Oversteer And Understeer: Understanding The Difference

As you turn the steering wheel, you expect your car to turn a certain amount and take the desired path. Understeer is a condition where the car takes a longer path around the corner. This happens when the front tires slip, leading to a wider turning radius than anticipated. This mismatch of a vehicle's handling and expectations can lead to dangerous situations as your vehicle can slide into the wrong lane while turning. Understeer can also be accompanied by light steering and tire noises while making a turn. 

Understeer is usually prominent in front-wheel-drive cars compared to rear-wheel-drive cars. Generally, it is caused due to bad driving habits. Understeer is most likely to occur in the following scenarios:

• Excessive braking while turning

• Accelerating into a turn

• Taking a turn at high speeds

• Loss of traction due to oil spills or wet road

When you brake hard while turning, a forward force is exerted on the front wheels of the vehicle. If you then try to turn the vehicle, the additional lateral forces, along with braking forces, exceed the tire's grip. This reduces traction and forces the vehicle to take a wider turn, resulting in understeer. Furthermore, accelerating too much while turning makes your vehicle squat at the rear, causing the weight to shift towards the rear. This leaves the front wheels of the car with little traction and creates an imbalance, causing the vehicle to understeer. 

However, other factors like tire pressure, suspension setup, and wheel alignment can also cause the vehicle to oversteer or understeer. Among them are the following:

• Less tire pressure in the front or more in the rear

• Stiffer front shock absorbers or soft rear shocks

• A high front end or low rear end

• Wider rear tires compared to the front ones

• Stiffer front sway bars and softer rear sway bars

  
  

When a car understeers, it covers more distance while turning. In oversteer, the car turns more than expected, ending up taking a sharper turn than expected. This mostly happens in rear-wheel-drive vehicles where the rear wheel loses traction, causing the rear of the vehicle to slide towards the outside of the corner, making the vehicle steer more.

Just like understeer, oversteer is also caused by several factors, including your driving habits and vehicle setup. While front-wheel-drive vehicles are more prone to understeer, rear-wheel-drive vehicles are more prone to oversteer. It usually happens when the driver applies more power than the tires can deal with while taking a turn. This makes the rear of the vehicle slip towards the outside. The same effect can happen by braking too hard while turning or by suddenly removing your foot from the throttle. Driving factors that cause oversteer are as follows:

• Accelerating too early into a corner

• Hard braking into the corner or mid-corner

• Lifting the foot from the throttle pedal while turning (also known as snap-oversteer or lift-off oversteer)

• Steering the vehicle aggressively while accelerating during a turn

Other than these driving factors, the vehicle setup can also cause oversteering. The following factors are among the most common causes of vehicle oversteering.

• Stiff rear shock absorbers or soft front shocks

• Low tire pressure at the rear or high tire pressure at the front

• Higher rear end and lower front end

• Wider tires at the front and narrower tires at the rear

• Softer front sway bar and stiffer rear sway bar.

  
  

Lift-off or Snap oversteer happens when you lift your foot from the gas pedal in the middle of a turn. Sports cars and race drivers who drive aggressively are prone to this due to increased grip at the front tires compared to the rear. When the throttle is lifted, the weight gets transferred to the front of the vehicle, causing it to dive. This makes the rear end very light and causes it to lose traction and slide. Most performance cars oversteer because they are designed to offer more grip on the front wheels and a large amount of power on the rear wheels. This means that traction is very likely to be lost at the rear wheels, increasing the chances of oversteering and lift-off oversteering.

There are many reasons behind vehicle understeer and oversteer, as mentioned above. The most common reason behind vehicle understeer or oversteer is the driving technique. Here are some useful driving tips that will help you improve your driving habits and reduce the chances of oversteering and understeering.

1. Reduce Your Speed: Reduce your speed to avoid understeering and going wider in turns. A slight and smooth reduction in power will allow the tires to grip properly, and a small corrective steering input will get you back on the desired path. Reducing your speed at corners also prevents oversteering.

2. Avoid Hard Braking: Similarly, reduce your braking effort and free up more tire grip so you can steer your vehicle effortlessly around the bend.

3. Do Not Accelerate Into The Corner: Accelerating into the corner by applying too much throttle can cause your rear wheels to spin faster. This leads to loss of traction and causes the rear of the vehicle to slide out, resulting in oversteering. If you are driving a powerful vehicle, gently ease off the gas to retain adhesion at the rear wheels and prevent oversteering.

4. Countersteer: Countersteering is a method used for preventing the car from spinning due to oversteering. While countersteering, the front wheels of the vehicle are turned in the direction opposite the slide. If you witness an oversteer and the vehicle is sliding towards the left, the steering has to be turned left too. This is done to catch the rear of the vehicle before it slides too far out of control. Once the slide is controlled and the rest of the vehicle starts to fall in line, correct the steering too. Failing to do so can cause the vehicle to fishtail and get out of balance. Countersteering is a skill that can be mastered only through practice and should only be attempted under supervision.

There are reasons other than driving habits that are equally responsible for vehicle understeer and oversteer and are related to the vehicle setup. These can be corrected by making the following corrections:

1. Check Your Tires: Your tires play an important part in vehicle steering. If your current tires are old and worn-out, it's time to change tires as they won’t provide optimum traction and can cause your vehicle to understeer.

2. Tire Pressure: Tire pressure can significantly affect a vehicle’s tendency to oversteer and understeer. It is important to use a tire-pressure gauge and maintain proper tire pressures at manufacturer-recommended values.

3. Check Your Car’s Suspensions: Ensure the vehicle height is correct both at the front and rear. Learn how to check a car’s suspension and ensure the ride height matches the manufacturer’s specifications mentioned in the manual.

4. Wheel Alignment: Ensure the wheel is properly aligned and the toe, caster, and camber angles are correct. Learn more about wheel alignment and how it can affect your car’s handling.

5. Sway Bars: Aftermarket sway bars come in different sizes and materials. For example, a stiffer sway bar on a front-wheel-drive vehicle reduces understeer and will also reduce oversteer on a rear-wheel-drive car. Some rear-wheel-drive cars understeer. In such a situation, you can use a stiffer rear sway bar to make the car handle more neutrally.

Although neither condition is safe, understeer is comparatively safer than oversteer. With understeer, your vehicle travels along a predictable path, even if it’s not where you wanted to go. However, oversteering can make your vehicle slide anywhere, can lead to fishtailing, and in the worst case, can lead to a rollover. For this reason, many new cars are set up with a bias towards understeer, especially front-wheel-drive vehicles. This is because understeer is relatively easy and largely intuitive to control and correct, hence safer. 

Whereas avoiding oversteering requires considerably more skill (countersteering) and very quick reactions. Another reason for cars being engineered with understeer is to allow a head-on crash rather than sideways. This allows the driver and passengers to benefit from larger airbags and impact-absorbing crumple zones in the vehicle.

There is no magic fix to prevent your car from understeering or oversteering. Some drivers even prefer their cars to understeer or oversteer, depending on their driving styles. If you are a laid-back driver with a passenger car, the key to saving yourself from either situation is to go easy on the throttle and brakes while negotiating a turn. To avoid driveability issues, perform routine car repair and maintenance. Finally, reduce speed and proceed with caution on icy or snowy roads. For more advice, refer to our winter driving guide.