Good advice so far. I try to stay FAR away from suspension height alteration threads, mainly because all the self-appointed experts on the subject on this forum really don't want to hear from someone who has made his living fixing and/or teaching suspension systems for the past 50+ years. They're smarter than the engineers who designed these old trucks- - -if you don't believe it just ask!
Once suspension systems get beyond simple straight-axle assemblies, changing ride height involves major geometry alterations, and virtually none of them improve a system's performance. Even raising/lowering a straight-axle truck's ride height can produce nasty bump-steer surprises without some serious steering geometry knowledge. When an owner radically raises or lowers a vehicle's ride height the system is put into a situation where what would normally be a momentary set of operating conditions during suspension jounce or rebound becomes the normal operating position. That position will probably produce unwanted thrust vectors and other problems which exaggerate bump steer or Ackerman angles, or produce unpredictable roll responses when an unexpected sharp turn is encountered. A raised or lowered vehicle can be made to track pretty well in a straight line, but handling in turns and the response to bumps can be unpredictable and downright hazardous. Even "lowering spindles" change the scuff radius so that tires are being dragged around a turn instead of pivoting on an imaginary point created by a line drawn through the ball joints and the tread centerline. Combine those angular changes with altered tread centerlines from different-offset wheels to account for wider-than-normal tires, and the geometric relationship of the steering and suspension systems becomes a big guessing game.
Raise or lower the ride height a maximum of 1 inch, and try to stay within the same 1 inch tolerance on wheel center offset, and original alignment angles will work pretty well. Beyond those points, a total re-engineering of the steering and/or suspension would be required for safe, predictable operation. Adjusting caster and camber might get close to proper operation, but there are no guarantees you'll be able to compensate for your modifications. Grafting on a later-model suspension system, with little or no modifications and setting the desired ride height in the process by tweaking the attaching points to the original frame would be the safest method, and will produce the most predictable handling characteristics.
Jerry
Last edited by Hotrod Lincoln; 04/05/2010 7:36 PM.
