maci

iTrader: (3)

Well, I'll jump right to the subject. I would really appreciate your thoughts on this.

Ok, so I drive a MY02 wrx, with good summer tyres. It is 2 degrees, and I'm driving into a big sharp curve(to the right), which goes right up to the highway. So I'm driving about 70 km/h, and my Scooby should easily handle the curve(in summer time). But what happens is that at the begining of the curve, the car suddenly slips completely to the right, so much that the front of the car starts to point a bit to the back(more than 90 degrees slip). I desperately turn the driving wheel to opposite direction, car jumps back to straight position. Still I'm in the middle of the curve, so I take immediately right but the car slips again, this time stright ahead right towards a big pillar. So Now I don't have a choice and press the brakes as hard as I could, and the miracle happens, suddenly the car is back on the curve and I have full control.
Needless to say that it scared the sh*t out of me and the others in the car...

Sorry for the long post, but I thought I give you a clear idea of what has happened.
My problem is that in my 11 years of driving I have never experienced anything like this, and I have problems figuring out what actually happened. I'm thinking that I must have cought a bit of an ice, then I had summer tyres and then again I have 17 inch thin wheels, which I think are more slippery that let's say 15 inched ones.

Still this is an AWD, so what is going on ?

B.

mgg

The chances are it was probably oil or something on the road, thats my guess.

AvalancheS8

Just because it's AWD doesn't give it any more cornering grip in that situation, the AWD will help under acceleration, or where you are accelerating hard around a corner, but in a situation where you are driving at a constant speed it makes no difference, you are still reliant on the grip provided by the tyres, and that isn't necessarily any greater than any other car with 4 tyres of that size and type.

Don't make the mistake of thinking that it is magically stuck to the road just because it is AWD, unless you are driving hard enough that you would have been causing the driven wheels of a 2WD car to slide by using so much throttle, the AWD itsn't doing much at all, and you have no more actual grip available to get round the corner than any other car.

maci

iTrader: (3)

And what about the tyres, are they providing less grip because they are thin ?
I have also been under the impression that because the AWD, if one wheel slips, the AWD will give the power to the other wheels(the differential locks). At least this is what I read about it in reviews.

andy97

iTrader: (1)

This time of year the roads get be awfully greasy. I think you were carring too much speed into the corner. Have you got the OE geometry setup.

My car has the powerstation geometry and other suspension mods, which gives it a little oversteer on cornering. I have been gently finding when the rear end starts to slide and applying a little steering correction to straighten the car. This rear end slide only ever happens when the roads are greasy(this time of year) or newly rained after a dry period( summer).

Andy

AvalancheS8

No, generally speaking, lower profile tyres will give a little more grip, although they let go more suddenly. What is more likely to be a problem is the make of tyres, or the pressure.

As suggested by Andy97, there could be an issue with your geometry set up.

What you say about the diffs and AWD is true, to a small extent, but it doesn't really effect the cars cornering abilities, particularly in the conditions you were describing where there isn't much power being transmitted anyway. On a standard, non Type-R Scooby, the diffs can only partially lock, and if you get the car into a situation where you start to spin one wheel due to excess power being applied, and you don't back off, the diffs will allow most of the power to be spun away through that wheel, so it will be producing no useful cornering grip. What the diffs will do in this situation is put a limited amount of power through the other wheels, so the car will retain a degree of forward drive. Given a large enough space, this can be enough for the car to eventually pull itself straight if the driver keeps on top of the steering input required.

The point I was making is that the advantages of AWD in cornering situations only make themselves felt when you are trying to acclerate very hard at the same time as cornering very hard. In the situation your were in where you were likely using almost no throttle the AWD system does basically nothing to help, there is nothing it can do, all it does is put the power on the road more effectively than a 2WD car, so if you aren't trying to put lots of power on the road, the AWD can't help you.

Any given tyre only has a certain total amount of grip available, which has to deal with both cornering and acceleration loads, so if you use some of the grip by accelerating, you have less to use for cornerning, and vice-versa. This is where an AWD system can have and effect on the car's cornering abilities since it spreads the tyre load from accelerating between all 4 wheels, so it uses less of the total grip at each wheel for accelerating, which leaves more for cornering. However, if you aren't accelerating, then none of the total grip is being used up for accelerating, and so it is all still available for cornering, in this situation it doesn't matter if your car is AWD, 2WD or what, it has the same grip.

Remember, the AWD system doesn't give the car MORE grip it just means that the cornering grip is reduced less than a 2WD car when you are accelerating at the same time.

maci

iTrader: (3)

Avalanche & Andy thanks a lot for your inputs and explanations. Could you tell me what is the OE geometry ? (I'm still a newbie...) The car is very new, bought it with 4k km and have now 7 k.

SCOOBYD00

I've been dipping the clutch using the *e-brake* for ages to make her slide... enjoy it

andy97

iTrader: (1)

Most Impreza's are setup to understeer, especially when you are powering in and out of corners. Powerstation can realign/adjust your suspension to eliminate virtually all understeer. Change of the rear anti roll bar( to an adjustable) and drop links will improve it aswell. Better to have the mods and geometry done together.


Gives the car a much better turn in to corners, but it makes the rear a little less grippy, not by much though.

I prefer my car this way. With a little pratice you can feel the back end start to slide and correct for it, as long as you are not too heavy footed on the throttle to start with.

Fast in slow out- no wrong way round, slow in, fast out


Andy

maci

iTrader: (3)

Thanks Andy.
Forgot to say that the pressure is perfect(2.3 front and 2.2 back in BARs), tyres are the original Bridgestones.
I did feel the understeer a few times when accelerating harder inside the curve, that I find nice and fun But my experience was nothing like that, it was a complete loss of control for a few seconds.
Now I'm looking into some winter tyres

AvalancheS8

Winter tyres may be all that is needed. The OE Bridgestones aren't the best tyres around anyway, and no summer tyre is much good at low temps (less than about 5). If the temp was only 2 degrees there could have been ice or frost on the road if it was in a shadow or sheltered location.

A subaru dealer or a good tyre place will be able to check the geometry against the OE settings.

If you do get into a slide, try to keep looking the way you want to go, even if you need to look out of the side window to do it, and keep steering for that direction. You may need to wind on and off lots of steering as fast as you can, so try not to freeze up and be gentle with the throttle. Suddenly lifting right off just after the back end has stepped out will make it worse.

Have fun with your car, and be extra careful in the cold weather, Scoobies are a real handful in ice or snow conditions on the original tyres.