Dear Dave,
You are absolutely the best and most detailed, knowledgeable individual that I have ever seen or heard or read! Thanks for being so thorough all the time with your responses to someone’s inquiry. My question is simple. When you grease the Zerk fitting on travel trailer axles, does the grease get to the inner bearing as well as the outer bearing? Once again, thanks! Thanks for being such a detail-oriented, hard-working individual. —Manny, 2014 Keystone Outback 323BH
Dear Manny,
First, thanks for the kind words. (Your check is in the mail.)
There are several types of axles and bearing assemblies, so it depends on what type is on your trailer. The older, traditional bearing and axle assembly did not have an exterior grease zerk. You had to take the entire assembly apart to clean and lubricate the inner and outer bearing.
Bearing Buddy
The first time I saw an actual exterior grease zerk was a product called Bearing Buddy. Many are using on their trailers thinking it will easily grease the bearings without the need to disassemble everything.
This is a mistake, as the Bearing Buddy was designed for boat trailers and is an aftermarket product. It is only intended to fill the Bearing Buddy with grease to reduce moisture from penetrating into the axle’s bearing assembly when submerging the boat trailer into water during loading and unloading. Loading up a Bearing Buddy fills the cylinder, which does apply grease to the surface of the outer bearing. But it does not apply grease to the actual bearing and not to the inner bearing.
The misconception, in my opinion, is they are advertised for RV applications but most people do not read the intended purpose. According to the website, the Bearing Buddy has an internal spring that applies pressure (3 psi) to the seal so air and ultimately moisture cannot be sucked into the hub when it cools from the heat of road travel. From my experience, the only thing these lubricate is the rims and side of the trailer!
Next generation of external grease zerks
The next generation of external grease zerks actually are integrated into the axle spindle. They do allow grease to go through a hole down the center of the spindle to the back and push old grease out past the inner bearing and outer bearing. Dexter has the E-Z Lube version, which might be what your 2014 model has. Lippert has one, as well, but I doubt they were offering this until recent models.
Here is a diagram from Dexter showing the grease flow to the back and how it pushes the old grease through the inner and outer bearing. If you have this system, you will see the old grease coming out of the outer bearing.
Bearing maintenance
Even with the E-Z Lube and other quick zerk lubricating systems, they are only a band-aid to proper bearing maintenance. You still need to disassemble and repack bearings at least once a year or every 12,000 miles. Just applying new grease does not show how the bearings are wearing or burning.
Both Lippert and Dexter recommend repacking and inspecting annually. This provides the opportunity to clean and inspect to make sure all bearings are spinning freely. It is also important to replace the seals and inspect the rotor and brakes.
Do not use a hydraulic or powered grease gun as the excess pressure could cause damage to the seals. An old-fashioned hand pump grease gun is still the best.
I also recommend checking the temperature while traveling just to make sure nothing is overheating. A laser temperature sensor like this one on Amazon is great to get a reading of the hub in the center for bearing temperature, the rotor for brakes, and the tire.
It is not uncommon for the temperature to be higher than ambient temperatures. However, when it spikes 40+ degrees, you know something is not right. It is much cheaper, and easier, to repack wheel bearings in a service bay than on the side of a road!
You might also enjoy this from Dave
How often should I repack my RV’s wheel bearings?
Dear Dave,
I have read so many different opinions about whether to repack wheel bearings or use the external grease nipples. Some things I have read: that wheel bearings should be repacked every 12 months, just inspected every 12 months, external grease application is sufficient, and if you add too much grease through the external nipples you could blow out the seals. What is your recommendation on wheel bearing maintenance? Thank you. —Leigh, 2022 Grand Design Imagine 22MLE
Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”
Read more from Dave here.
HAVE A QUESTION FOR DAVE?
Send your inquiries to him using the form below.
##RVDT2278
If you have a new trailer, I would suggest you have those bearings & brakes inspected in much less than 12,000 miles. While not experiencing any problems, I took my 2022 trailer into a local shop at roughly 6,000 miles. The service tech said in polite terms that he thought I was wasting my money.
Picking up the trailer a few hours later the tune changed to ‘boy are you lucky you came in’. Barely any grease from the factory, damaged rear seal on one wheel, and brake adjustment was manual, not automatic as the tech expected.
Now that I KNOW the axles are properly lubed, I can use the expected maintenance cycle.
Personally I do not recommend these so called bearing buddies on anything but a boat trailer as a lot of so called “axle mechanics” have a tendency to over grease them pushing grease through the seal onto the brake shoes.I know of a particular manufacturer of RV’s that uses cheap Chinese grease seals that will not take the pressure a grease gun puts out and will fail to keep grease from saturating brakes. Try stopping a large trailer with greasy brakes.You will have a visions. It is better to hand pack wheel bearings.
If you grease thru the e-z lube system, rotate the wheel as you apply grease.
I’ve never understood 12,000 mile or 1 year. What’s the difference between my truck front wheel bearings and a trailer? 187k on the truck and never been touched. Over 200k on truck before it.
If your truck is less than 25 years old the front wheel bearings are a sealed bearing and can not be repacked. Your trailer bearings are not sealed and are the same design as wheel bearings 100 years ago
Thank you, Dave! 🙂 Merry Christmas!
“You still need to disassemble and repack bearings at least once a year or every 12,000 miles.”
I don’t personally know a single RV owner that does this. Having never done such a thing I wouldn’t attempt it, no doubt the dealers are expensive. My local auto place can do it although my 5th wheel takes up a lot of their space out back. They did it once when the brakes needed some work, I didn’t write down the individual costs that time.
I split the difference. For more than 10 years, I use the zerk fitting to grease my bearings every other year, rotating the wheel and gently pumping in the new grease. On alternate years I do a full hands on greasing and inspection. The last time I did the hands on, year No. 11, I found some very minor pitting on a couple of bearings on the inner bearing of the left side. Races and spindles were good. I replaced all the bearings and seals this last go around. I’m 80 and in good health and find the job not too hard to do.