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National Springs Custom Leaf Springs - Leaf-Spring Rethink

Posted in How To on July 25, 2008
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Photographers: Fred Williams

Though it's one of the oldest suspension technologies there is, leaf springs are still very relevant in modern-day suspensions. And it's all too often we hear enthusiasts talk about how they have to get rid of their leaf springs because they ride too stiffly, or they don't have enough travel. And lots of times, those same individuals are automatically thinking the next step has to be to a four-link and coilovers. But this isn't the case! In fact, you might not even need a new set of leaves, much less a new suspension setup.

Chances are your existing leaf springs can be modified to work better with your vehicle application. You see, leaf-spring manufacturers make leaf springs for a semi-universal fit to particular models of vehicles. They try to account for the way most customers are going to use their trucks, the height of lift a customer wants, the size of the shackle, if the customer is hauling heavy loads, etc. On top of that, they have to do it at a cost point that is reasonable enough for them to still make a profit. Therefore, the chances are that even if your leaf springs are almost perfect for your truck, you can probably improve them with some custom tuning for your particular truck.

We've had a couple sets of custom springs made by National Spring in the past, and we've had some really good luck, but we've changed the builds of our trucks a little bit over the years and therefore have changed the loads and forces on the suspensions. We called up National Spring to get some advice and found that we could modify our existing springs to work better with our current builds. Travel could be increased, spring rate and load-carrying capacity could be increased or decreased, and the leaves could even be straightened if some of them were damaged or had an "S" shape to them from wrapping up.

We were able to get our springs back onto our truck and make a run to a nearby off-road area. Bill had done a great job getting our National springs to work better on our truck, and because he was able to keep every leaf in the pack, we didn't feel like it had any more spring wrap than it did before we had them modified. The rear would stay on the ground and wouldn't lose traction as easily as it did before when the rear was stiffer. And now, we don't have to worry about bending our leaf springs because our shackles were too short.

If you haven't had it done yourself, then you might have a friend who has had his leaf springs re-arched before. And you've probably asked yourself, "Isn't that temporary? And won't they just settle back to their original height?" Well, yes and no.

The metal in the spring leaves has a certain grain structure, and the metal definitely has memory that brings it back into a certain shape. The temporary or permanent status depends on the age of the spring, how many leaves are in the leaf pack, the thickness of the leaves, and what the original arch was. If you've got semi-new 10-leaf springs, and you want to gain 2 inches of height, then it can probably be done permanently. If you've got some old factory four-leaf packs that you want to crank up 4 inches, then they'll probably be flat again by the time you arrive home.

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National Spring Inc.

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