How to Identify a Timing Belt

There are several key things that can help you identify a timing belt.

replace timing belt

The ideal situation in determining the details of a timing belt is when the timing belt part number and the name of the belt manufacturer are printed on the timing belt in a legible state.  Many times, the timing belt part number is incomplete or illegible, and the belt manufacturing company either has a timing belt numbering system that isn’t easy to cross reference or is out of business.

The markings on the timing pulleys can determine the profile and pitch of the timing belt, when the timing belt isn’t marked appropriately. The distance from the center of one tooth to the center of the next tooth is called the pitch. A problem arises when it becomes difficult, without proper tooling, to differentiate between several tooth profiles and shapes for 3 mm, 5 mm, 8 mm, and 14 mm pitches. These include the AT5/T5, PowerGrip® HTD/ PowerGrip GT2, Powerhouse™, Powerhouse MX™, and Poly Chain® profiles.

Measuring the overall width and length of the timing belt can easily narrow down your choices in determining the exact pitch and tooth profile of the belt. Counting the cogs or teeth on the timing belt and multiplying it by the pitch can also help measure the timing belt length.

Timing belts come in a variety of materials including neoprene and polyurethane. Neoprene is a usually black and is rather flexible. It is a rubber-like material that can flake after prolonged use. Polyurethane is usually white or clear but can sometimes be black. It is a bit more rigid and slick, especially in larger sizes.

The timing belt part number will look similar to this, once all the details of the belt are located:

640-8MX-12

In the first set of numbers, it usually indicates what the pitch length is for the belt. For this example, the pitch length is 640. In some cases, companies use the first number as the pitch length, usually in MXL pitches. Most companies indicate the number of teeth on the timing belt, so at Toronto Gear Works we adopt the tooth count standard.

In the next set of characters, it indicates the tooth profile and pitch of the timing belt. In this case, it is 8MX. These are the common pitches and profiles we include: MXL (.080"), XL (.200"), L (.375"), H (.500") HTD (3mm, 5mm, and 8mm), Powerhouse™ (2mm, 3mm, 5mm, 8mm, and 14mm), T2.5, T5, T10, AT5, AT10, and Powerhouse MX™ (8mm and 14mm).

For the last set of numbers, the 12 indicates the width of the timing belt. For metric sizes, the number tells how wide the belt is in millimeters. On the standard size however, it indicates the width in inches with a leading zero for sizes that are under an inch: 012=0.125", 025=0.25", 037=0.375", 050=0.500", 075=0.75", 100=1.00", 150=1.50", 200=2.00", and 300=3.00".

In some instances, a letter at the end of the part number will indicate from which material the timing belt is made: UP for Urethane with Polyester reinforcements, G for neoprene with FiberGlass reinforcements, UK for Urethane with Kevlar reinforcements, and US for Urethane with Steel reinforcements. For our example, the timing belt is only offered in Urethane with Kevlar reinforcements so the material code was not added.

Gates®, GT®, Poly Chain®, and PowerGrip® are trademarks of Gates Corporation.

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