SpiritR
02-18-2008, 08:26 AM
http://fdowners.com/images/unsprung-mass-car-diagram.jpg
The unsprung mass is the mass of the suspension, wheels and other
components directly connected to them, rather than supported by the suspension.
(The mass of the body and other components supported by the suspension is the sprung mass.)
Unsprung mass includes the mass of components such as the wheel spindles, wheel bearings,
tyres, and a portion of the weight of driveshafts, springs, shock absorbers, suspension links
and the vehicle's disc brakes.
Effects of Unsprung Mass
The unsprung weight of a wheel controls a trade-off between a wheel's
bump-following ability and its vibration isolation. Bumps and surface imperfections
in the road cause tyre compression--which induces a force on
the unsprung weight. In time, the unsprung weight then responds to this
force with movement of its own. The amount of movement is inversely
proportional to the weight - a lighter wheel which readily moves in response
to road bumps will have more grip when tracking over an imperfect road.
For this reason, lighter wheels are often sought for high-performance applications.
In contrast, a heavier wheel which moves less will not absorb as much vibration;
the irregularities of the road surface will transfer to the cabin through the geometry
of the suspension and hence ride quality is deteriorated.
Short Version is Unsprung mass moves when the wheel moves.
Sprung mass moves when the chassis moves.
For example much a larger brake kit that is substantially heavier
could contribute enough to the unsprung mass of the vehicle to
upset native balance.
Those that have radically altered their wheel area please share.
The unsprung mass is the mass of the suspension, wheels and other
components directly connected to them, rather than supported by the suspension.
(The mass of the body and other components supported by the suspension is the sprung mass.)
Unsprung mass includes the mass of components such as the wheel spindles, wheel bearings,
tyres, and a portion of the weight of driveshafts, springs, shock absorbers, suspension links
and the vehicle's disc brakes.
Effects of Unsprung Mass
The unsprung weight of a wheel controls a trade-off between a wheel's
bump-following ability and its vibration isolation. Bumps and surface imperfections
in the road cause tyre compression--which induces a force on
the unsprung weight. In time, the unsprung weight then responds to this
force with movement of its own. The amount of movement is inversely
proportional to the weight - a lighter wheel which readily moves in response
to road bumps will have more grip when tracking over an imperfect road.
For this reason, lighter wheels are often sought for high-performance applications.
In contrast, a heavier wheel which moves less will not absorb as much vibration;
the irregularities of the road surface will transfer to the cabin through the geometry
of the suspension and hence ride quality is deteriorated.
Short Version is Unsprung mass moves when the wheel moves.
Sprung mass moves when the chassis moves.
For example much a larger brake kit that is substantially heavier
could contribute enough to the unsprung mass of the vehicle to
upset native balance.
Those that have radically altered their wheel area please share.