How to Fix Leaking Wheel Hub on Your Trailer

If you need to fix a leaking wheel hub on your trailer, I hope the job is as simple as ours was. One of our first rules to follow for any RVer is to investigate all leaks, immediately! We wrote that post our first year on the road. That time is was only a leaky water line. It is even more important to investigate a leaking wheel hub. Whether on your trailer or truck, a leaking wheel hub can be life threatening. That’s why it was scary to discover the leaking wheel hub on our trailer.

leaking wheel hub
Brake dust or grease from leaking wheel hub?

First, I noticed what I thought was brake dust on one of our trailer wheels. Then I discovered it was only happening on one wheel. Then it got worse. With a simple swipe of my finger I quickly determined this was grease. At least that’s what I hoped. I certainly didn’t want it to be brake fluid from our hydraulic trailer brakes.

leaking wheel hub
Rear view of grease from leaking wheel hub.

I had a feeling I knew what was happening. At least I hoped I knew! As a big fan of Ockham’s razor, I knew getting unnecessary information out of the way was the fastest way to the truth or to the best explanation. The best explanation for our leaking wheel hub would be the one with the easiest solution. Thank Dog it was!

…it’s the scientific principle that, all things being equal, the simplest answer is usually the right one.

Jodie Foster, As Dr. Arroway

Most Common Cause for Leaking Wheel Hub

The first step to determine if my simplest explanation for our leaking wheel hub was correct, was to remove the trailer wheel. this is always a scary step. Not because you have to remove the wheel, that’s simple. the scary part is opening that can of worms. What if the simplest solution is not what’s causing your leaking wheel hub? There’s only one way to find out.

leaking wheel hub
Remove wheel to determine cause of leaking wheel hub.

The most common cause for a leaking wheel hub is a loosened hub cap. I do not mean the decorative cap in the center of your wheel. Yes, that’s technically a hub cap. But it does not leak. While the visible cap does cover your hub assembly, it is Primarily decorative. Sure, it keeps dust rocks and road grime our of your wheels. Bit it does not function as any sort of seal.

Step 1: Remove the trailer wheel to expose hub cap and seal.

leaking wheel hub
Leaking Wheel Hub Seal

Phew! Ockham was right once again. Notice the gap under the hub cap sealing axle grease inside our wheel hub. The hub sealing cap on this wheel had come loose. That was allowing grease to get out. Centrifugal force of the spinning wheels was forcing grease out through the small gap. thankfully, I investigated the issue quickly. We had lost very little grease.

leaking wheel hub
Repair leaking wheel hub to prevent loss of axle grease.

Left unattended, the cap could have come off altogether. Ignored, a major grease loss can occur. That would be hard to overlook. But the damage could be very severe. Friction from the loss of grease could cause an expensive repair, or much worse.

Simple Fix: Inspect wheel hub seal and replace cap.

wheel hub inspection
Inspect leaking wheel hub for damage.

Simple Steps to Repair Leaking Wheel Hub

Remove the inner rubber seal to expose your axle hub. Check for any sign of wear or looseness on the castellated bearing nut. Ours was in good shape, as ample grease was present around the nut crown. the hub should not be filled with grease. This may indicate a broken seal. If your hub has a zerk fitting (aka: grease nipple, grease fitting), and you have a grease gun, you may want to top off. But just how much grease should you add?

Our hubs do have zerk fittings. But I don’t have a good compact grease gun. Maybe Santa will bring me one for Christmas. Hint, hint, Rene. Then, as usual, my gift will entail another RV maintenance project of some sort.

TIP: Over-greasing the hub pushes grease out the hub seals. Accumulated grease attracts dust and dirt. As a result, contaminated grease can damage moving parts. Too much grease also causes churning and higher temperatures.

tight hub seal
Ensure good seal around hub cap to prevent leaks.

Replace the rubber seal and use a rubber mallet to firmly seat the hub cap around the wheel hub. (Clean all components before replacing the wheel. Make sure you do not have any grease on the brake disc or pads.) You will notice from my photos, that someone at some point used a hammer. You want to use a rubber mallet to re-seat the cap. Using a hammer can dent the cap. This may have been the reason ours came loose, causing the leaking wheel hub.

clean trailer wheel
No more leaking wheel hub!

But Wait, There’s More!

Once you’ve re-seated the inner hub cap and cleaned everything up, you’re almost done. Replace the wheel and hand tighten all the lug nuts. Then lower the trailer axle off your jack stand. You did use jack stands, right!? 😉

torque trailer wheels
Re-torque your wheels whenever you remove them!

One More Step: It is good practice to torque your wheels every time you put them back on. In fact, check the torque on all wheels while your at it. Use the torque specification for your wheels. I keep ours at 100 lbf⋅ft.

There’s not much I enjoy more than a simple fix!

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