I picked up some cast wheels awhile ago to replace my spoked wheels.I weight them the other day to see the difference,the spoked rear wheel is 42 lbs. and the cast is 34.5 lbs. that's with rotor attached on both.I might feel a difference when pulling away from a traffic light due to unsprung weight.

Actually, what you're talking about is rotating mass, not unsprung weight. Rotating mass must be accelerated/decelerated every time the speed changes, and it's harder to accelerate the rotating mass. Since most rotating mass (aside from the engine and the tranny) is unsprung weight (wheels, brake rotors), a reduction in unsprung weight generally entails a reduction in rotating mass, which helps acceleration. It is rotating mass that is roughly 3 times harder to accelerate than normal weight. Plain old unsprung weight is not any harder to accelerate. Basically, rotating mass must be accelerated twice every time the car speeds up, it must be accelerated linearly (in the direction of the vehicle's travel) and rotationally (in the direction of its spin).

As for a reduction in unsprung weight independant from rotating mass, this generally improves the suspension's ability to work properly. Unsprung weight contributes to inertia in the suspension, which in turn affects the geometry assumed by the suspension.

BikerRon wrote:
Actually, what you're talking about is rotating mass, not unsprung weight. Rotating mass must be accelerated/decelerated every time the speed changes, and it's harder to accelerate the rotating mass. Since most rotating mass (aside from the engine and the tranny) is unsprung weight (wheels, brake rotors), a reduction in unsprung weight generally entails a reduction in rotating mass, which helps acceleration. It is rotating mass that is roughly 3 times harder to accelerate than normal weight. Plain old unsprung weight is not any harder to accelerate. Basically, rotating mass must be accelerated twice every time the car speeds up, it must be accelerated linearly (in the direction of the vehicle's travel) and rotationally (in the direction of its spin).

As for a reduction in unsprung weight independant from rotating mass, this generally improves the suspension's ability to work properly. Unsprung weight contributes to inertia in the suspension, which in turn affects the geometry assumed by the suspension.

OK so I used the wrong terminology,but I know what I meant.But its good to let everyone else know what I was trying to say.

ondaroad wrote:
BikerRon wrote:
Actually, what you're talking about is rotating mass, not unsprung weight. Rotating mass must be accelerated/decelerated every time the speed changes, and it's harder to accelerate the rotating mass. Since most rotating mass (aside from the engine and the tranny) is unsprung weight (wheels, brake rotors), a reduction in unsprung weight generally entails a reduction in rotating mass, which helps acceleration. It is rotating mass that is roughly 3 times harder to accelerate than normal weight. Plain old unsprung weight is not any harder to accelerate. Basically, rotating mass must be accelerated twice every time the car speeds up, it must be accelerated linearly (in the direction of the vehicle's travel) and rotationally (in the direction of its spin).

As for a reduction in unsprung weight independant from rotating mass, this generally improves the suspension's ability to work properly. Unsprung weight contributes to inertia in the suspension, which in turn affects the geometry assumed by the suspension.

OK so I used the wrong terminology,but I know what I meant.But its good to let everyone else know what I was trying to say.Yup, I get it,The more stuff we add to our bikes the slower they get

roadiemort wrote:
Yup, I get it,The more stuff we add to our bikes the slower they get

Yeppers, it may take longer for us to get there, but we get there in Comfort and Style.

If you put air in them tires do they get lighter ? LOL

ondaroad wrote:
I picked up some cast wheels awhile ago to replace my spoked wheels.I weight them the other day to see the difference,the spoked rear wheel is 42 lbs. and the cast is 34.5 lbs. that's with rotor attached on both.I might feel a difference when pulling away from a traffic light due to unsprung weight.

What tires were mounted? Tire weight can vary as much as 6 pounds from one manufacturer to another.

roadiemort wrote:
ondaroad wrote:
BikerRon wrote:
Actually, what you're talking about is rotating mass, not unsprung weight. Rotating mass must be accelerated/decelerated every time the speed changes, and it's harder to accelerate the rotating mass. Since most rotating mass (aside from the engine and the tranny) is unsprung weight (wheels, brake rotors), a reduction in unsprung weight generally entails a reduction in rotating mass, which helps acceleration. It is rotating mass that is roughly 3 times harder to accelerate than normal weight. Plain old unsprung weight is not any harder to accelerate. Basically, rotating mass must be accelerated twice every time the car speeds up, it must be accelerated linearly (in the direction of the vehicle's travel) and rotationally (in the direction of its spin).

As for a reduction in unsprung weight independant from rotating mass, this generally improves the suspension's ability to work properly. Unsprung weight contributes to inertia in the suspension, which in turn affects the geometry assumed by the suspension.

OK so I used the wrong terminology,but I know what I meant.But its good to let everyone else know what I was trying to say.Yup, I get it,The more stuff we add to our bikes the slower they get

thats why I keep taking stuff off......