Originally Posted by CarbonJoe
Another way of saying place the car on the edge of the table, with either both fronts or both rears off the table. You're using the edge of the table as the pivot point. Lower the side that is hanging off the table, and watch to see if both tires lift off the table at the same time.
That's more checking that the droop is equal, but there are more precise ways of doing that.
The compression being equal is what is usually checked by this method.
With the rear wheels only on the table, front tires off the table (chassis 90 degrees to the edge of the table), lift the front of the car straight up from the very center and watch how the rear compresses. If one side drops quicker than the other, add a bit of preload to that side and remove a little from the other. Keep doing that until the car compresses equally. Then turn the car around and check the front.
Get the car left/right weight balanced before doing any of this.
If you hear someone say "square up the car" they are usually referring to this method of making sure the shocks compress equally.