Mopar Muscle Association UK

Is a spring sprung weight or unsprung weight or is it a mixture of sprung and unsprung?

The spring is unsprung weight,everything after the spring eyes.

For dynamic calculations I take half the mass of the spring and count it as unsprung, the other half is obviously sprung. In reality you should calculate how much of the mass of the spring actually acts on the sprung and unsprung sides but it a a long winded and pointless excercise.

You should also do the same for other components such as the wishbones.

Kev wrote:Is a spring sprung weight or unsprung weight or is it a mixture of sprung and unsprung?

It depends!
A torsion bar is not part of the unsprung weight, coil springs do add to unsprung weight - another advantage of torsion bars!!

Generally I thought that springs were part sprung, part unsprung - but that is from memory, could be wrong.....

I always thought of leaf and coil springs as being unsprung weight. Mopar torsion bars as sprung. The reason being it makes it easier when working out what spring rates you need.

If this is about Mopars then remember these are not light weight racers. They are two tons of Yank iron.

At the rear the axle and wheels make up most of the unsprung weight anyway. The mass of the leaf springs adds to that and the percentage left over makes little difference to the calculations on cars this big and heavy.

Trust me. I spent a lot of time working out my rear spring specifications without any previous knowlege of how to go about it. In the end you have to make an educated guess about some bits. And no matter how well you do the sums you will still not be spot on. You will still need to make adjustments to the set-up.

So why get that far into it? Unless you are developing a F1 car forget about it.

Why make a mountain outa a molehill..............Unsprung weight is where the springs are at rest & sprung weight is when they have a load on them

Unsprung weight takin into account the axle,wheels etc etc.

Sprung weight is axle plus body

"Suspension control devices, such as shock absorbers, control arms, brake struts, some stabilizer bars, tie rods, and springs, have one end sprung and the other end unsprung. Their weight is usually considered to be sprung weight."
So it says in a book called "Automotive Suspension, Steering, and Brakes" 1980 Prentice-Hall.

The suspension masses comprise the mass of the wheels and the wheel carriers. The latter can be the steering knuckles or, in the case of rigid axles, the axle housing including the differential. There is also the proportional (sometimes half) mass of the suspension parts, which flexibly connect the actual axle with the body or frame. This includes:

• Suspension Control Arms
  Tie Rods
  Axle Shafts
  Leaf or Coil Springs
  Shock Absorbers
  Anti Roll Bar Arms
  Panhard Rod etc

The other half of the mass is accounted for by the body. Torsion bars are in the underbody, so their mass forms part of the sprung mass.

Extract from "The Automotive Chassis, Engineering Principles" (Second Edition) by J.Reimpell, H.Stoll and J.W.Betzler (an excellent method of getting to sleep, or analysing suspension systems!).

Only hope you lot don't follow the destructions when settin up the video