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How to Choose the Right Timing Belt Tooth Profile 

timing belt tooth profile

One of the most important things to understand about timing belts is that not all options are created equally. Keep in mind that you're talking about something that is responsible for not only transporting, but also positioning-related applications as well. They deal with high torque, force, and even rates of acceleration. They're an invaluable part of any manufacturing environment and the material the belt is constructed from is only one small part of a much larger story.

Equally important is the tooth profile itself. This has a direct impact on not only how much power can be transmitted but also how much speed the belt is capable of and more. Because of all that, this is one of those properties that you do not want to leave to chance.

Types of Timing Belt Tooth Profiles

Overall, there are a few different types of timing belt tooth profiles that are available to meet your needs. Understanding each one and what makes them unique is the key to making the most informed decision possible regarding your upcoming project.


The first major type of timing belt tooth profile to concern yourself with is called the trapezoidal profile. When measuring the distance from the center of one tooth to the center of the next one in the line, the trapezoidal profile includes the following dimensions:

  • 0.08 inches, or MXL
  • 0.20 inches, or XL
  • 0.375 inches, or L
  • 0.50 inches, or H
  • 0.875 inches, or XH
  • 1.125 inches, or XXH
  • 0.0816 inches, or LT
  • 2.0 millimeters, or T2 and AT2
  • 2.5 millimeters, or T2.5 and AT2.5
  • 5.0 millimeters, or T5 and AT5
  • 10.0 millimeters, or T10 and AT10

The type of material that is available will largely depend on the size of the profile that you're working with. L, H, and XH can be created using neoprene with fiberglass, for example. Anything with a "T" or “AT” designation is commonly offered in urethane with steel reinforcements.


The next most common type of timing belt tooth profile is called the curvilinear profile. These were designed for applications that require high torque and high speeds in particular. In these precise use cases, they are considered to be a definite upgrade over their trapezoidal counterparts. They offer better tracking capabilities, all while being known for fewer instances of backlash.

Curvilinear profiles include HTD® profiles with the following measurements:

  • 3 millimeters
  • 5 millimeters
  • 8 millimeters
  • 14 millimeters

Although this will obviously vary depending on the project you're talking about, most of these curvilinear timing belt tooth profiles are available in neoprene with fiberglass reinforcements.

Modified Curvilinear

Modified curvilinear profiles, as the term implies, are intended to continue to improve on standard curvilinear options. These profiles are known for a smaller tooth depth that, coupled with a greater flank angle, give it the highest torque and force transmitting capabilities available. Having said all of that, they might be considered "overkill" in situations that don't call for this type of design advantage.

What is interesting about modified curvilinear profiles is that the area between one tooth and the next is what shares the load with the teeth themselves. Because of this, timing belts that are equipped with this type of tooth profile are less likely to have problems like ratcheting, even when you're pushing the system to the limit as far as the load is concerned.

Choosing the Right Profile

Again, the profile that you select should ultimately be dictated on the requirements of the project you're working on.

The precise nature of the trapezoidal belt profile results in higher stress concentrations, for example. If used in an application where torque and/or speed are very high, this could lead to high wear rates - meaning that you would want to use one of the other two options in this instance.

Curvilinear profiles are great for cutting down on issues like belt ratcheting, but they also have higher backlash. If you know that your application requires exceptionally high torque and speeds, modified curvilinear tooth profiles would be the way you should go.

None of this is to say that one tooth profile is inherently better than the others - it's just that each one is better in its own specific context.

It's also important to note that even if you're looking at two timing belts that appear to have the same basic tooth profile and the same tooth pitch, they still might not be interchangeable with one another. There are a myriad of other variations that are at play, including the dimensions between the designs, the product line you're working with, and more.

That's ultimately why it's so important to partner with an organization like Illinois Pulley & Gear on all your replacement part needs. We'll collect all relevant information to make sure you walk away with parts you can use and depend on, no matter what.

IPG is Here to Help!

At Illinois Pulley & Gear, we pride ourselves on our ability to deliver precision pulleys done right. In addition to timing belts and related equipment, we have over 90 years of experience offering industry leading manufacturing solutions that are designed with our customers needs in mind. We value honesty, hard work, and responsibility above all else - which is why we won't rest until we have parts that meet your needs and exceed your expectations.

So whether you're interested in timing pulley stock, timing pulleys, gears, or something else entirely, your partners at IPG will proudly stand by your side every step of the way.

If you'd like to find out more information about how to choose the right timing belt tooth profile, or if you'd like to talk to someone about your own manufacturing needs in a bit more detail, please don't hesitate to contact us today.