Flywheel lightening

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Apart from being a handy place to fit a clutch and starter ring gear, the flywheel’s primary function is to smooth out the transmission of power from the crankshaft and for this you require mass (weight). The problem here is that this weight acts as a resistance to, as well as a store for, the energy produced by the engine. Lightening the flywheel will improve the engine’s response to throttle openings but not the actual power output. Unless the flywheel is abnormally heavy we do not recommend flywheel lightening for road stages of tune. The slight loss of low speed torque and flexibility resulting from the tuning modifications carried out, can be greatly exacerbated by a lightweight flywheel. However, for all serious tuning a lightweight flywheel is essential. Standard cast iron flywheels can be lightened but there is always a risk of them exploding if too much material is removed from critical areas. The rule here is not to be over-ambitious when machining weight from a standard flywheel - it isn’t worth the risk! The safe answer is to buy a steel flywheel which are available for most popular engine / clutch formats. The final point on flywheels is to make sure it is firmly secured to the crankshaft. Always fit new HT bolts and always double check that they have been torqued correctly. If engine speeds in excess of 7500rpm are anticipated then, wherever possible, the flywheel and crankshaft should also be double dowelled for extra security.

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