to kick in as if the tires were skidding.
Today, I entered a curve and the ABS decided to brake for me, and I almost went into a spin. Few minutes later, as I was braking the ABS kicked in, and it was as if I had no brakes, ended up missing my turn and had to take the next street. Road conditions was good, dry. What the crap... I will be taking the car to dealers to have it looked at.

The ABS makes this unussual grinding sound. Not like when the ABS normally works.

What is wrong with the ABS system?

 

Yes, I agree. Something wrong with the ABS/VSC. I had the same experience today. It seems to be common in the thread. Taking to dealer soon to have it checked out.

 

Dog Gone Prius 2012 has this same problem. I been driving the same road for several years, and actually driving slower than ussual, then the ABS/VCS kicks in and throws the Prius closer to the guard rails. What a scary moment. I was just coasting through the curve, road was dry, tires just passed inspection.