TOYOTA 90105-12169 Flywheel Flange Bolt

The TOYOTA 90105-12169 is a genuine-quality, high-tensile flange bolt (flywheel mounting bolt) that plays a critical role in maintaining a secure connection between the engine and the drivetrain. This specially designed fastener secures the flywheel directly to the crankshaft flange, ensuring safe and lossless transmission of engine torque.

Technical Features and Construction

• Integrated Washer (Flanged Design): The integrated flange (washer) optimally and evenly distributes clamping force across the flywheel mounting surface, preventing surface damage and minimizing the risk of vibration-induced loosening.
• High-Tensile Material: Manufactured from premium, heat-treated alloy steel that provides outstanding resistance to continuous shear and tensile stresses, as well as the high thermal loads generated by the engine block.
• Precision Thread Profile: Ensures accurate, uniform torque application during installation, guaranteeing a secure and stable joint.

Function and Importance

Flywheel bolts are among the most heavily stressed fasteners in a motor vehicle. Centrifugal force from the rotating mass, engine vibrations, and abrupt load changes continuously exert stress on the connection. For safety reasons—as most such bolts undergo yield-controlled stretch (stretch bolts) during tightening—it is mandatory to replace the bolts with new ones whenever the flywheel is removed. Reusing old bolts can lead to material fatigue and failure, resulting in catastrophic engine and transmission damage.

Signs of Wear and Damage

• Thread elongation or deformation detected during service work.
• Microscopic cracks at the transition between the bolt head and the shank.
• Corrosion or surface wear on the clamping flange.
• Abnormal vibrations originating from the clutch and flywheel assembly (in case of a loosened joint).