question on icy driving condition

Hi echeng66,

Since you did not get the buzz , the VSC was not activated. Only ABS.

VSC requires a yaw error. That is a difference between your steering input and the direction the car is pointed and rotating about the center of gravity. Since you were downhill and steering straight, you probably did not have a yaw error. So no VSC.

The Prius brake pedal is not a direct linkage to the wheel cylinders of the brakes. I am not an expert on this though. So, I cannot tell you if your experience indicates a problem. I do not remember much if any brake pulsing when ABS is on though.

Remember the brake pedal controls both the electric and friction brakes, and the car switches between them automatically based on conditions and demand. So, the pedal does not activate hydraulics directly, I do not believe.

 

Here's the difference I see between dry ground and snow

ABS works on dry ground by preventing your tires from skidding because it is the most efficient way to stop.. and it allows you to steer while braking.

If you're sliding on snow, I don't know if the system realizes that you are sliding.. In this case, there's no feedback from the road to the tires because you're just drifting.

VSC as explained by donee, is not really used in this application

ABS if activated, you will feel pumping of the brake. Traction control makes no sound, but I don't think it is used when braking. I think I see it when your foot is on the pedal. But these are my assumptions, I'm not an expert.

What you need to do is buy snow tires.

Snow tires on FWD, or RWD is better than All season tires on AWD. Of course, snow tires on AWD are the best.. but Snow tires are pretty useful. And if your hill was actually icy rather than slushy or snowy, then nothing would have really saved you at all. In that case you need to drive over the curb and onto the grass to find some traction.

 

Yeah there is feedback. It would be simple to figure out some sort of centrifugal force sensor. If wheels are turned, then there should be lots of centrifugal force. If there is none, then your drifting.

 

Since you indicated that you had no problems last year, this year's problems are probably due to tire wear. From what I can tell, the first winter with new stock tires is probably OK but after a year's wear, you are pretty much in harm's way driving in snow/ice with stock tires.

 

from personal experice the abs works with out pulseing the pedal in the prius. I have hit many times on the snow where I hit the breaks and feel it grip hard let up and grip hard. and it will light up the trac control light. I also know that the vsc lights up the traction control with a pulsing high pitched beep.. I found this out in the wonderful wisconsin winters we have been having. turning in an intersection at 15 mph and hear a beep with the wheels cranked to turn. not sure what it did

 

I had a similar experience. The first year I slipped and slided. I thought the car just was bad in the winter. Next year it started again, so I bought regular snow tires. The problem went right away. I never get the VSC warning any more.
What you can do is just go buy some cheap rims and have the snow tires mounted on those. Just change them your self when the snow comes.

I work at a Vocational School and they swap my regular with my snow tires for free. Most places like this don't charge labor, so as long as you have the tires it should be cheap. They might charge for weights, but that should only be a $2-$3. Check in your area. Tires swaps are a simple thing, so I don't mind the students doing it.

 

I found the my prius to be a pig in the snow - until I got a set of Winter tires.

The stock tires are good for mpg, but not for winter conditions, something I found referenced alot in this forum.

I took others advice and bought a new set of wheels and winter tires, and so far have had a much more normal driving experience here in NH this snowy/icy winter. I still can slip, but I now can get up my driveway when it snows.

The reason for the new wheels - the cost of switching rubber (summer/winter) adds up, and a new wheel is about $120, so you break even over the life of the tire.

I did not put in the sensors on the winter tires - and happily the low pressure sensor came on then went off - something that the older models did not do.