Join Date: Feb 2005
Location: Tyee Capital of Canada
Without frame dimensions, you can only check with a tape measure. You need to check for square and parrallesim (sp). It is better if the frame is still attached to the suspension, but if not put the frame level on jackstands. You need to find locations on each side of the frame that match side to side, often there are holes in the fame that were used in manufacturing to position the frame in a jig. You can use crossmember bolt holes or whatever, but there has to be a corresponding hole on each side. With your tape measure from one location on one side to a different location on the other ( the further apart the better) and write down the measurment to within 1/16". Do this several times to ensure you are accurate. Now using the same locations, reverse the measurements side to side, like an × , the two measurements should be the same. If they are not, then the frame is not straight, and it would dogtrack if you used it. Do this check with as many locations as you can.
You can now check the centreline of the frame. Measure the crossmember centres and run a taut string down the centre of the frame, and measure to the frame rails from this centre line, the distance should be the same at each side, for each measurement. If they are not the frame is bent to one side. You may need to drop a plumb bob to the ground from the frame rails and crossmembers if there is obstacles preventing you from getting a line down the centre on top.
To check if the frame is bent up or down, you can use a long carpenters level accross the frame. This should be considered as field measurements only, but will help in identifying a bad frame. If you find what seems to be a good frame, I would still take it to a shop to verify.
How can you trust an atom, they make up everything