JRscooby wrote:
I have no experience with axles that have the zerk. I can see how it would be easy to push grease past a seal, or even push a seal out. After all, a hand grease gun pushing grease is used to tighten the tracks on a loader.
But I have worked on lots of things. Many seals fail because of bad installation. That kind of thing happens shortly after put in service. If it has worked for a while, from a rock crusher to trailer to little bearings on antique motors, if a seal where a shaft spins, or something spins on a shaft, there is a bad bearing. Now did the bad bearing let things wobble ruin the bearing? Or did the escaped lube let the bearing get too dry? No matter, they fail together.
Now when you add the zerk, and grease pumped in the bearings could still be good.
You alluded to using a grease gun to "tighten tracks" as an application of a grease gun.
Most folks do not really understand just how much pressure can be developed by a hand pumped grease gun nor the amount of grease per pump which can vary, a lot.
Per
HERE is some examples..
"A basic step that is often overlooked is training the lubrication technician on the proper use of the grease gun. A high-pressure grease gun delivers pressure up to 15,000 psi. Most bearing seals will rarely handle more than 500 psi. A grease gun in the hands of an untrained technician can compromise the bearing’s seal and lead to early failure. The compromised seal invites dirt or other foreign materials as well as overlubrication due to little or no back pressure."Now, I have seen mentions of hand pump grease guns at a min of 1,700 PSI and typically 2,000 PSI which means that even the lowest pressure guns WILL breach a standard single lip seal with very little pumping..
The EZ lube system is supposed to use a double lip seal because of this issue.. I highly doubt that a double lip seal is going to be able to withstand 2,000 psi or more for very long..
Not to mention folks failing to read the manuals which tell you to TURN the drum while pumping and mechanics which just assume plugging a grease gun without TURNING the drums is fine.. The end result is a blown seal letting the grease expand out into the brake shoes..
I personally have no use for this gimmick (and one of my trailers does have it), PA DMV rules requires a State inspection on trailers with brakes.. That inspection means at least TWO drums (one on each side)MUST be pulled every year and the brakes inspected.
Obviously if you are just pumping a couple of squirts a year into the bearings you are never going to actually LOOK at the brake shoes or drum conditions, are you?
Then add in that grease guns vary in how much grease they pump, some can pump a lot and some not much. So when the axle manufacturer states one or two pumps is good.. You might never fill the empty cavity as shipped new for years which results in dry bearings.. Or with high volume pumps waste more grease than you would if you physically repacked them and risking damaged seals/leaking grease..
I personally like to pull the drums myself if not yearly at least once every two years..
This gives me the chance to check the brakes myself, clean and check the bearings for wear problems and repack the bearings with new grease.
It isn't that I don't trust mechanics, I would rather find and correct a problem BEFORE dragging the trailer to the inspection station. This avoids having a rejected inspection and dragging it home then fixing then dragging it back for the inspection, saves me time and saves the inspection mechanic time.
Grease and a new seal are cheap, replacing a damaged drum, brake backing plate, bearings or axle while on the road is not cheap and not to mention will totally ruin your trip.
