So what exactly is a spindle?
Before you can determine which spindle you need, you need to understand what
exactly a spindle is and why it is so important. In short, you will find a
spindle at the very center of a trailer wheel. It is what the wheel hub and
bearings rotate around. Without a spindle you would not be able to have a
Unfortunately, most people do not even think about their spindles until they
need to be replaced. However, this important part to your trailer should never
be forgotten. Whether you are hauling boats, cars, or jet-skis, spindles are a
vital piece to proper operation. They can be found on each end of the axles. As
you begin to move your trailer, the wheels start to turn. How are they able to
turn? Because of the spindles, of course! The small, narrow, circular objects
provide the surface needed for the rolling movement to occur. Keep in mind that
the wheel hub and spindle never actually touch thanks to the inner and outer
wheel bearings. The entire wheel revolves around the spindle, making it the
literal center of it all.
Okay, I understand what a spindle is, but how do I find the right
replacement one for my trailer?
The good news is that all bearing manufacturers use the same numbering scheme.
These common numbers can be easily found stamped on each bearing. Since these
numbers are universal, it is very easy for us to determine what spindle you need
based solely on the type of bearings that you have.
So where can you find the bearings? First, you will usually find both a front
and rear bearing in a hub. The front can be identified because it is the one
closest to the street, and the rear bearing is consequently closest to the
trailer. It gets a little complicated because not all bearing pairs are the same
size. This is because some spindles are tapered while others are straight. The
tapered spindles require a bigger rear bearing than the front one. However,
should your spindle be a straight spindle, the front and rear bearing sizes will
Once you have identified and recorded the bearing sizes, you can simply use
the following chart to determine which spindle you need to make your trailer
Bearing Part Number
Spindle Diameter (in)
||1 1/16 in
||1 3/8 in