Skidding Automobiles

Speaking from experience, the direction of a 'skid' depends on the amount of grip at each tyre. If the tyres are locked up, the direction of the camber of the road seems to be the major factor, you'll always go downhill. On the race track, on a surface that is usually clean and flat with consistent grip, you tend to go straight on. On a bike, if you lock the front wheel, any imbalance of weight about the centre line of the bike will tip the scales that way. (Uneven pressure on the 'bars won't help!) One of the IAM tests I've taken is to lock the front wheel on my bike at 60mph. Sounds scary and takes a bit of bottle, but after the first time, it's easy!

Blimey plbmak......... I was a biker up until the 80's and I've only ever had one front wheel lock up and that scared the carp out of me.....!!

As you say though a slight imbalance or the camber of the road, left hand driving i guess would be opposite to right hand driving.... together with ,in a car, the amount of grip and which side tyre let go first would start the direction of the skid...

John.

As far as any reason that an automobile would skid towards the right; it may be due to the crown that is formed on a paved road so that water is directed away from the centre and towards the edges.

In the southeastern U.S.A. this crown is not very tall and invisible to the eye. In the northen states, however, it is pronounced to the end that it is very visible.

Now this may explain the tendency to skid towards the right, but is does not explain the reason for a skid to the left when in reverse.

Ing. Robert Forbus

He he. It was a cross between a race school and an advanced test! Two weeks later we were on the Nurgurgring (The old proper one), and all of the handling theory that you think is a load of useless bull suddenly makes sense! The purpose of locking the front wheel was to demonstrate to us overconfident testosterone fuelled petrol headed idiots that conventional wisdom does not always apply. At 60, going in a straight line, the bike is completely stable, even with all the forces involved in jamming on the front brake! (Applying it gently allows the forces to build up to slowly to overcome grip at a fast enough speed).

The direction is based on many variables probably very difficult to know but the crown on the road is perhaps a dominant factor but then it depends on what country (which side of the road) you drive. The main reason for the skid is that sliding friction is less than rolling friction. Hence, if you lock up your rear wheel(s) and not the front, the rear of the vehicle has less resistance and wants to go faster than the front. Which ever way is easier, to the right in the right lane of a crowned roadway since it is also down hill. This is why pumping, manual or anti-lock works since you have intermittent rolling to suppress the action of the slide. If you lock up all wheels then they tend to slide more equally and you will tend to continue on your current vector plus whatever other effects may alter your course but usually more gently and not the same as when the rear wants to pass the front.

Maybe this is what you're getting at. Most if not all consumer vehicles are very slightly (steering geometry) biased to drift right (in locations where driving and steering wheel is on the right (opposite in left)...this is for preventing a head-on in favor of off-the-road incident when control of the steering wheel is lost for any reason (such as sleeping or loss of consciousness, even inattention). [Digression: if you ever find your vehicle drifts away from road edge on a level pavement, you should immediately have the wheel alignment and steering geometry checked and corrected--for you safety and others'. End of digression.] The (that's right, the) other factor is that roads are typically either crowned or graded towards the nearest road edge (as above, typically on the right) for water shedding purpose. Gravity will tend to pull a rolling vehicle downward.

Skidding and the dynamics leading up to skidding (including driver habit and grasp on the steering wheel.) will tend to be simply magnifiers and accelerators of the tendency which is already operating before the panic braking occurred. So, as to the other posted responses, the exceptions to right skid tendency, would pertain to whether or not countervailing conditions or forces (such as mal-alignments, mal-inflations, banked curve, ...), were sufficient to counteract this general road-edge- drift tendency.

A "bike" would tend to skid right (especially for right handed operators) due to the natural tendency to extend the left foot (the center of balance) groundward (and also to the mounting/dismounting side of the bike!!) in attempt to maintain balance or prevent "landing" or spilling. Nothing too complicated in that regard. The bike's skid habit recapitulates the rider's bilateral muscle tone distribution and vehicle control habit!

Never extend a foot at 60, don't even take a foot of the pegs, not if you want to keep it, and keep control of the bike. thats a dirt bike thing!

Agree completely with that... I've seen on icey days a few bikers riding along with both feet out each side!!!

They couldn't possibly have the control they would need in those conditions...

I used to ride in trails events and you always had to keep your grip on the tank to get maximum control of the bike... Riding with your feet out in icey conditions is sheer lunacy!!

John.

Could it be the extra weight of the driver on the right side of the car applying more friction to the wheels on that side? Be interesting to see if it works the other way in a left hand drive car.

Hey....

But in india its right hand drive and its keep left that means the vehicle skids uphill....

simply, no.

One major aspect in the opposed question will be pressure distribution of the brake calipers. If your car has a worn out caliper on the right-front, you will curve to the left wile braking.

I am a former brake systems and ABS development engineer. Your vehicle should move in a direction consistent with physics and associated vehicle dynamics of the braking event. The subsequent vehicle trajectory, magnitude and direction (ie braking event vectors) will govern the skid event it has nothing to do with gyroscopic effects. and it is very dependent on gravitational acceleration, center gravity, center of mass and mass moment of inertia.

What about the Coriolis effect?

I think you mean the Kronenberg effect?

If I'm affected by the Kronenberg effect I Leave the bike at home! NEVER DRING AND RIDE!.

More to the point The back Wheel of my bike always seemed to kick out to the right in a skid. But I have had it go both ways. But with my car it would normally just carry on straite until it hit an unmovable object.

I did experement once in the snow with the car at about 40 and pulling on the hand break but that slid from one side to the other a few times until it just ended spinning around in circles. Great fun if you can gind a bit of desirted road and your lucky enough to have some snow.

I drive both cars and bikes. I have not experienced this phenomenon! The direction of skid is normally opposite to the direction in which you are trying to turn. It seems to be a simple case of the tyres being unable to provide the necessary centripetal force.

This effect is very common with 4wd cars. particulaly downhill in mud.

what happens is both wheels lose traction, bu tone has more grip than the other OR teh side with the crownwheel, causes one wheel to drive the other as thedrive shat has no input. In effect and the $W problem is that th wheels go in opposite directions one pulling up hill the other driving down. The resultant vector is generally a slide to the right as the crownwheel side bearing tends to hold that side up slightly more than the other side. It is one major reason to fit a limited slip diff in muddy territory as teh effects is a major cause of rollovers and loss of control.