On Sat, 11 Jan 1997 11:34:07 -0800
Ross MacPherson <arm@unix.infoserve.net> asked:
> Could someone explain to me the pros and cons of "sprung" vs. "unsprung
> weight" ? I know what the terms mean but I don't understand the effects on
> performance.
According to Fred Puhn (How To Make Your Car Handle), Sprung Weight
is the weight of the chassis and all parts mounted on the chassis.
Unsprung Weight includes all the moving suspension parts. Performance
for a road car is maximized when both are as light as possible, but
the ratio of sprung to unsprung weights is of paramount importance on
a bumpy road. A ratio of 5 is good and 2 is bad. With less unsprung
weight, the car will accelerate faster and stop faster, for a given
horsepower. With less sprung weight, the springs and dampers can more
easily and quickly react to movement of the tires caused by an
irregular road surfaces. The ratio of the two determines how much of
the movement of the suspension is transmitted to the body of the car,
and its occupants. The inertia of the relatively heavy body resists
the movement of the lighter suspension, so keeps the tires pressed
into reasonably firm contact with a bumpy road surface. The most
noticeable result is a smoother ride, but cornering, acceleration, and
braking traction on bumps are improved as well by a higher ratio.
Condensing a page or so of Mr. Puhn to a paragraph, is a bit
confusing, but I hope makes at least some sense. Just remember,
lighter is better, and if it moves, lightest is best. An acronym for
that is LOTUS.
Jerry Causey - 1967 MGB GT
Whidbey Island, Washington, embraced by the Puget Sound
(fairly close to Seattle, and the rest of the USA)
|