Advice on leaf springs and un-fused electrical circuits

May 1, 2012 | By Richard Prince


Occasionally I take apart leaf springs to clean them, and in some cases add some additional leaves. I sometimes contemplate painting or greasing the leaves but usually decide instead to coat them with wax. What is the proper way to assemble this type of spring?

Also, I am completely rewiring a 1954 Ford and I’m switching to a 12-volt negative ground. As a guide, I am planning to follow the wiring diagram for a 1956 Ford car. As I think about some circuits being fused and others not I sure like the idea of having a quick disconnect at the battery. Any advice you can share will be appreciated.


John, I recognize your name and location because you’ve written in to Mechanic On Duty several times over the years so I feel like we’re old friends! As to your first question about restoring leaf springs, I always take the spring apart and strip and paint (or powder coat) each individual leaf. If I’m working on a car or truck that’s factory original I’ll paint the leaves to match the factory appearance and if I’m working on a custom car I’ll use whatever finish I’m in the mood for or the customer wants. Coating each leaf with paint or powder coating helps prevent corrosion.

Sometimes leaf springs have liners between each leaf and sometimes they don’t but either way I always lubricate the contact surfaces between each leaf with either anti-seize or wheel bearing grease. As a leaf spring moves through its range of motion the individual leaves actually slide slightly relative to the adjacent leaves and lubricant helps make the movement smooth and essentially unnoticeable. It’s important, however, not to use too much grease because if it oozes out from between the leaves it makes a mess and becomes a magnet for dirt.

As you may have noticed, the center bolt holding the leaf spring together is typically not a regular bolt and you should not use a regular bolt. Leaf spring bolts usually have a specific size and shape and are made from special steel and treated in ways that add considerably to their strength.

If you need to replace the spring bolt you should always use a spring bolt and not a regular, off-the-shelf bolt.

When I first got involved in vintage car restoration I was quite surprised to learn that just about all early vehicles were manufactured with un-fused electrical circuits, and well into the 1950s and even the ’60s many cars were still being built with unprotected circuits. If you’re determined to maintain your vehicle in exact factory configuration, including un-fused circuits, I usually recommend installing fuses or fusible links in hidden places. If you’re not overly concerned with maintaining the original appearance of the wiring system then it’s prudent to utilize fuses throughout the system to protect every circuit in the car.

As far as a quick disconnect for the battery is concerned, that is an excellent addition to any collectible car regardless of whether or not it has un-fused circuits. Though electrical fires in well-maintained vehicles are quite rare they do occur and disconnecting the battery whenever the car or truck is not being used goes a long way in protecting against the possibility of fire. After all, you can’t have an electrical fire if you don’t have electricity.