Sprung and Unsprung Weight

Donovan

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I would like to know on a leaf spring truck are the leafs sprung or unsprung weight? Or is it only half that leaf spring weigh considered unsprung? What about driveline, shocks and draglinks? If I weigh all of my componets would that be a better way to get the correct ride height for a set of new custom built leaf springs?

Donovan
 

Dylan

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Any thing that swings and is close to the same cross section along its length like a drive shaft get 1/3 of its mass applied to the unsprung mass. A leaf spring because it has more leaves closer to the axle gets 2/3 of its mass applied to the unsprung. It’s really a lot more complicated than that but its close enough, hope that helps
Dylan
 

Kritter

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Mass or weight?

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ntsqd

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Mass.

TS

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JrSyko

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For us morons, can you explain the difference between sprung and unsprung weight and how it applies? I think I know but not quite 100% sure.

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ntsqd

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partybargepilot has it. think about what is moving as a direct result of a tire hitting a bump. The spring and damper have to counteract this. the less those parts weigh (simplistically: the less mass they have), the easier the job the spring and damper have. OR the faster you can go for the same amount of work that the springs and dampers have to do.

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Chris_Wilson

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Think of 2 baseballs connected with a spring. Hit one the other moves also. Now think of
a baseball attached with a spring to a bowling ball. Hit the baseball and the bowling ball
might move a little but most of the motion is in the baseball. In this analogy, the car is
the bowling ball, the tires (unsprung mass) is the baseball.

This analogy is also good to think about spring rates. The stiffer the spring, the faster
the baseball will oscillate. Or to have the same oscillation rate with a heavier baseball
you also need a heavier spring. Want to upgrade from 35's to 37's? Better look at the
spring rates. And of course the shocks just control the springs or the oscillations.
 
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