No matter how much planning is done project vehicles seem to establish their own direction. Take our Hot Rod Hauler as an example, we had accomplished many of the original goals—lowering the truck on both ends was one of them-- and now we’re going to redo the rear.

In stock form, the truck was roughly three inches lower in front than in the rear, but that rake never really bothered us. We installed dropped axles from Tech that dropped the front 3 inches and modified the stock rear springs by removing leafs and got the back down roughly the same amount. Unfortunately, when we thought we were done with the suspension, we stood back and took a look at the F-350 and didn’t like what we saw. It still had the nose down stance but for some reason we liked it less than when it was stock and sat at the same angle, and their were other problems as well.

One of the first things we noticed with our modified stock springs was wheel hop on hard acceleration and braking, that was something new and unwanted. In addition, adding the tongue weight of our loaded car trailer caused the springs to flex at an odd angle (no doubt from a lack of support due to the removal of leafs) even with the auxiliary airbags. Now we were concerned about breaking a spring with a load, so we did what we should have done in the first place, we called Mike Eaton. Mike is the man in charge at Eaton Detroit Spring, a company that has been in business since 1937. They have over 24,000 blueprints for OEM springs, and can come up with 166,000 spring combinations. If your needs still aren’t covered there’s an in-house design staff that can create a custom leaf or coil.

Springs Simplified

It’s said that if something looks simple look again because you’re missing something. That’s certainly true of springs, they’re more complicated than they look, but we’ll rely on excerpts from Mike’s “Spring 101” to explain it all.

By design, leaf and coil springs support the weight of the vehicle, provide cushioning with adequate stability and resistance to side sway and rollover, and resist cornering effects when negotiating a curve. In addition, leaf springs connect the axle to the vehicle, transfer driving and braking forces between frame and axle while resisting “wrap up.”

Quality springs are made from high alloy spring steel known as SAE-5160. Good springs have a memory that allows them to return to the original position time after time. And while it is true that over time springs will settle and lose their ability to support weight, springs made from SAE-5160 will outlast the others many, many, times over offsetting any cost savings.

Spring Rate vs. Load Rate

While these two terms sound similar they are not the same. Spring rate can be simply stated as the amount of weight required to deflect a spring (any spring) one inch. The lower the rate, the softer the spring. The softer the spring the smoother the ride.