Most factory or OE flywheels are made from cast iron (a.k.a. gray iron) to keep costs down. Cast iron is a very heavy and porous material and can be brittle when subjected to high stress loads. Steel is an alloy of iron where carbon has been added to increase strength and make the material more resistant to cracking.
The choice between steel and aluminum performance flywheels is mainly a function of the vehicle’s planned uses and driver preferences. Either type of flywheel is a viable choice and improvement over cast OE units depending on what you are looking for in strength and performance, what type of vehicle you have and how you will be using it… Steel flywheels are designed to be stronger than OE ones and will deliver approximately the same weight (or in some cases more) than OE cast iron or nodular flywheels. This means they will deliver about the same inertia at rpm and driving characteristics as the OE unit, but will be less likely to break or explode under high rpm, high load conditions as seen in drag racing, etc. Steel flywheels are often SFI approved for race use. Steel flywheels are also a good choice for helping move heavy vehicles at lower rpms, such as in heavier trucks and for rock crawling, hill climb, etc. These flywheels are designed for use where extreme strength is the issue and not increased performance. Other considerations with steel flywheels are that they still require resurfacing when changing clutches and therefore have a limited service life, requiring eventual replacement, and that they do nothing to improve heat dissipation from performance clutches and therefore can not significantly improve clutch performance or longevity. Another drawback is that the ring gear teeth are often cut right into the steel flywheel, meaning any damage to even a few teeth from a starter mishap, etc. will often mean replacing the entire flywheel.
Billet aluminum flywheels are also designed to be much stronger than OE cast iron flywheels, but their lower weight will provide significant performance benefits by delivering faster throttle response, quicker acceleration, smoother shifting, easier vehicle braking and by freeing up additional horsepower to the wheels (by reducing parasitic driveline loses). Billet aluminum flywheels can also deliver OE equivalent inertia, but at increased rpms, and will require a slightly modified driving style. Billet aluminum flywheel equipped vehicles will provide a more responsive and “nimble” driving experience over vehicles equipped with heavy iron or steel flywheels. All Fidanza Performance aluminum flywheels are made from high quality 6061 T6 billet aluminum to deliver the optimum in strength and durability and are often SFI approved for race use just like steel flywheels. Our billet aluminum flywheels are a great choice for street performance vehicles, as well as, ones used in road racing, autocross, time attack, drift and drag racing; anyplace where increased horsepower and throttle response is desired. In addition, aluminum flywheels are much better at dissipating heat from your clutch, which can greatly improve clutch performance and life; and all Fidanza Performance aluminum flywheels feature a replaceable hardened steel clutch friction surface, which means they are infinitely re-buildable and will deliver years and years of exciting drivability.