Timingriem

Timingriem, commonly referred to as a timing belt, is a flexible toothed belt used in many internal combustion engines to synchronize the rotation of the crankshaft and camshafts. By maintaining precise timing, it ensures valves open and close at the correct moments relative to piston position, and in some designs also drives auxiliary components such as the water pump.

The belt is typically made of reinforced rubber with embedded fibers and a toothed inner surface that mesh with straight or helical pulleys. It is housed under a timing cover and forms part of the engine’s timing system. In interference engines, proper timing is essential to prevent valve-to-piston contact; a slipping belt can cause severe engine damage.

Maintenance and replacement: timing belts have a limited service life. Replacement intervals vary by manufacturer but are commonly around 60,000–100,000 miles (100,000–160,000 kilometers). Many maintenance schedules recommend replacing tensioners, idler pulleys, and, in many engines, the water pump at the same time. Visible signs of wear include cracks, fraying, missing teeth, glazing, or oil contamination; symptoms may include unusual noises, misfires, or rough running.

Compared with timing chains, belts are quieter, lighter, and cheaper to replace but typically require periodic replacement, whereas chains tend to last longer but may require tensioners and guides. Some modern engines use belt-driven camshafts with a chain or belt secondary drive, or switch to a chain entirely for durability. The choice depends on engine design and maintenance philosophy.