Spindles are the innermost part of the trailer wheel and axle assembly. They provide a surface for the wheel bearings and wheel hub to rotate around.

David Oliver/Getty Images

If you want to keep your trailer in road-ready condition, then you should expect that there'll also be a good deal of trailer maintenance that you'll need to complete. Tires and brakes, lights and trailer wiring, suspension components and hardware -- all of these (and more) need attention for your trailer to remain in proper operating condition. In fact, you may find yourself in front of the local trailer supply parts counter more often than you wish.

If you hang around the parts counter long enough, chances are that you'd eventually hear someone say that they need one or more spindles for their trailer. If you've never heard of a spindle before, your reaction may be to furrow your brow, mumble its name again under your breath or maybe even expel an audible "huh?"

Spindles, like most trailer parts, rarely receive much attention -- until they need to be replaced. But what are spindles? What are they used for, anyway? What purpose do they serve? On a trailer, the spindles are located at the very ends of the axles and they definitely do serve a purpose. When you're towing, spindles are the part of the trailer axle assembly that the wheel hubs (and wheels) rotate around. Trailer spindles provide a surface for the inner and outer wheel bearings to roll on -- or rather, to roll around. The inner and outer wheel bearings keep the wheel hub and the spindle from actually contacting one another. In other words, the spindles are literally at the center of it all.

Now that you have a general understanding of what spindles are and the purpose they serve, what about replacing them on your own trailer? Should you pick up a new set of spindles along with your other towing supplies? Is it a good idea to tackle this project on your own, or should you leave it up to the professionals? You may want to read the next page before you decide.

­