CHARACTERISTICS OF A NOISY DRIVE
Belt Noise is a common “symptom” in many belt drive applications. The following are variables of the accessory drive that can increase the risk of belt noise:
1. DRIVE LAYOUT/DESIGN
• Most problem drives typically have a short belt span between a backside pulley and a grooved pulley. If misaligned enough (typically 1° or more), a belt chirp noise will almost always occur as the short span enters the grooved pulley.
• Due to the increased loads of accessories that are being demanded, sufficient pulley wraps and belt tensions are critical to insure that belt slippage does not occur, which results in belt noise.
2. ACCESSORY VARIATION
• Many aftermarket suppliers do not provide the same tight tolerances (and dimensions) as required by the OE manufacturer on accessory mounting location to pulley centerline. This accessory variation can cause unacceptable drive misalignment, which results in belt noise.
3. ACCESSORY/PULLEY CONDITION
• Worn pulley surfaces, locked-up or tight bearings, and/or worn-out bearings causing high run-out / free-rock conditions can cause belt noise.
4. AMBIENT WEATHER CONDITIONS/ENVIRONMENT/CONTAMINATION
• Cool temperatures with high humidity, or very cold temperatures (<0°C) will increase the likelihood of misalignment chirp to occur.
• Sandy/Rocky drive conditions can cause small stones to lodge into the belt ribs, which can cause a grinding/ticking noise in the accessory drive.
• Most all engine fluids (oil, antifreeze, P/S fluid, …) that are spilled onto the belt, as well as belt dressings that are applied to the belt can cause the belt to make noise.
5. BELT CONDITION
• A belt that is not within specification for rib angles, rib pitch, etc..., an extremely worn belt with no fiber on the rib flanks, and/or a belt that is too long or too short can increase the risk of belt noise.
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