Posted by Keith in Washington on Monday, January 09, 2006 at 3:38PM :
In Reply to: Spring Re-arching posted by Dylan Robinson on Monday, January 09, 2006 at 2:50PM :
If you want to lift it higher than stock you need to do more than rearch the springs. If you just rearch the springs beyond stock you actually make the springs shorter in distance from spring eye to eye. This pulls the swing arm of the spring well past the vertical position.
The previous owner of my WC 53 (same springs as a ff PW) rearched the springs to give about 3 1/2" of lift. This resulted in the swing arm being pulled out of vertical so much that it was in direct line with the spring itself. This resulted in the eye of every spring being broken. This is because as the spring flexes it needs to change its length which the swing arm allows. With the swing arm being in direct line with the spring all the spring could do as it lengthened on compression was jam the swing arm into the spring and frame eye bolts. Thankfully the weak point was the spring and they all broke at the eye on my truck.
If you want to lift your truck take it to a spring shop and have them build a set of springs. They will design them to be longer which will keep the swing arm in its correct position. This will give you the correct spring articulation.
Additionally, If you do lift your truck above the stock height, you will need a different pitman arm on the steering box. If you do not then you will upset the steering geometry and will end up with bump steer. A ff PW will veer left when you hit a bump in the road. This is because as the front springs compress the steering arm will push the drag link into the pitman arm which is immovable in relation to the steering arm. The steering arm being the (easier of the pitman arma and steering arm to move)will actually rotate and cause the truck to turn to the left. Generally, the end of the pitman arm and the end of the steering arm (the connecting points for the drag link) must be at approximately the same height to stop any bump steering. It is complicated to explain in a post but it has to do with the rotation of the drag link that is caused by the steering arm moving vertically with the spring compression and arch that the drag link must move in. As far as I know there are no longer pitman arms available for the ff PW. So you are kind of stuck at stock height with out having a custom pitman. The previous owner of my truck put in a specailly bent drag link to solve the bump steer. It did not do any good as the pivot points were not changed. This is where I learned about bump steering as my carryall had a bad case of it.
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