maintenance matters
Wheel bearing service–
easy add-on to a brake job.
Wheel bearing service should be
part of your yearly condition inspection
and should be very high on your to-do
list if one or more of your wheels become
submerged in water for any reason,
(unless your whole plane becomes submerged in water, which is an entirely different matter). If your plane spends a lot
of time outside in rainy weather, you also
need to keep especially close watch on
the condition of your wheel bearings. In
any case, water and wheel bearings don’t
mix well. If you are a particularly active
flyer, you should service wheel bearings every 200 flight hours if that comes
sooner than yearly.
KITPLANES® and/or the wheel manufacturer’s service literature, which is available
online. With the wheels off, remove the
retaining clips that hold the inside and
outside bearings and their related plates
and seals in place. Be sure not to mix up
parts from the inner and outer bearings
or between right and left wheels. Clean
each bearing and its related parts one
at a time to be safe. Avgas will work well
for this, but Stoddard solvent is a better
choice for cleaning and degreasing parts
since it is less volatile and has lower toxicity. Any well-stocked hardware store
should carry it. Consult the MSDS for
safety considerations. These should be
available from a retailer selling the product or online. In any case use the minimum amount practical and dispose of it
properly after use. Wear some disposable
First—The Wheels Come Off
To service your wheel bearings you will
need to remove your wheels. This should
be done with an eye towards safety at all
times. Remember that you should never
leave your plane supported only by a
hydraulic jack. Always jack the plane up,
remove the wheel, and then lower the
plane back onto a solid support. If you
don’t have proper jacking equipment
and supports, wait until you do. This is no
place to cut corners or get in a hurry.
To remove your wheels you will first
need to disassemble the brake calipers.
Be sure to release your parking brake first
if you have one. It is also a good idea to
deflate the tire before you remove the
axle nut. For more details on brake disassembly, you can refer to the “Maintenance Matters” article in the April 2014
Dave Prizio
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KITPLANES June 2014
This is an exploded view of a typical Cleveland wheel and brake rotor assembly. The
Grove wheel is very similar, but lacks the center O-ring of the Cleveland wheel. If you
can’t remember where all your parts go, this could come in handy.
Dave Prizio is a Southern California native who has been plying the skies of the L.A. basin and
beyond since 1973. Born into a family of builders, it was only natural that he would make his
living as a contractor and spend his leisure time building airplanes. He has so far completed
three—a GlaStar, a Glasair Sportsman, and a Texas Sport Cub—and he is helping a friend
build a fourth, an RV-8. When he isn’t building something, he likes to share his love of aviation
with others by flying Young Eagles or volunteering as an EAA Technical Counselor. He is also
a member of the EAA Homebuilt Aircraft Council.
www.kitplanes.com & www.facebook.com/kitplanes
This drawing shows support blocks under the hub as the bearing race is pressed out
and a press bushing that just fits the bearing. By using this setup and a hydraulic press,
you will avoid damaging the wheel.
nitrile gloves to reduce skin exposure to
the solvent, and use safety glasses to prevent getting solvent into your eyes.
Clean and Inspect
Thoroughly clean all grease and dirt from
the bearing and the race, and inspect
the race and each roller for pitting, surface deterioration, or any other signs of
impending failure. Any discoloration
that won’t rub off is a cause for concern,
and any damage to the wearing surface
of any part that you can feel is cause for
replacement. After cleaning the bearing
parts, dry them off with compressed air
by blowing parallel to the rollers only.
Resist the temptation to spin the bearing
with compressed air. Spinning the bearing when it is dry can damage it.
Removing and installing the roller part
of the bearing (also called the cone) is
pretty straightforward. Just get a new
replacement part with the same part
number, clean it up, pack it with grease,
and put it in. Do not install a new bearing
without cleaning it thoroughly and packing it with the proper grease. The packing grease that comes with the bearing
is not suitable for your use. Replacing a
bearing race is somewhat more challenging, but not terribly difficult. That said,
there are definitely better and worse
ways to go about it.
To the Races
To replace a bearing race, you first need
to remove the tire and completely disassemble the wheel. Take care to fully
Note the pitting and discoloration on this bearing race. This
needs to be replaced.
A hydraulic press set up to push an old
bearing race out of a wheel. A large
socket proved to be just the right size to
clear the hole in the hub and press on the
bearing. Note the slight gap under the
wheel flange.
deflate the tire and remove the valve
stem before you remove them from
the plane or attempt to disassemble
the wheel. Safety dictates that the tire
should be deflated before the axle nut
is removed. If there is any issue with the
wheel or wheel bolts, you certainly do
not want to find out about it by having
the wheel come apart on you when you
remove it.
With the wheel taken apart, you have
two ways to go to remove the race. By far
the preferred way to remove the race is
with a hydraulic press. A large socket may
work or you might need to find a piece
of round steel stock that is large enough
to engage the race, but small enough to
pass through the hole in the wheel and
push the race out. The exact size may
This bearing cone is beginning to show signs of deterioration
from corrosion. It needs to be retired, along with the race.
Photos: Dave Prizio, courtesy Parker Hannifin Corporation (Cleveland Wheels and Brakes) KITPLANES June 2014
61
Be sure to keep track of and keep clean all your bearing parts as
you disassemble them. This wheel will need to be disassembled
if a bearing needs to be replaced.
vary with the size of the wheel. The other
thing you will need is a solid object on
which to rest the wheel hub when you
are pressing the race out. Do not attempt
to press out the race while supporting
the wheel on its outer flange. The wheel
is not designed to take this stress. As a
distant second choice, you may use a
Try to minimize the amount of solvent you use when you clean
your bearings. It will make for less hazardous waste to dispose of
later. Nitrile gloves will help protect your hands.
drift punch and hammer to tap the race
out of the wheel hub, also while fully
supporting the outer portion of the hub
during the process. When using a punch
and hammer, it is very important to keep
the race moving outward evenly and to
avoid damaging the hub with the punch
or the hammer.
To install a new race, place it into position and then use the old race placed
directly on top of it to drive in the new
race. This may be done with a hammer
or, better yet, with a hydraulic press. The
old race is the perfect size for doing this
job. Again, support the opposite side of
the wheel hub and do not rest the wheel
on the machined mating surface where
the two halves bolt together. This keeps
all the stress in the hub part of the wheel
where it is supposed to be. Make sure the
new race is solidly seated into position.
Replacement Parts
The question often arises, if I replace
part of the bearing do I have to replace
the other part, too? Unfortunately, the
answer is yes. If the race is bad, buy a new
race and a new cone (the part with the
rollers), even though they are sold separately. How about using bearings from a
non-aviation source? If you are an Experimental owner, there is no restriction as
to where you buy your bearings. I would
not hesitate to use a bearing of the same
number if it came from an auto parts
store or a bearing retailer, rather than an
aviation parts supplier. But it is your decision, so do what makes you comfortable.
Place about two tablespoons of grease in one hand and use the other to work the
grease into the bearing cone.
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KITPLANES June 2014
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Before installing or removing a bearing race, be sure to set the
wheel up so that it rests on the hub and not the flange or center
of the rim. Here a block of steel will be used to bear on the hub.
And Now—the Grease
With a new race in place, it’s time to
grease the wheel bearing. This calls for
the question, which grease? There are
at least two possible choices to consider
just among AeroShell products. AeroShell Grease 5 is a good choice for wheel
bearings and is well-priced at $6.85 per
tube for the budget-minded mechanic
who still wants a good product. AeroShell
Grease 22 is a synthetic grease that Shell
specifically recommends for wheel bearings, but it is more expensive at $11.85
per tube. Exxon Mobil also makes a suitable synthetic grease called Mobilgrease
28. It runs about one dollar more per
tube than AeroShell 22. Note: Grove
specifically recommends AeroShell 22,
but Cleveland recommends Mobil. If you
decide to switch grease from one type to
another, you must thoroughly clean off
all of the old grease and replace the felt
seals before doing so.
One thing to consider when buying
grease is the recommendation of your
propeller manufacturer, assuming you
have a constant-speed prop. It makes
good sense to buy one grease that will
serve both purposes. It will also save you
from mixing different types of grease in
your prop, something that Hartzell for
one strongly recommends against.
The actual greasing process can be
messy and a little tedious, but it isn’t
too bad once you get the hang of it.
Take a glob of grease, say about two
tablespoons, in one hand and grasp
If you must, you can use a hammer to carefully drive the new race into
the hub. Use the old race as a driver. The old race also makes a great
driver if you are using a hydraulic press, which is the preferred method.
the bearing cone in the other with the
narrow end facing up. Place your thumb
on top of the bearing and press it repeatedly into the grease until it begins to
squirt up through the rollers. Then rotate
the bearing and do another section until
you have completely gone around the
bearing. While you are at it, apply a thin
coat of grease to the race. It is a little easier
to say than do, but with a little practice
you will get good at it. Low-cost bearing
packers have not worked well for me, and
higher priced ones are just not worth it
for once-a-year use. The hand method
KITPLANES June 2014
63
has the advantages of being well-proven
and extremely cheap. A pair of disposable
nitrile gloves makes personal clean-up
much easier.
Reassemble—and Enjoy!
With the bearings well-greased, reassemble the parts, replacing felt seals and
plates as needed to keep the bearing
protected from dirt and water. After
cleaning, felt seals should be lightly oiled
before being reinstalled. These seals have
the very important job of keeping moisture out of your bearings, so give them
the attention they deserve, and replace
them if they show signs of wear.
Needless to say, be sure to carefully
inspect your wheels and brakes before
reassembling everything. Replace any
worn or damaged parts. Especially look
for any cracks in your wheels. These can
lead to catastrophic failure and send your
plane careening into the weeds or worse.
After assembling your newly serviced
bearings, be sure to clean up any excess
grease, especially off of the brake rotors.
Put all the bearings and seals back together the same way they came apart. Keeping
things as clean as you can will minimize clean-up later.
Reinstall each wheel by tightening the
nut back to its original position. Be sure
to test each wheel to make sure it doesn’t
drag or feel loose. When you are sure
the nut is in the right position, replace
the cotter pin. You are ready to roll for
another year.
For more information about maintaining wheels and brakes, see the manufacturers’ publications available online. And
don’t be shy about calling if you have any
questions. They want to help you do the
job correctly and get long and troublefree use out of their products. J
For more information, visit Grove Aircraft
Landing Gear Systems: http://tinyurl.com/
k63r2lt or phone 619-562-1268. Cleveland
Wheels and Brakes: http://tinyurl.com/
n6v775t or phone 800-272-5464.
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KITPLANES June 2014
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