Forum Discussion
Racer-X-
Apr 28, 2019Explorer
I guess I'm late on this discussion. I just joined the forums here for other issues.
For future readers who might find this thread in a search or want more information, I thought I'd share some details.
Short answer, if OE springs are still available, like from GM or Ford or whoever, use your VIN to look up what was installed, and use a replacement for the original. That's the easiest solution. If you want to "do something different," then you should understand a bit more about how springs work and how y our suspension works.
Springs have two ratings that are important. One is the load capacity of the spring. This is how much weight can be put on the spring without damaging the spring (permanently deforming it or breaking it). For safety reasons, you need a spring that exceeds 1/2 of the GAWR for the axle that it's installed on. The reason for this is fairly obvious.
The other rating for the spring is the spring rate, expressed in "pounds per inch." This is how many pounds of weight must be applied to the spring to compress it one inch. The stiffer the spring, the higher this rate will be. Also note that for most suspension designs, the "wheel rate" in pounds per inch is different, often lower than the spring rate of the spring itself. This is because the suspension usually has leverage on the spring. For a dual wishbone type suspension, the wheel rate is the spring rate times the ratio of the distance from the spring center to the control arm pivot point to the distance from the lower ball joint to the control arm pivot point.
For a simpler explanation, if the center of the spring is half way between the control arm pivot (the bushings) and the lower ball joint, then the wheel rate will be half of the spring rate. That's because the wheel has 2:1 leverage on the spring.
For future readers who might find this thread in a search or want more information, I thought I'd share some details.
Short answer, if OE springs are still available, like from GM or Ford or whoever, use your VIN to look up what was installed, and use a replacement for the original. That's the easiest solution. If you want to "do something different," then you should understand a bit more about how springs work and how y our suspension works.
Springs have two ratings that are important. One is the load capacity of the spring. This is how much weight can be put on the spring without damaging the spring (permanently deforming it or breaking it). For safety reasons, you need a spring that exceeds 1/2 of the GAWR for the axle that it's installed on. The reason for this is fairly obvious.
The other rating for the spring is the spring rate, expressed in "pounds per inch." This is how many pounds of weight must be applied to the spring to compress it one inch. The stiffer the spring, the higher this rate will be. Also note that for most suspension designs, the "wheel rate" in pounds per inch is different, often lower than the spring rate of the spring itself. This is because the suspension usually has leverage on the spring. For a dual wishbone type suspension, the wheel rate is the spring rate times the ratio of the distance from the spring center to the control arm pivot point to the distance from the lower ball joint to the control arm pivot point.
For a simpler explanation, if the center of the spring is half way between the control arm pivot (the bushings) and the lower ball joint, then the wheel rate will be half of the spring rate. That's because the wheel has 2:1 leverage on the spring.
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