How Trailer Spindles Work


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.
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.

­

Installing Trailer Spindles

Spindles are welded to the axle, so a do-it-yourself replacement may be out of the question for some trailer owners.
Spindles are welded to the axle, so a do-it-yourself replacement may be out of the question for some trailer owners.
Gene Krebs/iStockphoto

As you can imagine, lubrication around the spindle is critical to keep the bearings spinning and to prevent the hub from making contact with the spindle's surface. Grease caps normally do a fine job of keeping grease in place in typical towing conditions. However, on a trailer that's towed through sand or a regularly submerged boat trailer, for example, the grease -- even with properly installed grease caps -- can become contaminated or even washed away completely. That's why you must frequently inspect your spindles for signs of wear.

There are several reasons that you may need to install new spindles on your trailer. For instance, you might have to replace the spindles if your wheel bearings failed, or if your trailer was involved in an accident where the spindles were bent or cracked. Another situation where you may find yourself pondering new spindles is if you decided to build your own trailer axle or even your own complete trailer. After all, you simply can't pull a trailer down the road without spindles -- not very far, anyway.

There are very few bolt-on spindles available; in fact, most spindles are welded to the axle tube. Replacing a spindle requires breaking the existing weld and then welding the new spindle in place. Since welding axle components together probably falls outside of the comfort range of a lot of weekend mechanics, the installation of spindles in the typical homeowner's garage or driveway isn't very likely -- but it is possible.

By no means are we trying to discourage you from attempting a do-it-yourself installation of trailer axle spindles, but unless you're a skilled welder, this may be one of those jobs that are better left to the professionals. It's critical that spindles are properly aligned and secured to the axle. A licensed trailer repair facility should easily be able to install a new spindle or two. Remember, sometimes it may be worth the extra cost to save the time and frustration that can sometimes accompany a difficult (and unfamiliar) repair.

To read more about towing, spindles and other related topics, follow the links on the next page.

Related HowStuffWorks Articles

More Great Links

More Great Links

Sources:

  • Champion Trailer Parts Supply. "Spindles and Parts." (Oct. 26, 2008) http://www.championtrailers.com/spindles_n_parts.html
  • etrailer.com. "Spindles." (Oct. 27, 2008) http://www.etrailer.com/c-s.htm
  • Motor Era: Automobile History. "Dictionary of Automotive Terms: Sp." (Oct. 27, 2008) http://www.motorera.com/dictionary/SP.HTM

­