How to measure sag?

[Barak]

OK,
bear with me please...
So I have been searching, without success, for an accurate way to measure sag and thus determine if I need new suspension, ( I really "want" new suspension but would like to be able to justify it too).
First Question:
Is there a resource that has the figures for how high a truck with stock suspension sits?

I have seen people measure from the pavement to the bottom of the fenders but different models have different fenders and this method does not take in to account variances in tire pressures.

So today I measured from the bottom of the rim to the bottom of the fender and found the following:
Front right and left are equal at 29 inches (5.5 inches between the "corner" of the tire tread and the bottom of the fender)
Rear left side is low at 28.5 inches
Rear right side is high at 29.25 inches
Second question:
If there is no sag, would all of the measurements be the same? Is this where you would measure sag?

Also, I saw that in the Repair manual under the Front wheel alignment section they show a method of checking vehicle height by measuring (on the rear) the ground clearance to center of rear axle shaft and comparing that to the ground clearance to the lower control arm front bushing center. The axle should sit 1.157 inches higher for my size tire. Any less than that, the rear is lifted and any more than that figure means that there is sag correct? Based on my measurements, it seems my truck is sitting higher - but it sure doesn't look like it.
Third question:
Is this a method also used to measure sag?

My 1996 5 spd V6 SR5 has 170K, has michelin (LTX?) 265/70/16 front Rancho RS5000 struts and rear Rancho shocks and a spring with an orange paint mark (model number undetermined) - Recall has been done on rear springs/damper sometime before purchase. I have had the truck for 4 years and current suspension is what came with it. Lately it seems to be bottoming out more when going over big bumps and even when entering my driveway. Going over small bumps at certain speeds will cause an unpleasant shake/vibration.

Your very experienced suspension thoughts and input would be greatly appreciated.
What a great resource!
Thanks,
Barak
:bravo:

<a href="http://www.flickr.com/photos/30343077@N00/5851557630/" title="IMG_0130 by bnaggan, on Flickr"><img src="http://farm4.static.flickr.com/3096/5851557630_2acdc4dc7f_b.jpg" width="1024" height="765" alt="IMG_0130"></a>

 

[Maritimer]

Look at the cone inside the spring on the rear. That's how much play you have. I was shocked two weeks ago that I had about 2-3 inches riding by myself. With a fully loaded family it was ZERO. :cry2:

Getting new shocks and springs to say the least. :reddance:

 

[Barak]

cones in shock

Look at the cone inside the spring on the rear. That's how much play you have. I was shocked two weeks ago that I had about 2-3 inches riding by myself. With a fully loaded family it was ZERO. :cry2:

Getting new shocks and springs to say the least. :reddance:

space between the cone and the stop - I have less than an inch on the left and a bit more on the right - unloaded
Loaded with a couple of passengers and gear - that gap is closed but i think the spring will still compress all the way to when the rubber stopper meets the axle no? (this is the "new" shorter stopper from the early 4runner recall.)

 

[Maritimer]

My bad. I'm totally new at what things should look like inside and under the truck.

I had the same thing happen to me as far as bumps, so I guess the suspension is shot, which is what the shop said, too. The other thing that is plaguing me is lurch when I brake. It feels like a rickety boat.