What is snap oversteer and why do you need to know about it?

[91cavgt]

This thread is mainly geared towards those that will drive their cars in a spirited manner, or race them. However, it is good information to know even if you don't ever plan to push the car at all.


As we all know, our Mirage's have very soft, comfy, and compliant suspension. This makes for a good ride, but it can be VERY dangerous if you push the car hard, or have to suddenly maneuver to avoid something in the road. The reason it can be dangerous is because of how much body roll this car has. Mitsubishi has done a wonderful job at trying to prevent snap over steer by adding stability control to the car. But if it is disabled, it can be very dangerous if you don't know what you are doing. Here's why;

Body roll is the tendency for the car to lean to the outside in corners instead of staying level. This leaning unloads the tires closest to the inside of the corner and loads the tires closest to the outside of the corner. There's not any problems with this if you are just going around a corner. So what happens if you go around an S curve at a high rate of speed or have to dodge something in the road? Well, the first corner is pretty uneventful as the car leans to one side, loading one pair of tires while unloading the tires on the other side of the car. But now you suddenly turn the steering wheel the other way to go around the other part of the S corner(or item in the road), and now the car goes from leaning really far one way to quickly moving in the opposite direction. This causes a very fast weight transfer from one side of the car to the other. It occurs so fast that momentum builds up and actually unloads the inside rear tire(the tire closest to the inside of the corner) more than in the beginning of the S corner. It unloads the tire so much that the tire looses traction with the road. So now, it is like going around a corner, quickly, on 3 wheels (2 in the front and 1 in the back). Because of this, the back of the car will now want to quickly go into over steer, or otherwise known as snap over steer since that 1 rear tire that does have traction, doesn't have enough traction to keep the car pointed in the direction you want to go.

Ok, so we now know what causes snap over steer, but why is it dangerous?

It is dangerous because the back of the car rotates so quickly that no amount of steering changes can correct it. You pretty much just have to ride it out till the car slides to a stop, if you are lucky enough to have the car slide to a stop and not hit anything or flip over. Snap over steer is not like drifting a rear wheel drive car, or just messing around and sliding the back of a car out while going around a slow corner. In normal over steer conditions, over steer occurs relatively slowly and is easily controlled with proper driver inputs. In snap over steer, the over steer occurs so quickly and so violently that there is no controlling it, especially in an under powered front wheel drive car.



I have experienced snap over steer first hand. Luckily for me, I was on a race track, but I was in the passenger seat of my car, and there was plenty of room for the car to come to a stop without hitting anything. The car was a 2002 Hyundai Accent, a VERY similar car, suspension wise, to our Mirage's. A driving instructor friend of mine(Porsche club driving instructor, Nissan club driving instructor) was telling me that I was taking a series of corners at Hallett Raceway wrong, and that he could shave 5 seconds off of my time. So I offered to let him show me which he accepted. The series of corners was basically an S turn (a left hand corner right after a right hand corner). So, we entered the first corner at about 60 mph, accelerated through the corner and started to enter the second corner at about 65 mph. This is where things went bad. My buddy was not used to front wheel drive cars, and he had never experienced snap over steer. The car had leaned really far through the 1st turn because of the large amount of body roll. When we approached the 2nd corner, my buddy threw the car the other way with never letting the car settle from the last corner. What happened next was terrifying. The rear of the car shot around and before my driving instructor friend had time to do anything, we were completely sideways heading off the track, while still doing 65 mph. Going 65 mph, sideways, across a grassy field, and the one thing that keeps going through your head is you are waiting for a tire to dig in to the dirt which would cause the car to start rolling.

This is why Mitsubishi installed the stability control on the Mirage's. This is why if you are out and about, PLEASE keep your traction control/stability control active. There is a time to disable it, but driving around on the streets on dry and wet roads is not one of them.

[gls2001]

The Philippine spec don't have the traction control.

[Mistah JT]

Didn't really read much of the above, too much reading haha, but I will add that the traction control has nearly killed me a few times. Driving very fast, and it kicks in when I am taking a corner, it rips the car back the other way and nearly sends me into the guard rail.
When I am doing this type of drive, I turn it off since I believe I can control the car better to not throw it the other way to help.

[91cavgt]

Didn't really read much of the above, too much reading haha, but I will add that the traction control has nearly killed me a few times. Driving very fast, and it kicks in when I am taking a corner, it rips the car back the other way and nearly sends me into the guard rail.
When I am doing this type of drive, I turn it off since I believe I can control the car better to not throw it the other way to help.

The stability control kicked in because you were on the verge of snap over steer, which if it happens then you will definitely be going into a guard rail. When snap over steer occurs, you can't do anything to regain control of the car. The key to prevent the stability control from kicking in is VERY smooth and slow changes on the steering, brakes, and throttle. Don't try to throw the car around, but rather finesse it around.

Slow into a corner, fast out. Brake only in a straight line as you can get on the brakes really hard if you are going straight, but if you are cornering and hit the brakes hard then the car will want to get out of shape.

[MetroMPG]

91cavgt: agree with most of what you posted.

I strongly feel that people who want to drive in a "spirited" manner should take instruction in racing/performance driving and skid control to get a solid understanding of handling approaching & past the limits of traction.

The stability control kicked in because you were on the verge of snap over steer, which if it happens then you will definitely be going into a guard rail.

That's not necessarily the case. He may have just been experiencing "garden variety" mild, controllable oversteer (from lifting off the throttle, or descending a grade in a curve, or being too abrupt with the steering, or a change in road surface traction...). If you're adjusting your steering input to account for a little bit of oversteer and then the ASC cuts in to "cancel" the oversteer, you will now find yourself heading more toward the outside of the turn. Sounds like that's what he's describing.

[Ares]

tl:dr

If you're racing the car, you will know how to handle it by the end of the day.

I may just import a car from the PI without all the airbags and driver-neutering systems.

[91cavgt]

91cavgt: agree with most of what you posted.

I strongly feel that people who want to drive in a "spirited" manner should take instruction in racing/performance driving and skid control to get a solid understanding of handling approaching & past the limits of traction.



That's not necessarily the case. He may have just been experiencing "garden variety" mild, controllable oversteer (from lifting off the throttle, or descending a grade in a curve, or being too abrupt with the steering, or a change in road surface traction...). If you're adjusting your steering input to account for a little bit of oversteer and then the ASC cuts in to "cancel" the oversteer, you will now find yourself heading more toward the outside of the turn. Sounds like that's what he's describing.

Good point!! I have taken my Mirage out and pushed it in some very long corners and never had ASC cut in, but I am also older than I used to be and am VERY smooth. I'll take it back out in a couple of days to see if I can get it to kick in to see for myself how intrusive it is, and how hard I have to push things to get it to kick in.

[MetroMPG]

I had the above happen to me on gravel in a handful of curves while driving in the economy rally outside of Montreal a few weekends back.

I wanted a little bit of oversteer, and I could get a little bit of it. But if I got greedy and lifted briefly to rotate a little bit more, the electronic nanny would take it ALL away from me! And then the little bit of opposite lock I had was taking me more toward the outside of the curve than I would have liked. Nothing a quick, instinctive correction couldn't fix, but still a little bit annoying.

[Mistah JT]

The stability control kicked in because you were on the verge of snap over steer, which if it happens then you will definitely be going into a guard rail. When snap over steer occurs, you can't do anything to regain control of the car. The key to prevent the stability control from kicking in is VERY smooth and slow changes on the steering, brakes, and throttle. Don't try to throw the car around, but rather finesse it around.

Slow into a corner, fast out. Brake only in a straight line as you can get on the brakes really hard if you are going straight, but if you are cornering and hit the brakes hard then the car will want to get out of shape.

Can't be, I slide it in my work on the sweeping corner and it still yanks the car the opposite way I am turning. I just turn the traction control off so it drifts a little. Much more fun and safer than me crashing haha

[foama]

I understand the very first post as a word of caution. Yes, 91cavgt is right about that in principle, but I really don't think we Mirage owners have much to worry about.

My neighbour has an old Citroen 2CV. That car has nill stabilisers. Tyre size is skinny 125-R15. Paired with independant suspension and the ability of each wheel to move about 50cm (about 1 1/2 ft) either up or down to feather huge potholes, it always leans to the side. When a normal person sits in the driver seat, it makes it lean sideways about 20°. A slowly taken curve makes it lean about another 20-30° outward. If you are not used to it, you can easily get sea-sick and get scared to death fearing it will instantly tip over. On regular streets, its more like a camel ride in the desert. In the sticks, you might well think it will throw you off. You need time to get used to it.

The point I am trying to make: The Citroen 2CV were made for decades and in great numbers, but I can not recall even one tipping over or flying out of a curve.
foama