Posted October 12, 2012 - 06:54 AM
Is the Steahly actually listed as 9 ounces up on a stock '11?
The reason that the GYT-R is "only" 4.4 ounces heavier than stock, while their off-road flywheel for the '06-'09 is +9 ounces, is that the EFI flywheel is much larger than the older ones. That means that weight placed at the outer edge will have a vastly greater effect on rotating inertia than the same weight placed on a smaller one. Looking at the GYT-R flywheels for both, the 9+ oz. weight added to the '08 'wheel resulted in raising the inertia mass of the flywheel from 3.8 to 6.15 kg/cm². The weighted flywheel for the '11 has an inertia mass of 9.2 kg/cm².
Another question is whether the Steahly is a built flywheel with a ring welded to the outside diameter as the GYT-R products are, or is it done with a weight in the form of a disc that bolts or otherwise fastens to the center of the original flywheel, as Steahly so often did with the older units. Much of the mass of a disc is located near its center, and the closer to the center of a rotating device the weight is, the slower it will move, and the less it will affect inertia.
I'm a fan of big flywheels, particularly for how they enhance engine power at very low speeds, and for the improvement to traction, but IF the 9 ounce Steahly product is done with a ring around the outside like the GYT-R unit, I might wonder about that being heavier than I'd like. Then again, the big ol' flywheel on the WR works out just fine.