Iam building a 39 ford truck and Iam not sure what coil over spring weight I should use. What have you used and how well did it ride for you? Thanks merle
Depends where/how they are mounted. Too many variables. Getting it right on the first try is very unlikely unless you've built a similar setup before. I'd start with 300lbs/in and go from there. Summit has QA1's for pretty cheap. Also, bottoming out a shock is often terminal to the shock, so check your max travel carefully.
My suggestion is that you dump the coil over idea if you are building a conventional pickup truck with a box and intend to throw cooler, chairs or misc junk in the back. My way of thinking would be installation of a parallel spring kit rather than coil overs. This would provide a longer spring base and a potential a better ride package.
you wont know for sure until its all put together for the weight of the rear. I ended up with 3 pairs of springs before I got it where I wanted, ended up with some 175# that are mounted strait up and down. Your shock angle will also affect the spring rate, if you have an idea of the approximate weight it will give you a place to start
In answering your original question and not whether you should run them or not. On the rear I would say 200 lbs, but not more than 250 maximum if you are gonna load the bed. I run 275lbs on the back of my 27 sedan delivery and they are fine and most of the shocks are adjustable for ride height.
As stated above, I think 175 to 200 lb springs would be about right. Most rear coilovers use a 12in spring and install at a height of 14 to 14.5 in. center to center. We never angle the top inward more than 30 degrees. We determine the correct spring rate when the shock is at ride height with about 1in. of threads showing on the bottom. This seems to work well for us. SPEEDY
175 should get you close. Be sure to get the right length spring to allow 1-2" of spring compression with the shock close to the middle of its travel.