by Richard Kaye
Skater's Edge
BEARING NECESSITIES
When you're pumping the ramp or pushing down the street, ball
bearings are probably not the focus of your thoughts. In terms of board
performance, however, bearings could be considered the most im-
portant part of your set-up. If they're screwed up, you're not going
anywhere, pal, so pay attention to this column.
Ball bearings have been around for cen-
turies. When the ancient Egyptians built the
pyramids, they rolled the large stones over
logs-a crude ball bearing set-up. As early
as the 1500's, Leonardo Da Vinci made
detailed sketches of ball bearing systems
The first commercial use of our little round
friends occurred in New York City during the
mid 1800's. The town was full of bicycles
which used bushings (a metal axle through
a softer metal core). These vehicles had
massive wobble problems, and there were
too many accidents, so bearings were in-
troduced to increase stability. Since that time
the ball bearing has seen numerous ad-
vances in design and manufacturing.
Although they've been around a lot longer,
sealed bearings weren't put into skateboard
wheels until the mid-70's. Before that time
skateboard wheels used to have a "full com-
plement" bearing system. Loose bearings
were put on both sides of the wheel and held
into place with cone nuts and washers. This
design was defensless against dirt and a
loose nut would cause all of the bearings to
just roll away. They were a constant hassle.
Bearing technology has advanced greatly
since then. Materials such as stainless steel
and Teflon along with computer controlled
fabrication machinery have produced a
much better product than just a few years
ago. But how do you measure "better" and
what does it mean to skaters?
The first step is to understand the word
torque. Torque is a force that produces or
stops rotation. Think of any wheel with ball
bearings at the center. If you spin this wheel
and measure how long it takes to stop, you
get an idea of torque. If the bearing has high
torque, the wheel will stop quickly. If the bear-
ing has low torque, it might spin for hours.
Lower torque means your board will roll
farther and faster. To measure torque exactly
we can use a mathematical equation
developed by Sir lassac Newton, T-la,
28
which takes into account the size of the
wheel), and how fast it stops(a). But what
causes torque to be high?
The factors that affect torque the most are:
1. Dirt Specs of sand and dust can enter
a bearing and increase torque. Rubber seals
are a way to help keep dirt out but they rub
against the race as it tries to turn and cause
high torque. Metal shields don't keep the dirt
out very well, but they allow the bearing to
spin more freely. Teflon seals combined with
a groove in the race keep out more dirt and
cause less drag.
2. Lubrication-The type of lubricant is also
Important. Heavy grease, stock on many
GMN and NMB bearings, can actually slow
you down. Most light oils work just fine to
keep torque low without a lot of bearing wear,
but only if kept clean. Use a synthetic motor
oil mixed with a Teflon-based lubricant for
best results.
3 ABEC-Bearings are produced with a
variety of machines to a variety of tolerances
Ball smoothness and size as well as inner
and outer race is judged on a scale of one
to nine and given a rating called the ABEC
(American Bearing Engineering Committee)
number. One is the poorest quality and nine
is the highest. Naturally, the higher the
number the higher the cost. GMN and NMB
bearings sold at your skate shop are usually
ABEC1. An example of a bearing with
ABEC 9 would be the gyroscopic instru-
ments in an airplane, where faulty equipment
means death.
4. Retainer-Balls in most precision bearings
are kept apart by a retainer or separator.
Without a retainer there would be contact and
rubbing between the balls which also causes
an increase in torque. The GMN use a
Phenolic retainer with lower torque than the
steel ribbon used in NMB's
5 Material Most ball bearings today are
made from a hardened chrome alloy steel
#52100. There are several other alternates
available, one of which is stainless steel,
#440C. The stainless steel doesn't rust, so
you can easily clean your bearings with soap
and water, then re-lube them. This can ex-
tend bearing life and quality indefinitely.
To accurately measure the RPM vs. torque
characteristics of bearings with a variety of
shields and lubricants, a bearing test fixture
was developed. To go into the intricacies of
the test procedures might be a little technical
for the average four wheel drifter. After all,
most skaters change bearings only when
they change wheels, about every couple of
months. In between sets of bearings you
should follow at least a light maintenance
schedule.
Despite what your friend who "knows"
says, use spacers between your bearings in
each wheel. Even the hardest urethane can't
make up for the stability that a spacer
provides.
When you change your bearings, don't
strong arm the wheel nuts. Snug 'em up firm
to get a good bearing seat, then ease each
nut back about half a turn until the wheels
are slightly loose and spin free.
When your bearings rust to a seizure, don't
shower them with WD-40. It's a short term
solution. Your wheels will spin again, but the
bearings will dry out soon, the noise will
become unbearable, metal shavings will
appear, then you'll have full metal break-
down. There are better ways to rehabilitate
a rusted set. Take the bearings out of your
wheels and remove one seal on each. Blow
out any sand and grit that may be living in
there. Massage in a little Tri-flon or Speed
Cream until they spin again and are fully
lubed. Reinstall the set with the sealed side
facing the elements.
We could also go into that cautionary
finger wagging like "don't ride through the
water" and "don't ride in sand," but we don't
want to put the clamp on your fun. Just
remember that your your bearings are always
faster when they're clean. The longer they
remain that way, the longer they last.
Hopefully we'll see some affordable stainless
steel bearings soon. They should last much
longer than the rustable kind. In the mean-
time, keep on rolling!
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