Drive belts should be inspected and changed regularly to avoid further complications. We offer Genuine BMW and other aftermarket brands that we trust or know to be OE manufacturers. We like to make it easy on you and do all the research for you - check out our Drive Belt Service kits.
This is an OEM Febi Upper Idler Pulley, also known as the roller pulley or deflection pulley. The upper and lower idler pulleys are known to be the primary sources for 'belt squealing'. The pulley is also encased in rubber which will crack over time. If left without service the rubber could fail completely, chucking the belt and leaving you stranded. Replacement is a very simple procedure and can be done anytime the fan is off the engine (belt replacement, water pump service, alternator replacement, etc).
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Every time the cylinders fire, torque is transferred into the crankshaft. The crankshaft deflects under this torque, which sets up vibrations when the torque is released. At certain engine speeds the torque imparted by the cylinders are in sync with the vibrations in the crankshaft, which results in a phenomenon called resonance This resonance causes stress beyond what the crankshaft can withstand, resulting in crankshaft failure. The accessory pulley acts as a balancer and prevents these vibrations from destroying your crankshaft.
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