Driving is something we all do on a daily basis. From going to work to picking up the kids from school, driving is an everyday necessity. With advancements like electronic stability control in modern cars, drivers have a lot less to stress about, but it is still important to know the dangers of being on the road. While driving, there are two important scenarios to keep in mind: understeering and oversteering.
In this post, we will explain more about understeer vs. oversteer, including how they both work and how they affect different types of vehicles.
Understanding Centrifugal Force
When discussing understeering and oversteering, it is helpful to understand the vehicle dynamics and specific vehicle dynamics terms. Centrifugal and centripetal forces are both at work when driving your vehicle around curves in the road. These forces work at the same time but pull in opposite directions. Centripetal force pulls a vehicle towards the center of a curve, and centrifugal force pushes the car away from the center. The ‘“center” refers to the inside section of the curve. If you were to form a circle with the curve, the “center” would be the middle of that circular path.
Another key point is that the faster the vehicle is traveling, the more powerful the centrifugal force. This force gains momentum the faster the object goes, pushing it further and further away from the center. Along with the centrifugal force, there is also lateral acceleration. This type of acceleration acts transversely to the driving direction of your vehicle. You most likely have experienced both at some point. Have you ever been driving fast around a curve? You might have felt the car pulling towards the outside of the road. Centrifugal force is a natural occurrence but having too much centrifugal force can lead to skidding and a dangerous situation. The best way to limit centrifugal force is to reduce to a low speed around curves.
What is Understeer
Let’s now turn to understeering. When you understeer on a curve or turn, the vehicle doesn’t move along the planned path of travel. Instead, the car moves on the outside of its intended path. This typically happens when the front tires don’t have enough traction for the turn, leading to an over-rotation. As the front wheels are rotating very quickly, there isn’t enough traction to move in the desired direction, making the car push wide of the turn.
What Causes Understeering
Understeering can happen in a few driving scenarios. This phenomenon tends to happen when the driver:
- Turns the wheel too sharply
- Turns the car too abruptly
- Turns too much for the car’s speed
When these scenarios happen, the front tires don’t have enough grip to move in the desired direction, leading to the nose of the car sliding out away from the center of the curve. This can happen in any driving environment, but it’s far more common in cold or wet conditions. This problem also occurs when the weight distribution is off and there isn’t enough weight over the front tires as you’re accelerating through a turn.
Here are the main symptoms of understeering:
- Car moves outwards from a curve
- Front tires screeching
- Vibration felt at the steering wheel
- Feeling a loss of grip on the road when turning
As these scenarios can be scary and worrisome, it’s important to understand how to fix the problem.
How to Correct Understeer
When trying to fix an understeer situation, you’ll want to attack the cause of the issue. That said, you need to be aware of the situation to understand what to do next. First, if you turn the steering wheel and the car isn’t turning as it should, don’t turn the wheel more. This can make the problem worse. You also don't want to hit the brakes, as this can lock them up and make you lose even more control.
One common way to fix understeering involves unwinding the steering wheel. If you’re turning a corner, slightly turn your steering wheel into the curve. This will help to properly align your wheels, reduce the steering angle, and gain traction. You should also ease off the car throttle to relieve the tension on your vehicle and not accelerate to a higher speed. This will regain some grip on your front tires and help go back to a steady state of driving. However, if that didn't restore much traction to your front wheels, try applying the brakes gradually to gain more control.
What is Oversteer
Oversteering occurs when the vehicle turns more than what’s intended by the driver, leading to the rear tires sliding outwards. This results from the rear tires trying to match the direction of the front tires, but there’s a loss of control. The rear tires can’t find enough grip for the high level of centrifugal force, which causes the back tires to spin. This scenario is especially common on the racetrack.
What Causes Oversteering
Oversteering is typically caused by the driver, but it can also happen from road conditions. When you oversteer, it usually happens as a result of one of the following driver actions:
- Hitting the throttle too fast in a powerful gear while steering
- Suddenly lifting off the throttle while steering
- Too much ‘trail braking’
In the first instance, it’s important to note this is most common in a rear-wheel-drive car. When too much power is applied on a curve, your rear tires sometimes can’t keep up. They lose traction and start to skid outwards. This happens because the wheels are pushed sideways and can’t grip the road.
In the last two scenarios, the driver's actions cause too much weight on the front wheels, leaving the rear tires with minimal grip. This will also cause an outward slide of the rear tires when turning into a bend. This oversteering scenario is called “lift-off” oversteering, which can impact all car types.
How to Correct Oversteer
In an oversteer situation, no matter the cause, you’ll want to keep the front wheels pointing in the direction you want to go. Even if your wheels are spinning, this means turning the steering wheel into the spin. This action helps your front tires regain traction on the road. This technique is called “counter-steering.” It may feel awkward to turn into a skid, but it’s one trusted way to get out of one. However, it's very important to turn at the proper angle, and you may have to add more steering input. If you turn too little or too much, the car can spin even further.
Cornering Effects on Different Types of Vehicles
Understeering and oversteering are two driving problems that should be avoided. Both cause the driver to lose control, which can end in an accident. However, when a car oversteers or understeers, it usually depends on the vehicle type.
Check out the following cornering effects on different types of vehicles:
FWD (front-wheel drive)
If you have a front-wheel drive car, it’s more common to understeer than oversteer. This is especially true when entering a corner too fast. However, if you lift off the throttle too quickly or brake too hard, this creates a high possibility of oversteering. This problem is often seen with sporty FWD cars when the driver turns too sharply, and the tires lose grip. Also, these cars are especially prone to lift off oversteering due to the light rear end and forward weight transfer.
As the weight of front-wheel drive vehicles is mainly in the front end, the rear tires easily lose grip. There is some weight transfer to the rear, but not much. As this weight is mostly in the front, these wheels can also have a hard time keeping up. This is why it’s common for the front wheels to push outwards on a curve.
RWD (rear-wheel drive)
When the engine powers the rear wheels on a vehicle, it’s more common to oversteer than understeer. This is especially true when entering a corner too fast or accelerating too early on a turn. You can also oversteer when lighting off the throttle or hitting the brakes, but the probability is lower.
Another important factor is that the engine is often in the front of the vehicle on an RWD car, adding more weight to the front end. While this creates a high level of grip for the front wheels, this decreases grip and traction in the rear. The rear end slip angle is higher than the front-end, the primary cause of oversteering. With rear-wheel drive cars, you need to be careful if you are an inexperienced driver and remember to have traction control to prevent these situations.
AWD (all-wheel drive)
Driving an AWD vehicle is the best way to avoid understeering or oversteering. As all four wheels are powered, this creates more traction and responsiveness on the road. However, AWD vehicles can still understeer and oversteer.
Here are the scenarios that can cause these problems:
- Entering the turn too fast
- Hitting the throttle early or too aggressively
- Braking
- Lifting off the throttle
As the driving forces are shared between all four wheels, oversteering and understeering are less of a risk on AWD and 4WD vehicles. However, it is still possible, so you’ll want to be cautious.
Specialty Performance Parts
While staying safe on the road is essential, you need the right parts to keep your ride running effectively. In fact, some parts can help with power and control, helping you stay away from oversteering and understeering.
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