Wheel Bearing Maintenance

One of our NIU members experienced a wheel bearing failure, shortly after being serviced by the local Airstream dealer. Here are a few tips for people who maintain their own bearings, or make sure the RV mechanic is doing it right..

Our trailers use two tapered roller bearings per wheel.

Outer bearing – Timken P/N LM 67048,  or  Outer bearing – Timken #473336 , Outer Bearing Race -xxxx
Inner Bearing – Timken # 25580     Inner Bearing Race: 25520

Grease seal – National oil Seals P/N 412920 (2.258 ID x 3.371 OD x .375 thick )
Hub Seal – TBN # TCM 22333 or Seal – TBN # TCM 2132TB

Kodiak Disc brakes Hub Parts:
Inner bearing: Timken 25580    Inner Race -Inner race: 25520
Outer bearing: Timken 15123   Outer race –  Timken 1524
Seal:  RG06-070  (Inner diameter: 2.250″ Outer diameter: 3.376″)  Double lip seal with spring

Typical causes of bearing failure:

Fatigue failure (spalling)- is when a fatigue fracture originates below the surface of the races or roller and the surface metal comes loose forming a very rough spotty surface. Upon dis-assembly, the grease may still look OK (if the wheel was not run too long after failure). If it has been run for many miles, the bearing will overheat and the grease will run out. Even if only a few spall marks are present, the bearing and the raceways should be replaced. Spalling at the small end of the bearing indicates it was adjusted too tight. Spalling at the large end indicates they were adjusted too loose.

Over Heating – This may be caused by the bearings being: adjusted too tight, improperly greased, mixed or improper type of grease, too much weight, or the brakes dragging overheating, causing the grease to melt and run out.  Discolored bearing surfaces (blue or brown) indicate an overheated bearing.  When disassembled, the bearing would, at first, appear to have been under lubricated, but that may not be the root cause of the problem,

Contamination – Bearings may become contaminated by water or dirt, or been repacked with an incompatible grease. Bearing races may have scratches and a mildly rough surface.

Routine Observations
Check the axle caps for bearing heat while you are filling the gas tank.  A hot bearing should be serviced very soon. The suspect wheel should be raised off the ground (boards under tandem wheel) and rotated by hand to detect any roughness.  Check for the proper amount of looseness (0.005 – 0.020 in.) or play in the wheel,(as measured at the wheel rim edge) by twisted from right to left or up and down. Brake drag should be minimal.  If there is excessive brake drag, this can overheat the wheel bearings.

Preventive Maintenance- Wheel Bearings
Airstream recommends: clean, inspect, and re-lubricated the bearings once a year (usually at the same time the brakes are checked). For long distance travelers, Airstream recommends the bearings be cleaned, inspected and repacked every 20,000 mile. You will need a grease seal puller to examine the inner bearing. There are several types of wheel bearing grease on the market. Not all of them are compatible. If you are switching grease types or do not know what the last grease was, clean all the old grease off before repacking the bearings. Grease is made from an oil and a fatty soap (which provides the viscosity to keep it in place). Older greases use sodium or calcium soaps. Newer greases are lithium, aluminum, or are synthetic based. Lithium greases have higher temperature ratings and are suitable for bearings that run hotter (such as on trailers with disk brakes}.  Airstream recommends a lithium grease meeting NLGI grade 2 rating per ASTM 265 (which should be marked on the grease container). The condition of the grease seal should also be checked and replaced (if necessary) at the time the bearings are repacked. To properly reset the bearing tightness, the retaining nut on the axle should be torqued with a wrench to 12 ft. lb., while rotating the wheel. Then, the nut should be backed off and re tightened by hand until snug and then backed off to allow the cotter pin to be installed in the next available slot in the castle nut. The wheel should then be rocked and a small amount of looseness or play should be felt (0.005 to 0.020 inches when measured at the wheel rim). This is equivalent to the 0.001 to 0.010 in. of end play specified in the Airstream service manuals. Here is a link to a complete manual –

New Design Reese Dual cam hitch  Use a thin jam nut ( 0.72″ thick) when installing the trailer ball.  Use of the standard 1″ thick nut can interfere with the trunions when parking in sites that require tight turns. If you do not have the thin nut, drop your W/D bars before attempting to park.

Before attempting to park, disconnect your frictional sway dampeners. Otherwise you might bend them.

Drop the W/D bars before backing into an uphill parking spot. This will raise the rear of the trailer and help to prevent digging the rear bumper into the ground or pavement.

Tire Maintenance and size – link click here

Changing tires on an Airstream   Do not allow a tire mechanic with a jack and an air wrench, too come close to your Airstream.  Speaking from personal experience, he can do thousands of dollars of damage within a minute.  He can crush your axles or holding tanks with his jack, or overstress or strip your studs and lug nuts with his air wrench.

Loosen the lugs slightly while the bad tire is on the ground. Use boards, under the good wheel (s), and tow vehicle to pull the trailer forward onto the boards. The bad tire will drop a couple inches but will eventually get off the ground. Keep the truck attached, or put in your wheel chocks.  Remove the lug nuts and bad tire.  Install the replacement wheel. (Check for brake drag and smooth wheel bearings while you are at it.) Tighten the lug nuts. Pull forward, off the boards, and re-torque the lug nuts.

Tire stem recalls and cautions. Tire stems can be a weak point for many wheels.  The stems have a core valve, rubber seal to the metal rim, and a vertical extension (that may be rubber or metal).  Leaks may occur in each of these locations.  Tire stems are made in the millions and there is no lot number or control of where they go. Recently, one Chinese manufacturer made about 15 million defective ones, which did not resist ozone very well.  They develop cracks around the seal to the metal rim.  Sometimes, they fail losing air pressure rapidly causing blow outs.  Sometimes, you can detect potential problems by flexing the valve.  Speaking from personal experience, do this only when you have the ability to fix it, as the tire can lose tire pressure rapidly. Metal stemmed valve (used on higher pressure truck tires) do not seem to have as many problems and are recommended for our trailers. We had two stem failures and subsequent tire replacements during our 2015 Arizona trip.

Tire Date coding -Tires made after 2000 have a four-digit DOT code. The first two numbers represent the week in which the tire was made. The second two represent the year. A tire with a DOT code of 1109 was made in the 11th week of 2009. Tires with a three-digit code were made prior to 2000 and are trickier to decode. The first two digits still tell you the week, but the third digit tells you the year in the decade that it was created. The hard part is knowing what decade that was. Some tires made in the 1990s (but not all) have a triangle after the DOT code, denoting that decade. Tires without that without the triangle and a code of “328” could be from the 32nd week of 1988 — or 1978.

Weight Distribution Hitch setup. link: click here

Restoration Manual Link: click here

Dexter Axle and brake maintenance – link: click here

Portable Generators –  There are two types:  Cheap, low capacity emergency, constant speed, units using two cycle motors and give poorly regulated AC alternator 110 outputs.  More expensive, higher capacity, units with 4 cycle engines using DC generators feeding Electronic inverters, resulting in better regulation of voltage and frequency.

Cheap 2 cycle alternator generators do not create well regulated voltage or frequency. Electronic devices, or synchronous AC motors. do not run well with these generators. Two cycle engines can not be effectively muffled, without losing power, and therefore they are louder. They can be used for emergencies or camping without electronics and might save your the food in your home refrigerator during prolonged power outages.

The newer, more expensive,  DC generator units with Inverters usually have an “i” in their model designation. They still have total power capacity limitations.  You need at least 2 KW capacity to run an Airstream air conditioner.  The air conditioner start up current draws can cause problems for some of the lower capacity “i” units.   They use  4 cycle engines, which can use effective exhaust mufflers, therefore are quieter.  NIU member, Rick Wendorf’s Yamaha i  2400 tested with his digital power supply analyzer, showed the output was well regulated and exactly 60 cycles,

If you have a Honda”Two pack” generators, they have a twist lock “marine type” 20 amp 110 volt outlet.  You will  need to carry a male marine twist lock to 30 amp RV female dogbone to connect to your Airstream.  Airstreams with dual air conditioners need 220 volt, 50 amp. connection supply.

You should not operate a generator the same time as you are connected to “shore” “campground” power.  Properly ground your generator by attaching a wire to the stud provided on the generator and connect it to a good ground or hammer a ground rod into the ground.

Dwight Dixon – Revised 12/20/15


“Hot Skins” :  IE :Outer Skin of the Airstream (or RV) has AC voltage present

To have a shock or electrocution occur, you need at least three things to be wrong.
ONE: Poor grounding on the campsite receptacle.  It is not unusual for the ground on some outlets in houses or campgrounds to be poorly maintained and not provide a sufficient ground.  (I usually check a site before I back in. ) I use a simple three light tester you can buy for $3 at a local hardware store.  Use a 30 amp to 15 amp dog bone adapter to use the 3 light tester for 30 amp RV outlets.  This type of tester is good, but not completely foolproof, as demonstrated on some You Tube videos. A high voltage non-contact detector ( Milwaukee (click here), Greenline (click here), Harbor Freight (click here) or other) are more foolproof.  
 TWO: Failure to properly ground the trailer.  WBCCI suggests you have at least one metal jack stand or metal stabilizer in contact with the ground.  (Parkers usually check for this at International rallies.) 
THREE: There is an internal short within a plug-in appliance in the trailer, or a short, or reverse contact in the trailer wiring.
If these three things occur, and you make a good contact with damp grass or ground when you reach for the trailer door, you have a real problem.  It can also occur when you step out of the trailer onto morning dew, while still holding on to the metal handle on your trailer.  A three year old (non-club member) child was electrocuted by his family’s Airstream on 6/30/2015 at Amboy, IL. (They were not club members.)

 NEVER accept a feeling of any shock from an RV or appliance. A small  shock is a warning that, the next time somebody touches your RV they could die from electrocution.

NIAC has purchased a Milwaukee non-contact voltage detector, You can borrow it from Jim Kraner or the current president.

Dwight Dixon Rev. 10/18/2017


You can subscribe to the NHTSA recall list by going to their website click here and entering Airstream. You will receive notifications of all Airstream recalls.  Less severe problems are handled by service bulletins, but are not available online.

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