Why Do Tractors Have Smaller Front Wheels And Large Rear Wheels?

The tractor was invented by John Froelich in 1892. This tractor looked nothing like the modern tractors. It looked more like a car of those days. But it had one distinctive feature that made it homogenous to the modern tractor. Its large rear wheels. To this day, tractors have large rear tires with tread patterns. But why do the tractors have small front and large rear wheels?

Tractors have large rear wheels to use the high diesel engine power for pulling heavy loads. The front wheels are smaller because they are just for directions. The steering wheel controls the front wheels directly for turning or moving in a straight line.

The tread patterns on the rear tires help the machine grip the surface when conditions are not ideal. These treads make the tractors adapt to any surface of operation: muddy, slippery, or uneven. The majority of the tractor models are designed to work in the fields where the surface is rough and high traction is required. 

In this article, we will understand the science behind the size of tractor tires. Tractors, like any other automotive machine, have seen the evolution. The oldest tractors don’t look anything like the tractors of modern times. Modern tractors have advanced technology like hydraulics, power breaking, and power steerings. But every change has a science behind it. 

Let’s dive into the details and answer some questions about tractor wheels.

Why do tractors have small front wheels?

There are multiple reasons for tractors to have small front wheels. These reasons include fuel consumption, better steering, and turning radius. In most of the models, the front wheels are small but in some 4 wheel drive tractors front wheels are the same size as the rear wheels.

Better steering

With smaller wheels driving becomes more effective. Steering requires less effort to turn the tractor on the corners. Not only trunks but the motion in a straight line also becomes smoother. Stability and smooth operation are traits of any high-tech machine.

Turning radius

With small front wheels, the modern tractors have a low turning radius. Turning radius is the capability of any vehicle to change direction or motion in a circular pattern. If the turning radius is high, it is hard for the vehicle to turn on sharp turns. This is the reason small cars and golf carts turn swiftly with speed.

Fuel consumption

Front wheels are small and light, used mainly for steering. This automatically makes them helpful when it comes to saving fuel. The engine has to pull less weight, which reduces fuel consumption.

Why do tractors have large rear wheels?

Tractors got invented to reduce the human effort required in agriculture and other strenuous jobs. In agriculture, activities like sowing, harvesting, and harrowing, require large amounts of manual labor. Tractors solved that problem by reducing time and effort to do these tasks. 

Earlier tractors had large metallic wheels that were heavy and sometimes not ideal for soft soil. Most of these tractors were assembled by manual labor in the manufacturing plants. With the development in the manufacturing process, tractors started to come out from assembly lines.

These tractors were designed based on their predecessors but evolved with the power of science. From engines to wheels to hydraulics to power steering, tractors are ever-evolving.

We will focus on the scientific reason why tractors have large rear wheels. Here are some reasons:-

To increase torque

Torque is the product of force and radius(distance between the center of the wheel and the point of force application). In this case, the radius of the wheels. As the tractor moves forward, force is exerted on the ground. With large wheels, the torque increases, due to which the hauling power of the tractor is high. And even the heaviest weight is pulled easily.

Not only the heavy load pulling but the tasks like harrowing and tillage get more power. Harrowing and tillage can look easy from a distance, but in a field that previously had plants and trees with underground roots, it is a nightmare. More machines break than any other while working on the field filled with roots.

Centre of mass

Generally, tractors are powerful beasts that have big engines. These engines are so heavy that all the mass is concentrated on the front end if tractor wheels were smaller. Large rear tires are bulky, and they help bring the center of mass to the center of the body. This way, rear tires get more power from the transmission without breaking up or front lifting. Although you might have seen the videos of tractors lifting front while pulling, that has nothing to do with weight but the power of the engine and traction. 

Ground clearance

Muddy, slippery, pits, uneven, and soft are traits of the farmland surfaces. Tractors have to tackle all these and more.

Crops that grow a bit taller than others need to be protected from the crushing power of the machinery. For example, tractor-mounted pesticides sprayers work by spraying the field area from proximity. Therefore the tractor has to cover the field driving through the crops. High ground clearance with big tires ensures that crops are not crushed. There is some damage still from the rear tires but limited due to less pressure. It is more pressing than destroying the crops.

Rear-wheel drive

Tractors have rear-wheel transmission from the engine. And these diesel engines are heavy and powerful. To maintain the balance and torque, the size of the rear tire is more. Suppose if the size of the rear tires was the same as the front tires, the tractors would have been a racing machine, rather than pulling and hauling.

Why do rear tractor tires have tread patterns?

The reason for the treads is traction.

Traction originated from friction can be a massive force in doing heavy work. The rear tires have so much traction with the tread patterns that it lifts the front of the tractors. This usually happens when a heavy load is being pulled. Traction makes the rear end of the tractor stationary and the front end lift.

Why are the rear wheels of the tractors bigger in size than the front wheels?

Unlike cars, tractors are designed to work on uneven surfaces. Therefore maintaining the center of gravity is crucial. The size of the rear wheels is almost double that of the front wheels. Tractors remain stable in loose and mussy conditions without tipping over.

Why are the rear and front wheels the same size in some tractors?

Tractors with the same size rear and front wheels are usually 4 wheel drive utility vehicles. These tractors work in extreme environments like on narrow hilly roads, surfaces covered with snow and rocks.

Same size wheels and tires help to increase the mass of the machine to increase the traction. 

Why do tractors have wide rear tires?

Pressure is force times area, the enormous force generated from the engine is uniformly spread on a larger surface area using the wider tires.

To reduce pressure

Tractors have wide rear tires to spread the pressure. Tractors not only use the surface to move on, but they also work on the farm surfaces. A large base helps in avoiding the creation of a steeper impression in the soil. the area with a deep impression or more pressure will see no plant or crop growth. Seeds won’t be able to germinate out of the surface of the ground.  

Why do old tractors have narrow front wheels?

Reduced point of contact

To reduce crop destruction and soil compression, small tires with narrow wheels became a technical factor.

For guiding lines

In large farms, sowing is done in a straight line, sometimes for many hectares. Without any fixed path, this can be a tricky proposition. Front wheels help the operators or drivers move in a straight line. the streak between the front and rear wheels becomes the guiding factor.

Why are tractor front wheels at an angle?

The tractors often have front wheels at an angle to minimize the steering. This feature was prominent in the tractors of the past. This was the time when tractors were not equipped with power steering. It was tedious to steer these giants. With the angled tires, the forward motion was smooth. The driver had to rotate the steering wheel a little to make big turns.

Why do some tractors have 3 wheels?

In the early evolutionary phase, some tractors had three wheels, 2 rare and one front wheel. The purpose was to reduce crop damage by moving on a small part of the surface area.

Tractor models with front tires almost joined were designed for some crop fields for protecting the crops from the tires. In the past, most of the work was done by horses. Plowing was done by a single horse which left a streak mark on the field. The single front tire used to fall in this streak for smooth movement.