This page is about the BMW motorcycle models R50/US, R60/US, R69US, R50/5,
R60/5, R75/5, R50/6, R60/6, R75/6, R90/6, R90S, R60/7, R75/7, R80/7, R100/7,
The Earles fork steering bearings
The original steering bearings are simple ball bearings. They would
wear and have a notch in the straight ahead position. The bearings had to
be adjusted fairly often if one wanted them to last. A modification to
tapered roller bearings is now available.
I highly recommend it.
BMW came out with telescopic forks, for the second time, in 1968 on the "US"
models. The identical forks, with gradual improvements, were used on the
/5 series and later. In 1972, BMW improved the system for adjusting the
bearings. It was a great help. It is highly recommended that an
owner of the 68-71, change to the later system. It only requires obtaining
one part and it is probably still available from BMW. To discuss these
bearings, one must treat them by the style of adjustment and the style of
Type of steering bearings
The 68-69 year models with telescopic forks (part of the /2 series) are often
called the "US" models. They have old style ball bearings. While the
system is exactly the same as the Earles forks, the bearing races are slightly
different. The US ball bearings didn't last very long and were also hard
to adjust. Replacement of the US bearings can be done with tapered roller
bearings, similar to the /5 type. They are superior to the ball type.
You may know them as "Timken bearings" for one of the most famous companies that
The tapered roller steering bearings are the best type available for this
motorcycle application. However, from the standpoint of the tapered
bearing, the application is a very poor one. This "poor" application
applies to the swing arm too. The tapered bearing is designed to carry a
large load at some rpm. You could hang 1000 lbs on the shaft supported by
these bearings and spin it at 1000 rpm and they would last billions of
revolutions. In other words, "forever." A specific engineering
calculation, as an example, is available on my page on wheel bearings.
As motorcycle steering bearings they never complete more than 1/4 of a full
turn. During most riding they only experience a few degrees of rotation.
They also are subjected to every bump in the road while the rollers are in the
same spot. Those bumps are "hammering" the bearings while they are in only
one place. Eventually the bearing races get notched in the "dead ahead"
position. The typical symptom is that at 20-30 mph the bike seems to
"hunt" or "wander" around a lot. It is similar to the steering damper
being tightened up too much. Change the bearings.
This job isn't trivial for the telescopic forks,
refer to my page on "fork alignment" for more
Types of adjusters
The early ones, 1968-71, have an adjustable split collar and the later ones
have a standard locking nut. You will see both and how to adjust them correctly.
1968-71 Split collar and locking clamp
The idea is to loosen the locking clamp, adjust the split collar and then
tighten the locking clamp. It isn't so easy to do and end up with an
adjustment that will assure long life of the bearings.
The split collar system is the hardest to adjust because the initial
adjustment of the collar is changed by tightening the locking clamp around it.
The split collar has 4 holes (not shown) in the side. The holes are for a
tool to be inserted for turning. As one turns the split collar to tighten
the bearings, the gap spreads apart somewhat.
Think of a nut and bolt. The nut is loose on the bolt and can be
wobbled slightly. It could also be moved up and down on the bolt, but by
an even smaller amount. The steering stem is the "bolt" and the split
collar is the "nut." With only those two parts they have some "play." The "nut"
will wiggle on the "bolt." Back to the actual parts. If one now tightens
the split collar, it will spread the gap apart more and the "play" increases.
Some of it's tightening gets translated into tighter bearings and some into
"spreading" the collar.
Later, when one is happy with the bearing tightness and then tries to lock
the collar into place with the clamp, it squeezes the collar and reduces the
gap. This tightens the bearings even more than the initial setting.
When the job is finished, the bearings are too tight. That accelerates
notching even faster.
Old system, in place on the steering stem.
So, how do we do it? Since tightening the locking clamp tightens the collar,
we must leave the collar "loose" by just the right amount so that when the
locking clamp is tight, it is all perfect. Does that sound like a lot of
trial and error? It was, until we discovered a trick. Once the collar is
near the correct place, but still a bit loose, tighten the locking clamp.
Now the whole thing can be turned as unit. Rotate them both to get the
desired adjustment. The locking clamp may hit the handle bar mounts.
The locking clamp needs to be loosened to move it a bit, so that it can be
rotated and not hit the handle bar clamps. You will find this to be faster
and more accurate than doing it the way that it was engineered by BMW.
The system from 72 on
This is the "improved" locking nut that has no split. This type should be used
to replace the older (1968-71) split collar system. On this one, just tighten it to
zero play and tighten the large nut above the upper triple clamp plate.
Tightening down the locking nut on top of the triple clamp adds in just enough
pressure to be about right for the desired pre-load. The 4 notches around the edge have replaced the 4 holes of the older system.
A tool, supplied in the tool kit, is made for reaching in and hooking onto one
of the notches. Many just reach in with a punch and hammer it to the
desired place. That just bungs up the square edges.
Maximum bearing life
For maximum steering bearing life one must satisfy a few conditions.
1. Keep it lubricated. Some owners have modified the stem to
allow greasing with a grease gun. I have never done it.
2. Keep it clean and do not allow high pressure soapy water to be
forced in while washing it at a commercial car wash.
3. Adjust it to the correct amount. The longest life of a taper
bearing is with a tiny bit of preload. That means to tighten it to some
small amount beyond the point of no free play. How much is the
question. If you have just replaced the bearings, I suggest that you over
tighten the bearings and then back off to what you need. This will help
assure that they have seated properly.
In either case, the correct tightness is so that no free play exists.
Free play is hard to detect accurately while the bike is sitting on the
centerstand, but one can get close. Just grab the lower fork legs
(castings) from the front and pull towards yourself. If you still have the
adjustment loose, then you can feel the play. Have your friend slowly
tighten up the adjuster while you are checking the play. You may be able
to get it really close, but don't be discouraged if this doesn't work for you.
My highly experienced mechanics sometimes had trouble getting it exactly right
the first time by this method.
Once the bike is together, you may roll it forwards and gently apply the
front brake. If you feel a tiny click or movement, that is the play.
Free play will be noticed by a shimmy, or shudder, in the front end while
applying the front brake. It is possible that a shudder is really a brake
drum that is out of round, see below. Extreme over-tightness will be
noticed by the forks not swinging totally freely while the wheel is in the air,
such as on the center stand. It will be similar to some tightening of the
steering damper. There is some amount of tightness between perfect and the
extreme. I can't tell you how to detect that situation. It can be
avoided by tightening only to "no free play" and then
tightening the large nut properly.
Note. You can find another way of setting
the preload on the steering bearings by one of the well respected experts of
BMW. Basically it is to adjust it tighter until the forks stop flopping
from side to side and just gently fall to one side. We found a variable in
that procedure due to the weight of the lube, temperature of the lube, routing of cables, hydraulic lines and wires that
would affect the resistance to falling to one side. This "falling slowly
to one side" is not reliable.
It is usual for the steering adjustment to "seat in" after riding a few
hundred miles, so check it often. We always asked our customers to come
back after several hundred miles for a free adjustment. Readjusting once
is usually enough, but keep checking it anyway.
It is very easy to test for an "out of round" brake drum, or warped disc.
With the bike on the center stand and the front wheel in the air, give it a
spin. Gently squeeze the front brake lever. Hold it at the point
where it gives the slightest amount of braking. The wheel should slowly
come to an even stop. Keep the brake lever in one place, gently turn the
wheel by hand and it should not have a "free place" and then a "tight place."
If the drum is "out of round" then the shimmy caused by that can be easily
confused with one caused by loose steering bearings.