Originally Posted by matt h
or someone has pumped too much grease in and the inner seal has popped out which is VERY common!!
Agree with what Matt said. Pretty common, if you have grease nipples, to try and get too much in which pushes it through the grease seal out the back.
You shouldn't *need* to put grease in every 500 mi. In theory, it should be a lossless system. Grease will liquefy on running, and re-congeal on sitting.
In practice, you may need to add a bit here and there, but without something like a bearing saver to give you a rough indication, you have no idea how much to add (many have a spring loaded plate that moves as you add grease).
If you do have some sort of indicating bearing saver, my advice is to pump grease in until it is near, but not quite at, full capacity. Lessens the chance of rear seal blowout.
I've attached images of 2 types: One with a blue indicator ring, and one with a sliding plate. For the ring type fill until you can just rock the ring a bit; for the other, fill until the plate is just shy of fully compressing the spring. I'm sure there are other types out there as well.