[Fede]

Hi, I’ve got some unpredictable understeering. My alignment is toe=0, camber: front - 2° rear -1.5°.
I’m on snow tyres, Nokian WRG2. Road condition: moist... not dry, not full wet, no mud, no ice (temp 41F).
I call it “unpredictable” because it happen when it shouldn’t. Slow corner (20 mph), not in high speed corner because I’m very careful, but I think it will be the same.
In normal driving, I brake before the corner than I leave the car go, no brake or throttle. In tight and slow corner I’ve got this bad surprise...I wrote bad because the understeer happened at low speed and I was totally unprepared! It is really noticeable, the car seem shaking, a part from not cornering well.
I’ve done some tests, same corner and conditions: if I brake to have the same entry speed (20 mph) and then I apply some throttle, (thanks to S-AWC) the car turns really well, perhaps slides a little but it’s really predictable and the cornering speed is higher than the case where I brake and I let her go without throttle.
The problem is that when I’m in spirited driving mode, I can expect some reactions like understeer, oversteer and I’m prepared...but in case like the other day, I was driving relaxed, the entry corner speed was slow and the high understeer scared me! You know before entering a corner if the speed is right to avoid problem, to have perhaps problem or to have big trouble...I was in the first case.
I thought to rise the front tyre pressure but It seems me to be high: 35 psi front and 32 rear. Is it correct? How can I reduce the problem?

Thanks

 

[irmerm]

1. moist roads are slick roads. If there's any surface contamination in the particular corner you're going around, your entry speed may be too high for the corner at hand and you get understeer
2. You're on snow tires

 

[Fede]

Ok but without snow tyres and perfect road condition if I get the grip limit I think my car will understeer again

 

[chkmgnt59]

What irmerm said, you're on a slick road, and you're on snow tires.

On a dry track w/ good tires, you won't see the issue.... assuming you're driving right. If you're talking true racing conditions, you should be on the throttle in the corner, not drifting through it. As you point out, the car will work out the issues, but only if you give it power to do so. On a public road, you shouldn't have understeer issues, you'll be going too slow.

 

[Fede]

On a public road, you shouldn't have understeer issues, you'll be going too slow.

This is the point, I was going slow, so you can immagine my surprise...I'll try to keep always traction when cornering, not only during spirited driving.

 

[chkmgnt59]

you were sliding b/c it was wet and you have snow tires. simple as that. any application of power would have fixed it

 

[Ryan P]

^Not to mention there is always a good bit of debris on the road during this time of the year. Cinders, rocks, dirt, salt, etc. Traction will be limited.

 

[Optiblue]

Try it again with ASC one off

 

[Fede]

Settings

Yesterday, with normal tyres (no winter tyres) I’ve done some test, under heavy rain conditions.
I can have a lot of understeer only if I get inside the corner without throttle. Otherwise, braking a little more before the corner and then applying some gas (better more than less) with the engine over 3000 rpm make the car steering like on rails! Really, it can be unbelievable how it turns at speeds that without throttle will mean a crash without any doubt!
But, playing with gravel tarmac and snow, I’ve noticed that with tarmac there is more understeer than in snow mode. In snow, the car slides a little but with all the wheels, in tarmac there is at the beginning some slipping at the front (not too much). That seems to be a little in contrast against what I’ve read...some guys feel better during autoX without snow mode because there is less understeer...

 

[KickAss]

In SNOW mode, your diffs stay locked even after sensing steering angle change thus still sending power to all 4 wheels at that point. It does the same in Tarmac mode too, but, Its steering angle threshold to unlock the diffs is lesser compared to Snow mode. This should help you understand why your car is behaving in a certain way in the different modes.

This will also help you understand why you can cause diff failure if you use the wrong mode in the wrong conditions for extended periods.

 

[TheBlade]

In SNOW mode, your diffs stay locked even after sensing steering angle change thus still sending power to all 4 wheels at that point. It does the same in Tarmac mode too, but, Its steering angle threshold to unlock the diffs is lesser compared to Snow mode. This should help you understand why your car is behaving in a certain way in the different modes.

This will also help you understand why you can cause diff failure if you use the wrong mode in the wrong conditions for extended periods.

I'm just asking because i'm a n00b and haven't seen snow in years (living in Phx, AZ). To correct the understeer he was getting with the snow tires on, you're saying he should:
- Have it in snow mode ?
- Have it *not* in snow mode ?

I really have never been able to push my Evo with traction limitations as I never see anything less than 75 degrees and 15% humidity. (today is 111 and 4% )

 

[GSXRiderK6]

Why is the psi so high in the front tires? The higher the psi, the less grip!

 

[Evo X_X']

I'm just asking because i'm a n00b and haven't seen snow in years (living in Phx, AZ). To correct the understeer he was getting with the snow tires on, you're saying he should:
- Have it in snow mode ?
- Have it *not* in snow mode ?

I really have never been able to push my Evo with traction limitations as I never see anything less than 75 degrees and 15% humidity. (today is 111 and 4% )

In wet conditions it's actually better to have in gravel mode. To fix his under steer he should just get better tires. If its wet youre going to slide a bit no matter what

 

[TheBlade]

In wet conditions it's actually better to have in gravel mode. To fix his under steer he should just get better tires. If its wet youre going to slide a bit no matter what

I'm sorry I was too distracted by your avatar to read what you wrote.....



haha, okay gotcha When I first read the OP, I was thinking it sounded like he would be better off on all season tires and it would likely make the difference. As I read on, it made more sense that the AYC and ACD can't do their magic unless you actually give it throttle to power the wheels though.

What I think I learned:
- If it's wet, put in gravel mode, don't be afraid to apply some throttle if the car starts to slip.
- Use snow tires in the actual snow, if the snow melts, go back to all season tires.

 

[KoreanEvo]

In SNOW mode, your diffs stay locked even after sensing steering angle change thus still sending power to all 4 wheels at that point. It does the same in Tarmac mode too, but, Its steering angle threshold to unlock the diffs is lesser compared to Snow mode. This should help you understand why your car is behaving in a certain way in the different modes.

This will also help you understand why you can cause diff failure if you use the wrong mode in the wrong conditions for extended periods.

so obviously, snow is for when you're actually driving on snow.

now, when it comes to gravel, people seem to have their own opinion.

my car stays on tarmac 99% of the time because i live in ca where it doesn't snow and it rains maybe 10 days/yr. when the road gets wet, i switch from tarmac to gravel. some people seem to think wet surface still calls for tarmac.

what do you guys do? do you use tarmac for wet roads or do you switch to gravel?

 

[Fede]

In SNOW mode, your diffs stay locked even after sensing steering angle change thus still sending power to all 4 wheels

This is not really clear... If I use the gas there is always power going to the wheels an if I don't use it there isn't, maybe at that point the wheels speed is still locked (front-rear) so if the front axle wants to spin the ACD try to stop it.


But it' only theory because I dont think that is the only change.
In the same corner, same (not really high) speed, same amount of gas:
- tarmac more understeer at the beginning and than a little oversteer
- snow less understeer ad a little of sliding
At that speed I can't see the ACD working in the dash but only the AYC, in the same way. I know that it's only a stupid indicator but that led me to think that there is some influence also in other parts of the S-AWC controls, not only in ACD working strategy.

Maybe sometimes is better sleep than thinking too much!

 

[Fede]

As I read on, it made more sense that the AYC and ACD can't do their magic unless you actually give it throttle to power the wheels though.

:yeahthat: the difference when there isn't a good grip, between make the car cornering without gas and with a good amount of it, is more or less like day and night

 

[Fede]

In wet conditions it's actually better to have in gravel mode.

I'm trying to understand why seems to me that snow mode it's still better...

I agree that using snow mode on high grip surface couldn't be a good idea, not for mechanical problems (that I don't have proof of them) but because in cornering performance I don't see any improvements.