determining "sprung mass"

orange150

orange150

Well-Known Member
Joined
Mar 20, 2005
Location
Fairfax City, VA
so researching what "sprung mass" is i found that it is the mass above the springs (and anything below is unsprung mass) so how do you go about determining what your "sprung mass" is.

all this is for that dern 4-link calc by the way
thanks
 
best you can do without big scales and taking stuff apart is estimating it. take your gvw and subtract your stock axle/wheel weights and anything else you've removed above the springs (bed for instance). you'll also need to account for the heavier items you've added above the springs, such as the 205 case, front crossmember, etc...
 
Run by a CAT scales...available at most truck stops...will cost anywhere between $8-$25. Then start figuring out your subtractable weight...Wheels and tires are easy, throw one on th bathroom scale and multiply by 4. Somewhere on the net you can get the weight of your axles. Spring supplier will know the shipping weight of your springs...or what a similar sized spring would be. I wonder how you would count a driveshaft?
 
You really need to put the fawker on a scale.... especially in order to find the CoG. You can make do without knowing it, but in the end you're making guesses based on assumed values and estimates.

Isn't it about time to put that thing together and learn how to drive it? You'll graduate from school first at this rate. :flipoff2:
 
There was a procedure to find CoG that involved picking the front of the truck up with the back tires on scales, blah blah... Gonna have to do that eventually for mine. (or, I wonder if the balance beam game could also suffice?)

For shocks, springs and driveshafts, generally accepted is to use 1/2 the weight as unsprung.
 
How accurate should he be in that calculation, and which direction should he err in? I would suspect it's better to be a little overweight because of fuel, tools, passengers, food, camping gear, etc.

Basically, I'm asking if an educated guess gets him into the right ball park for these calculations, or do they need to be fairly precise?

J
 
How predictable do you want the results to be?

I'd say that from a strictly academic point of view, you'd want to weigh the truck as it would be outfitted and driven 90% of the time.... whether that's in trail trim, daily driver trim, whatever. You don't want to load the bed with 500# of sakrete any more than you want to weigh it stripped with no motor and an empty tank.

But within a certain range, it's not really going to matter. One occupant? Two? None? Probably not going to make a difference.
 
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