spring rate
Elder User
Joined: Jun 2003
Posts: 886
Likes: 1
From: Houston/Hope BC
Leaf springs do not have a nice formula like coils do, as I guess you have noticed. 
However, the rate can be computed experimentally. You will need a dial-indicator and some incremental loads. (a forklift and sand bags would sure be handy here, or a bunch of friends with known weights to get into the truck, don't forget to add in the weight of the beers in there hands!)
You need to set up a dial indicator between the axle and the bed to measure the deflection. Put some jack stands or blocks under the front bumper so that no load can be absorbed by the front springs. Start adding weight, directly over the axle and keep it centered to prevent errors. Record deflection and weight and start graphing or charting. Do the math. (Of course, the rate per spring is 1/2 of the measured rate.) I have used this technique to compute and adjust front coils and results were extremely coincident with prediction. I am kinda curious what you find. Is the rate linear or progressive?
As far as changing the rate, the only way I know is to have a spring shop re-make leave(s) thicker or add more leaves in. (Or shorter, but I don't think you want to go there.) GL
However, the rate can be computed experimentally. You will need a dial-indicator and some incremental loads. (a forklift and sand bags would sure be handy here, or a bunch of friends with known weights to get into the truck, don't forget to add in the weight of the beers in there hands!)
You need to set up a dial indicator between the axle and the bed to measure the deflection. Put some jack stands or blocks under the front bumper so that no load can be absorbed by the front springs. Start adding weight, directly over the axle and keep it centered to prevent errors. Record deflection and weight and start graphing or charting. Do the math. (Of course, the rate per spring is 1/2 of the measured rate.) I have used this technique to compute and adjust front coils and results were extremely coincident with prediction. I am kinda curious what you find. Is the rate linear or progressive?
As far as changing the rate, the only way I know is to have a spring shop re-make leave(s) thicker or add more leaves in. (Or shorter, but I don't think you want to go there.) GL
sounds good to me. 
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