Understanding Oversteer and Understeer

Understeer and oversteer are terms of vehicle dynamics. In simple terms, understeer is when the vehicle turns less than expected by the driver and oversteer is when the rear of the vehicle begins to drift hence the term drifting. These terms are defined based of the angle of the steering wheel position associated with the speed of the vehicle through a bend.

An example of understeer is when a driver turns through a bend and the front end of the vehicle will turn less then expected and the front end of the vehicle ploughs to the outside of the bend. Thus, reducing driver confidence and control. Oversteer on the other hand is the opposite, Oversteer is when the rear end of the vehicle wants to come around in a corner (visualise drifting as an example).  

Understeer is a common characteristic of usually front-wheel drive cars. With the front axles not only handling steering input but the weight of the car as well, front-wheel drive vehicles suffer from understeer with the weight of the whole vehicle pushing the car forward, causing the car to plough further to the outside of the bend. Oversteer is a phenomenon typically seen on rear-wheel drive vehicles. With the rear axles applying power to the ground, the rear of the car wants to come around causing oversteer as seen in the diagram above.