Triumphs Only, Inc. - Triumph Technical Service Bulletin

Flywheel Bolts- Spitfire


October, 1972

A different type of material has been specified for the manufacturing of the flywheel attachment bolts fitted to four-cylinder Triumphs. The change of material affects the tightening torque requirements. Please not that the part number remains unchanged (138526). The new bolt, however, is quite different in appearance and is easily identified.

Bolt Appearance Type Tightening Torque
Black (Parkerized finish) Original 42 to 50 lb./ft.
Bright (Cadmium plated) Revised 35 to 40 lb./ft.

Please advise your workshop personnel of the tightening torque requirements.


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