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> Tires, wheels, and suspension parts are considered unsprung weight.
> Everything else is sprung weight. The ratio of sprung to unsprung
weight
> has an important effect on the handling of a car on bumpy surfaces,
and
> is a factor in automobile design. A ratio of 5 is good and a ratio of
2
> is very poor.
>
> A car with a high sprung-to-unsprung weight ratio will stick better on
> bumpy roads than a car with a lower ratio. The car will also ride
> better. The reason is, the heavy body of the car is not disturbed much
> by the relatively light wheels and suspension parts parts bouncing up
> and down. The inertia of the body resists the movement of the tires,
and
> thus the tire is pressed into resonably firm contact with a bumpy road
> surface.
>
> You can get this effect by ading a heavy load to your car. The ride
will
> usually be noticeably smoother, particularly on a washboard surface.
The
> cornering and acceleration or braking traction on bumps is improved
too.
> Up to a point, as long as the suspension doesn't begin to bottom. And
> adding weight will, of course, decrease acceleration -- same power,
more
> mass to move.
>
> To get better handling on bumps, it is much better to reduce unsprung
> weight and keep the sprung weight as light as possible. To think of it
> in another way, the lighter the car, the less sophistication is
required
> in the suspension to provide decent handling.
>
> Midgets handle better than 'B's, all things being equal, because the
> amount of sprung weight (the car) is a lot less while the unsprung
> weight (the suspension) is nearly the same. The ratio of sprung to
> unsprung weight goes up; the car seems more throwable in the corners.
> With significant weight loss and just a slight decrease in horespower,
> the Midget will seem as quick (and in some case is quicker) than the
'B'
> roadster.
>
> Finally, all things being equal, the B/GT may seem to be a more
> comfortale tourer because it has more weight, thus again raising the
> sprung-to-unsprung weight ratio, although, at the limits of handling,
> and with the same horsepower, it will not perform as well.
>
<<snip>>
>
> Bob Allen, Kansas City, '69CGT, '75TR6
Bob,
Your post made sense, with one exception. How could the
sprung-to-unsprung ratio go UP for the midget, if it has a much lighter
body, and approximately the same upsprung weight (suspension)?
It should have gone down. This should be obvious, since the ratio does
in fact go up for the MGB-GT, because it is HEAVIER, with approximately
the same suspension.
Also, I have never heard of the 5:1 and 2:1 breaking points for
"good" and "bad" before. Considering the only unsprung components are
wheels, tires, brakes, shocks and possibly the springs themselves, I
can't imagine the car that wouldn't have at LEAST a 5:1 sprung/unsprung
ratio.
Thanks for the good input. I think it just boils down to less being
better when it comes to unsprung weight.
Scott Gardner
'72 MGB
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<DT> > <BR>
> Tires, wheels, and suspension parts are considered unsprung weight.<BR>
> Everything else is sprung weight. The ratio of sprung to unsprung
weight<BR>
> has an important effect on the handling of a car on bumpy surfaces,
and<BR>
> is a factor in automobile design. A ratio of 5 is good and a ratio
of 2<BR>
> is very poor.<BR>
> <BR>
> A car with a high sprung-to-unsprung weight ratio will stick better
on<BR>
> bumpy roads than a car with a lower ratio. The car will also ride<BR>
> better. The reason is, the heavy body of the car is not disturbed
much<BR>
> by the relatively light wheels and suspension parts parts bouncing
up<BR>
> and down. The inertia of the body resists the movement of the tires,
and<BR>
> thus the tire is pressed into resonably firm contact with a bumpy
road<BR>
> surface.<BR>
> <BR>
> You can get this effect by ading a heavy load to your car. The ride
will<BR>
> usually be noticeably smoother, particularly on a washboard surface.
The<BR>
> cornering and acceleration or braking traction on bumps is improved
too.<BR>
> Up to a point, as long as the suspension doesn't begin to bottom.
And<BR>
> adding weight will, of course, decrease acceleration -- same power,
more<BR>
> mass to move.<BR>
> <BR>
> To get better handling on bumps, it is much better to reduce unsprung<BR>
> weight and keep the sprung weight as light as possible. To think of
it<BR>
> in another way, the lighter the car, the less sophistication is
required<BR>
> in the suspension to provide decent handling.<BR>
> <BR>
> Midgets handle better than 'B's, all things being equal, because the<BR>
> amount of sprung weight (the car) is a lot less while the unsprung<BR>
> weight (the suspension) is nearly the same. The ratio of sprung to<BR>
> unsprung weight goes up; the car seems more throwable in the corners.<BR>
> With significant weight loss and just a slight decrease in horespower,<BR>
> the Midget will seem as quick (and in some case is quicker) than the
'B'<BR>
> roadster.<BR>
> <BR>
> Finally, all things being equal, the B/GT may seem to be a more<BR>
> comfortale tourer because it has more weight, thus again raising the<BR>
> sprung-to-unsprung weight ratio, although, at the limits of handling,<BR>
> and with the same horsepower, it will not perform as well.<BR>
> <BR>
<<snip>><BR>
> <BR>
> Bob Allen, Kansas City, '69CGT, '75TR6<BR>
<BR></DT>
<DT>Bob,</DT>
<DT> Your post made sense, with one exception. How could the
sprung-to-unsprung ratio go UP for the midget, if it has a much lighter
body, and approximately the same upsprung weight (suspension)?</DT>
<DT>It should have gone down. This should be obvious, since the ratio
does in fact go up for the MGB-GT, because it is HEAVIER, with approximately
the same suspension.</DT>
<DT> Also, I have never heard of the 5:1 and 2:1 breaking
points for "good" and "bad" before. Considering
the only unsprung components are wheels, tires, brakes, shocks and possibly
the springs themselves, I can't imagine the car that wouldn't have at LEAST
a 5:1 sprung/unsprung ratio.</DT>
<DT> </DT>
<DT> Thanks for the good input. I think it just
boils down to less being better when it comes to unsprung weight.</DT>
<DT> </DT>
<DT>Scott Gardner</DT>
<DT>'72 MGB</DT>
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