Hub grease seal.

ScottG wrote:
My experience on several trailers over 30+ years has been that they leak past the seals about 40~50% of the time. That's even when we spun the wheel and followed the directions religously.
Even if they do happen to work, you have to fill the hub completely before it comes out the front. That means the old used grease in the rear bearings has to be pushed out where it then travels through the hub and into the outer bearing. At that point you have a lot of "used" grease mixing with "new" grease to lube your bearings.
So even when it works, it's a mixed bag.
You're also going to go through about 1/2 tube of grease the first time becasue it takes that much to fill the hub - which they teach you in mechanics school is a bad idea because it causes the hub to run hotter.

Frankly, none of this is needed. Like the wheel bearing they use on many vehicles, they only need to be repacked every 40K miles or more. (They certainly dont need more grease shoved in them periodically). I put that many miles on my last trailer before repacking. When I got in there, I found it was totally unnecessary. Yes, the grease was discolored - it doesn matter. It was still perfectly serviceable.
I would check them one a year for play or roughenss and then let them go another year.

Not willing to trade insults or argue over it. Those are my real life experiences.

I pretty much agree with the above, even though my reasons are different.

I believe many of the seals leak because they are damaged during assembly. After looking closely at the bearing and seal surfaces the last time I had my wheels off checking the brakes, there were nicks abounding near the bearing and seal areas. Personally I was amazed that I had no grease leaks. I don't believe it is a problem inherent to the EZ Lube system, but the fact that the EZ Lube system allows you to add grease that will make it past those damaged grease seals.

And I agree 100% with the frequency of wheel bearing repacking.