The next time you have the opportunity to see an uninstalled leaf spring, be sure to notice the bolt that is holding all the leaves together.
That bolt is known as a centerbolt. While on most springs, it’s not in the center of the spring lengthwise ,it will be centered width wise.
Leaf Spring Centerbolts will serve a few very important functions. First and foremost, a center bolt holds all the leaves together. And another very important thing that little center bolt does is locate the spring to the axle. Just think about it. Without the centerbolt head fitting into the hole in the axle spring seat, the axle would just slide back and forth over the spring.
And there is one more thing that centerbolt does for us: it tells us how the spring mounts to the axle. If the head of the centerbolt is on the bottom of the spring, the axle is under the spring.
If the head of the centerbolt is on top of the spring, the axle is over the spring.
And the final thing, the hole in each leaf that that centerbolt goes through is the starting point for all length measurements of each leaf.
Now, with all this new knowledge, you will never, ever look at a centerbolt again without respecting its importance.