Timing belt deflection pulley - an auxiliary component of the timing belt drive, providing the necessary belt tension for normal operation of the drive. Additionally, this device can act as a bypass roller.

The timing belt drive is sensitive to belt tension. Excessive tension leads to intensive wear of the timing parts - pulley bearings (water pump, generator, tensioner, etc.), the belt itself and others. In addition, a tight belt stretches faster and shortens its service life. Too little preload is fraught with more serious problems - slipping of the belt along the toothed pulleys of the camshafts, which leads to a violation of the valve timing and deterioration of the entire engine.

Therefore, a tensioning device is introduced into the timing drive in the form of rollers of one design or another, which, during engine operation, maintain an optimal belt tension.

1. POLO (6N1)
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The construction of the FEBI BILSTEIN brand Deflection/Guide Pulley, timing belt

Deflection pulley - a plastic or metal pulley with a smooth surface mounted on a single or double row deep groove ball bearing. The roller rests against the back of the belt, and when the engine is running, it rotates freely under the action of the belt running along it. The rollers can be smooth or have a shoulder (s) to prevent the belt from shifting.