[Luddite]

Originally Posted by Darkness

I was hoping someone had done the maths on costs and comparative effects of losing 1Kg from the flywheel, rear sprocket, and back wheel & tyre?

There's a very simplified calculation ('force = mass x acceleration') in the Ducati Up North article on lightened flywheels http://www.ducati-upnorth.com/tech/flywheel.php which also touches on the benefits of lighter road wheels.

Here's an extract:

"When you remove weight from the flywheel (and to a lesser degree, from the clutch) the effect on the engine’s ability to more quickly spin-up is indistinguishable from increasing your engine’s torque (and consequently horsepower) output.

But only in neutral. In any other gear, there’s little benefit at all.

Obviously, your bike’s ability to accelerate faster through the gears is enhanced by reducing the overall weight of the bike as well as the inertia of rotating components. The crankshaft, pistons and connecting rods, transmission gears, drive chain and sprockets, wheels and tires, clutch and flywheel are all candidates.

However, the overall weight of the bike and rider completely overwhelms any reduction of rotational inertia produced by a lighter flywheel. A kilogram lighter flywheel on a 300 kilogram bike-plus-rider will accelerate only 0.3% faster. F=ma.

Of course every 0.3% helps a racebike. When you reduce weight you’ll get faster acceleration, and faster lap times - IF - you can modulate your wheel spin driving out of corners. Factory racebikes make so much power, for example, that transmitting the power to the road effectively becomes the limiting factor - so heavier flywheels actually become a benefit. Fear the high-side."