Why Do Dirt Bikes Have Smaller Rear Wheels? (Explained)

Dirt bikes have many important components that help with their performance and rideability, including their size, engine size, and design features.

One dirt bike competent that often doesn’t get enough credit for helping with performance and rideability though is the wheels.

Which is strange, considering that the spoked wheels of a dirt bike provide the foundation for the entire bike, and have one of the biggest impacts on its performance and rideability.

If you’re new to dirt bikes and dirt bike riding though, you might be wondering how or why this is.

Well, it primarily has to do with the diameter and width of both the front and rear wheels.

As dirt bikes have smaller and wider rear wheels that provide better traction and acceleration and larger and narrower front wheels that provide more shock absorption and better steering control.

To see all the reasons why dirt bikes have different-sized wheels on the front and rear though, make sure to keep reading.

As we provide the full explanation of why dirt bikes have different-sized wheels in the rest of this blog post.

Why Do Dirt Bikes Have Smaller and Wider Rear Wheels?

There are several reasons why dirt bikes have smaller and wider rear wheels, which we’ve outlined below.

Improved Traction

The main reason why dirt bikes have smaller and wider rear wheels is for traction, as a wider wheel has more surface area in contact with the ground, giving the bike more traction.

This is essential when riding on loose or slippery surfaces where traction can be difficult to come by.

In addition, a smaller diameter wheel will also help to improve traction as it will have less rotational mass.

This means that it will be easier for the rear tire to grip and maintain grip with the ground. Providing you with more traction to work with when accelerating out of corners or climbing hills.

Faster Acceleration

In addition to providing more traction, smaller and wider rear wheels also help to improve acceleration.

Due to the fact that smaller-diameter wheels have less mass, which requires less energy or power to get up to speed.

As a result, you’ll be able to accelerate faster.

In addition, the wider width of the rear tire will also help to improve acceleration, as it will provide a larger point of contact with the ground. Which will help to transfer more power to the ground, resulting in improved acceleration.

Better Braking Performance

Smaller and wider rear wheels also help to improve braking performance.

This is because the smaller diameter wheel will have less rotational mass, resulting in less kinetic energy that needs to be dissipated when braking.

In addition, the wider width of the rear tire will also help to improve braking performance as it will provide a larger contact patch. Which will help to transfer more energy to the ground, resulting in improved braking performance.

Weight Advantage

Finally, smaller wheels also have the advantage of being slightly lighter than their larger counterparts, which helps keep the bike’s overall weight down.

Which can help to improve the dirt bike’s performance.

By improving its top speed and acceleration and making it easier to maneuver and handle.

Why Do Dirt Bikes Have Larger and Narrower Front Wheels?

While dirt bikes have smaller and wider rear wheels for improved traction and acceleration, they also have larger and narrower front wheels for several reasons, which we’ve highlighted below.

Better Shock Absorption and Handling

One of the main reasons why dirt bikes have larger front wheels is for the improved shock absorption and better handling that they provide, as larger diameter wheels have more surface area to absorb bumps and shocks from the terrain.

As a result, you’ll be able to ride over rough terrain more smoothly and with less jarring.

In addition, the narrower width of the front tire will also help to improve shock absorption as it will have less contact with the ground.

Which can help to dissipate the energy from bumps and shocks more efficiently and effectively, resulting in a smoother ride.

Not to mention the fact that a narrower front tire will also help the rider to more easily avoid obstacles on the terrain, such as potholes and large bumps that can make a ride uncomfortable.

Improved Steering and Control

In addition to providing better shock absorption, larger front wheels also help to improve steering and control.

This is because the larger diameter of the front wheel will provide more leverage when turning.

Which makes it easier to steer the bike and navigate through turns.

In addition, the narrower width of the front tire will also help to improve steering and control, as a narrower tire will provide more precise steering control as well as less contact with the ground, making it easier to turn.

Reduces Stress on the Bike and Shocks

One final reason why dirt bikes have larger front wheels is to reduce the stress on the bike and shocks, as the larger diameter front wheel helps to absorb more of the bumps and shocks from the terrain.

Which can help to reduce wear and tear on the bike, as well as improve its longevity.

In addition, the larger front wheel will also help to reduce stress on the front shock, as a larger front wheel provides a front-line defense to dissipate the energy from bumps and shocks, resulting in less wear and tear on the shock.

Common Dirt Bike Tire Sizes for Both Front and Rear Wheels

Common dirt bike tires range in size from 18 to 21 inches, depending on whether it’s a front or rear wheel and the type of dirt bike it is.

As front dirt bike tires usually have slightly larger diameters compared to their corresponding rear tires.

With common front dirt bike tires being either 20 or 21 inches in diameter and common rear dirt bike tires being either 18 or 19 inches in diameter.

How Wide is a Dirt Bike Tire?

Dirt bike tire width can range from as little as 80 millimeters or 2.5 inches up to 150 millimeters or 6 inches.

However, the most common dirt bike tire widths usually range from 100 millimeters or 3.25 inches wide, up to 120 millimeters or 4.25 inches wide, depending on the size of the bike and the terrain.

For example, a 250cc dirt bike on intermediate terrain that’s a combination of hard pack and loose dirt or sand will often have 110-millimeter tires.

As this 110-millimeter tire width provides a nice balance of performance for a wide range of surfaces, without overwhelming the bike’s power output.

On the other hand, a 450cc bike will often use a 120-millimeter tire on intermediate terrain.

Because the bike has so much power and is able to run that bigger tire even in loose material to provide maximum traction.

Are Wider Dirt Bike Tires Better?

While wider dirt bike tires can provide better traction and in some cases better handling, due to the tire’s increased surface area with the ground.

Wider dirt bike tires are not always better.

As there are many cases when a narrower dirt bike tire might be the better choice, depending on the terrain, the size of the bike, and its power output.

For example, a wider tire will not only be heavier but will also require more power to turn.

This can have a negative impact on the bike’s handling and performance, as the extra weight and wider width can make it harder for the bike to change direction and can make the bike feel sluggish, especially on smaller dirt bikes with engine sizes of less than 250cc.

In addition, wider tires can also decrease the maneuverability of the bike.

As they make it more difficult to turn the bike, due to the increased contact area with the ground.

Lastly, while wider tires can provide more traction, in some cases they can also provide less traction.

This is because the increased surface area can cause the tire to sink into softer surfaces, such as sand and mud.

Which can make it difficult to move forward and can cause the bike to get stuck.

So while wider tires can provide several benefits, they also have several drawbacks that should be considered before choosing, as wider is not always better when it comes to dirt bike tires.

Why Do Trail Bikes Have 18-Inch Wheels?

The reason why trail bikes often have smaller 18-inch wheels and tires is because of the higher side wall compared to larger dirt bike tires.

This higher side wall is beneficial in off-road and trail riding, as taller side walls allow the tire to flex more and be more forgiving in rough and rocky terrain.

Also, higher side walls help to prevent pinch flats.

Pinch flats or snake bites as they are sometimes referred to occur when the wheel and tire hit something with enough force that the pressure in the tire is overwhelmed and the edge of the rim slices through the tread and/or bead of the tire.

Final Thoughts

As you can see, there are several reasons why dirt bikes have smaller rear wheels.

As smaller rear wheels on dirt bikes provide better traction, faster acceleration, better braking performance, and a slight weight advantage.

Which is why it’s customary on dirt bikes to have a smaller and wider rear wheel and a larger and narrower front wheel.

Additional Dirt Bike Resources:

Want to learn more about why dirt bikes are the way they are? If so, check out some of our other dirt bike blog posts.