Quote:
Martin J.S. said:
Quote:
amir sarmad said:
Dr Phil, whats the diff between understeer and oversteer.
"Understeer" is when the car does not turn into a curve, but tends to go straight (or more straight) instead. "Oversteer" is the opposite: The car turns even more into a curve than the driver wants it to.
In critical situations, "oversteer" is a typical behaviour for rear-wheel drive cars and "understeer" is a typical behaviour for front-wheel drive cars (generally speaking).
Very true.
"Understeer" = too little
"Oversteer" = too much
It's a matter of simple (yet complex) physics.
The challenge for a carmaker has always been to make a good compromize between accellerating /braking or turning.
It is very hard to do both at the same time.
Imagine a wheel with a nice lowprofile tire rolling on asphalt. Its just rolling at 50 km/h.
If you apply any force to the wheel, the tire will react and its grip or traction will be reduced.
How much the traction will be reduced depends on the nature of the force applied to the wheel, and how many different forces are applied at the same time.
Lets say you have 100 points of traction at any given time.
100 points total.
Now, the moment you spend more than 100 points in any give maneuver, you will lose traction and the car will skid. Either understeer or oversteer.
If you brake in a straight line, the tire will need its traction abilities to avoid skidding on the asphalt. Let's say that costs 70 points of traction. Now youre down to 30. No problem, you still have traction left.
If you turn, the tire will need its traction to avoid skidding to the side or continuing in a straight line when you wanna go to one side. Let's say that costs you 60 points. So you have 40 points left. No sweat.
Now. If you brake AND turn the tire (steeringwheel) at the same time, the tire will have to use its traction to BOTH brake AND turn at the same time.
If youre going at the same speed as before, you will need your 70 points to brake, and 60 points to steer....but that's 130 points - and you only have 100 points of traction. So now what happens? Well, you lose traction, and as a result your car starts skidding.
Same thing happens if you try to accellerate and turn at the same time.
Depending on tire compound, car type, suspension and a bunch of other factors, you car will either oversteer or understeer.
Front wheel drive cars (FWD) usually understeer in corners, because they use their frontwheels to provide BOTH acceleration (and primary braking) as well as the steering. Some FWD cars compensate by using Torsen, Haldex or other differentials that help providing power to the tire with the most grip. Others still use electronic devises (such as ESP, traction control etc) to help reduce the risk of skidding.
Most popular tuning amongst FWD owners is lowering the car and applying wider and lower tires and rims.
Rear wheel drive cars (RWD) usually oversteer, since the power provided by the rear tires have a tendency of "pushing" the car from behind and make the backend of the car "overtake" the front. Try taking a large matchbox. Open it and empty it. Now use the empty "tray", place it on your desk and try to push it forward with obe finger on the back of the box - and then u get and idea of the RWD challenge.
4-wheel drive cars (4WD) - as a rule- have a tendency of steering pretty neutrally. Depending on the kind of 4wd system in the car.
When a balanced 4wd car starts skidding, it usualy happens slowly and controlled and noirmally with a slight tendency to understeer.
Mid engine RWD cars usually oversteer, but often do so very fast and very unexpectedly, since theire midship engine layout provide them with immense stability to a certain point. After that the car usually spins fast around its own axis.
Depending on carmaker and setup, this can be increased or reduced.
The 987/986 has a tendency of sligth understeer (due to Porsche's factory setup) which gives the driver a mild-tempered midengine car with loads of traction and less of a surprising oversteer.
Looking back, this was all my doing though. The way to drive the car is to be nice and smoove and progressive with the throttle, if your going to push do it gently and the car will play ball even letting wag the tail. Too much aggresion though and she will bite!!!!
