Bearings question

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buckle823

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May 16, 2006
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Michigan
Is it true that bearings will "flatten out" if the Rv sits in one place for an extended period of time? This sounds bogus to me. I can't imagine hardened steel "flattening out" from the weight of a travel trailer on 2 axles.
 

Lowell

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Tempe, AZ
buckle823 said:
Is it true that bearings will "flatten out" if the Rv sits in one place for an extended period of time? This sounds bogus to me. I can imagine hardened steel "flattening out" for the weight of a travel trailer on 2 axles.

That's a new one to me.  The bearings won't go flat but it is important to have the bearing repacked occasionally.  I have our TT bearings repacked once a year.  I also found it pays to shop around for the service.  Some places wanted $150/axle plus cost of seals.  My TT dealer did it for $75 an axle plus cost of grease seals.  I should do it myself but I wasn't ready to tackle it this time.
 

John From Detroit

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I will second that, Bearings are made of the finest steel, and are big enough that they won't flatten out if you put a 2nd rv on top of your Rv and let it set for 10 years or more

However they do dry out and require re-lubrication, and once they dry out they "Flatten" very quickly.

TIRES, on the other hand.  are another issue, one which needs attention from time to time.

Tires need to be used or they go bad super fast  Same for assorted engine seals and the like both in the main engine and the generator
 

bross

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Pennsylvania
There is a danger of bearing damage from leaving any bearing sit for extended periods of time in one position but it is not because the bearings flatten out. The damage is caused because the rollers on the top half of the bearing are not loaded and free to move within the clearance of the bearing. Over time, natural frequency vibrations cause these unloaded rollers to mark the surface of the bearing races where they have been resting.  These marks on the races are the beginning of bearing failure and will get steadily larger once you start using the bearing. This is a common problem in industry where standby back-up equipment is used. Keeping the bearings well greased and rotated occasionally will slow the process.
 

172ndLIB

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Dec 11, 2006
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I have never seen bearings flatten out but I have found that gravity will affect the grease.  I repacked the bearings on a trailer that sat for 5 years and most of the grease had settled to the bottom of the housing.  Grease can thin with age and flow easier.  Some like lithium grease actually thickens and turns into a waxy substance.  Either way its bad for the bearings.
 

rbell

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Sep 29, 2006
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Jackson, Michigan
That sounds like an old wives tail to me also. I know the grease they recommend has changed a lot over the years. It used to be thick and stringy like stuff and it's not any longer. The Dexter Axle site has some good reading about that stuff and they make a living building axles.
The tire advice is good.
 

kbfeip

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Dec 24, 2006
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Discovery Bay, CA
The grease is designed to "bleed", this is the effect you are seeing from setting over time.  Bleed rate is the amount of fluid lubricant (oil) that a grease releases from the thickener system to do its job...that is to provide a hydrodynamic film of oil to separate the rotating surfaces.  The thickener in the grease only holds the lubricant, and releases according to the bleed rate formulated for the grease.

Consider the amount of fluid often present at the top of a new cartridge of grease off the shelf.  This is simply normal bleed, and the oil can just be stirred back into the grease for use.

Relubrication needs to occur to replenish grease which has not only been subject to "duty", but also to replace that which has bled out in normal use and over time.
 

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