Why Tyres Have Treads On Them?

The rubber grooves or galleries present on the tyre surface are called treads. They are of various shapes and designs. Have you ever wondered about the reason behind their existence or have you ever thought about the pattern of these grooves. Let's talk about the science behind them. 

Reason for making treads

The general perception is that the Treads are made to increase the traction between  the road and tyres. But the plane tyres provide better traction on smooth roads, as larger surface contact makes better bonding between the two.But their grip decreases on wet tracks due to hydroplaning.

What is hydroplaning?

When vehicles are driven on wet tracks the water forms a layer between the road and the tyre. This is called hydroplaning. It disturbs the contact between the wheel an track and hence make the vehicle unstable.

Why motorcycles have different treads patterns on front and rear tyres?

Treads on rear and front wheels of motorcycle

You might have noticed that the Treads in motorcycle tyres are in opposite directions. This is because of difference in the roles of the front and the rear wheels. The real wheels help in transfer of motive force while the front wheels are used for braking and steering. Since rear wheels transfer the motive force it must maintain good traction with ground in all conditions. So they have tread designs which helps in throwing the water away from the centre of tyre surface towards outside. The front wheels have treads in a direction opposite to that of rear. They guide the water towards the centre of tyre . This is because the front wheels do not have power in them, they are driven by the rear ones. They are used only for braking and steering. When you apply the front brakes, the front wheels start decelerating and the water between treads experience a pseudo force in direction opposite to their direction of motion. Hence they are thrown outside away from tyre centre, preventing any chance of hydroplaning. This increases the braking effectiveness in wet conditions.

Why 4 wheelers have same tread patterns in all wheels?

The aerodynamic shape of cars is  such that they experience very high amount of lift force when they move with high speed. So they can not tolerate any hydroplaning in front or rear wheels. That's why the tread shape in them are such that they guide water to move away from tyre centre preventing any chance of hydroplaning.