The bigger treadmill roller size myth, and how roller size affects your treadmill

Introduction

We are often asked about the roller size of our treadmills, and there’s a prevailing myth that a bigger roller is better. This post will hopefully clarify some questions about the size of the treadmill roller. We explain the design specification for our treadmill rollers, and hopefully we can kill the bigger treadmill roller size myth.

The short answer

Roller size is just one factor in the design of the treadmill drive system. When a treadmill is designed with the correct motor, rollers, and top speed, the running surface will be smooth. What’s more is that the system will be durable, so things will stay smooth!

NoblePro treadmills are installed with precision-engineered 55-millimetre front roller and 45-millimetre rear roller. Our entire power chain works together as a cohesive system to get the most out of the machine, and to keep you running smoothly.

The detailed answer

This gets a little technical, but we’ve done our best to try and keep things as clear and simple as possible. If you still have any questions about what we (try to) explain here, please email us.

Taxonomy

Before we dive into the technicalities, let’s take a moment and define the components involved.

Motor

This is the engine of the treadmill. You can change the power output of the motor to make the treadmill belt go faster or slower.

Motor Pulley

This is a spinning disk that connects directly to the Motor. This connects to the Roller Pulley, and the connection between them is how to transfer power from the Motor to the Roller.

Roller Pulley

This is the spinning disk that attaches to the front Roller, and connects the Motor Pulley. This component transfers the power from the Motor Pulley to the Roller.

Rollers

There are usually 2 Rollers in any treadmill, one in the front, and one in the back.

They are like big rolling pins. The Running Surface stretches across the two Rollers in a loop, turning in sync to keep the surface moving. The front Roller connects to the Roller Pulley, and this is the final step in the power chain from the Motor to the Running Surface.

Running Surface

This is the flat sheet that you run on. It stretches across the Rollers, and the front Roller transfers power to it to make it move.

RPM

“Revolutions Per Minute” is a measure of the power output of the Motor.

How Roller size affects power transfer

The visualisation below describes the relationship between the parts involved:

1. RPM
2. Roller diameter
3. The force (F) exerted on the running surface

This interactive illustration was based on the excellent essay “Gears” by Bartosz Ciechanowski.

Dragging the slider changes only one thing: the diameter of the roller. The power output (RPM) of the motor stays the same, and because of the change in roller size, the force exerted on the running surface changes!

The force increases as the roller size decreases, and decreases as the roller size increases. This is an inversely proportional relationship.

What this means in practice is the following:

1. Decreasing the roller size means the running surface gets more force applied to it, but can damage the treadmill because the rollers need to spin faster to make the running surface move fast enough.
2. Increasing the roller size means the running surface gets less force applied to it, which may seem like a good thing, but in fact, the running surface can slip as you run. Further, the motor will need to increase its power output to be able to exert more force to prevent this from happening, which means you might end up needing a bigger motor to get any real advantage.

Finding a balance

So, the size of the roller is not the determining factor during design but rather the system as a whole. What you want are rollers that are precisely the right size for the motor and pulley size they connect to.

We spent a lot of time crafting each part of our treadmills to make sure that the rollers we picked are ideal for the power output of our motors, and the maximum speed of the treadmill. Rest assured that the components in NoblePro treadmills are up to scratch, and can hopefully go as fast (or faster) than you need.