Timing Belts and Pulleys

Timing Belt and Pulley Basics

The Timing Belt and Pulley system is a pulley-based motion transmission system. Timing Belts and Pulleys transmit motion similarly to sprockets and chains. Both the Belt and the Pulley have teeth that interlock and engage with each other to drive motion.

Timing Belts and Pulleys are lighter, more compact, and more efficient at transferring motion than chain and sprockets. Belts do not stretch over time as much as chain, making re-tensioning less of an issue. In general, a timing belt and pulley system should last a full season, if properly installed. Follow through the rest of this section to learn more about proper installation and tensioning of the REV GT2 3mm Pitch Pulley and Belt system.

Product Specs:

The REV GT2 3mm Pitch Pulleys and the GT2 3mm Pitch Belt come in various sizes to fit your needs.


GT2 3mm


Acetal (POM)



All pulleys, except the 12 Tooth (REV-41-1668), come with two ends and an inset to adjust the width of the pulley as needed to drive multiple belts.

Belt Installation

All of the GT2 3mm Pitch Pulleys, with the exception of the 12 Tooth Pulley, have flanges to keep the belt on track. This is because the belts tend to thrust to the side when in motion. It is recommended that at least one pulley in the system have flanges to keep the belt from slipping. In situations where the center distance between shafts is more than 8 times the diameter of the smaller pulley or when the drive is operating on vertical shafts, both pulleys should have flanges on both sides.

When choosing what structural aspect to use to support a pulley system it is important that the support be rigid or capable of withstanding torsion. Any significant flex or give in the supporting structure can cause the center to center distance between the pulleys to change. Repercussions to a change in center distance are: slack in the belt and the belt jumping teeth.

During the installation process, ensure that supporting shafts are parallel and that pulleys are aligned.

Belts require relatively little maintenance if installed correctly but its always advised to run the center distance calculation to account for installation and removal of belts.

As a general rule avoid subjecting belts to sharp bends or rough handling.

Belt Tension

The Timing Belt when installed should be snug, to ensure a longer life and less wear on the mechanism. A taut belt is not going to have the same lifespan as a snug belt and a loose belt may jump teeth in situations where torque is high.

When working with the REV GT2 3mm Pitch Pulleys and Belts there will be some difference in pitch between the Extended Motion Pattern, featured on the Channels, and the pitch of the Timing Belts. Because of the mismatched pitches, there may be limitations to the getting the perfect center to center distance. One solution to accommodate for this issue is to use a combination of M3 Standoffs (REV-41-1492) and Tensioning Bushings (REV-41-1702) to help tension the belt appropriately.

Do not force the belt over the flange of the pulley!