Question about ABS systems?

[graywolf624]

Your driving on snow.. Even ABS isn't a miracle worker. When you brake and turn your splitting your tire traction force between turning and stopping. Do it on an already slippery surface, prolly in tires that arent for winner, and the abs won't matter. Sadly so many people assume cause you have abs and 4wd your invincible.. It may be alot harder but you still can royally screw yourself.. Thats why we see alot of them on there roofs around these parts during winter.

[ZfrkS62]

There is a difference between ABS and Traction Control. You don't have to get the wheels to lock in order to slide sideways.

ABS keeps the tires at approx. 25% slip, since this is where the most friction is created between the tires and the road. So when you slam on your brakes, the ABS hydraulic unit maintains the pressure in the system to control wheel lock up.

Traction Control Systems work along the same premise of controlling wheel slip in a straight line by either limiting the wheels to around 25% slip (launch controls) or less depending on the settings by scaling back engine torque, or by controling the yaw rate of the car by applying the brakes according to vehicle rotation. Oversteer will apply the outside brakes to keep the car from spinning out, or by applying the inside rear to pivot the car out of an Audi...er...understeer, situation. Or a combination of both methods.

You could always try the E-brake

[AlienDB7]

How hard were you braking in the impreza? Beside locking the wheels, one of the most effective ways to get a sideways is to take advantage of weight transfer. By braking, you're transferring weight to front of the car so there'll be less traction for the back. That's basically how trail braking works.. and to a certain degree, lift-off oversteer. Personally, I find lift-off oversteer very effective on snowy roads. No need to pull the handbrake or left-foot brake... just use a low gear, keep the rev up before the corner and left your foot off the pedal in the middle of the turn.

[coombsie66]

Well, it depends on the brake bias of the impreza, and what your other car is, if your other car is front wheel drive then that will probably have more brake bias to the front than the impreza does, having more weight over the rear wheels and the inertia of the diff drivetrain etc on the rear wheels to slow down as well.
The abs wont come into it as you said your not pushing the brakes hard enough for them to lock, and hence the abs issue wont come into it. You are just experiencing a nice bit of 'trail braking' in the scooby.
As graywolf said, when you turn in your tyres are then coping with turning as well as braking, and if your other car has a relatively compliant suspension set up then the rear will stay planted and it will plough on in understeer, i'd guess the impreza has a pretty stiff rear anti roll bar, hence when you turn in, the inside rear will become unweighted, and as your trailing the brakes too you have very little traction on the rear and it'll come around. The fact that its 4WB will also mean that your engine braking will be effecting the rear wheels as well as the fronts, not sure how it works with the trick electronic diffs they have but, it wouldnt surprise me if oversteer is easily provoked in it, especially in slippery conditions.

[nthfinity]

im trying to get this...

so you how slippery were the conditions you were braking +turning in? wet, snow, ice, dry?

under enough braking power, even with ABS, weight is lifted from the rear, and grip is lost; and lets you run a bit sidways... its usually pretty controllable when i've done it, but with snow tires, i just understeer off-power (in my jeep)

tires can make a world of difference in stopping power under the same conditions; and weight transfer could take place with one compound, and not another...

its also safe to say the subie has more brake bias in the rear then most FWD cars.

once a slide starts (sidways slide) abs doesn't know what to do, as you dont have traction along the line of rotational friction... often ABS systems freak out under that, and are constantly locking+unlocking the brakes... and doesnt really aid the driver either way... a stability program will apply brakes to recover traction at specific wheels...