Idler pulleys, which are used for example to calm critical belt sections, prevent collision problems with the adjacent components, guide the belt or increase the wrap angle at adjacent pulleys, must fulfill the same requirements as belt tensioning systems in relation to service life and noise generation. For this application, high precision single row ball bearings with an increased grease reservoir have proved effective; double row angular contact ball bearings, also with an optimised grease reservoir, are also used if appropriate. These bearings have high temperature rolling bearing greases and appropriate sealing rings; standard catalogue bearings are less suitable for this application. Depending on the requirements, these bearings are fitted with pulleys made from plastic or steel.
The pulleys made from polyamide resistant to high temperatures are, due to the highly developed tooling and production technology, equal in terms of roundness and running characteristics to the steel pulleys used as an alternative.