This information applies to the model of BMW from late 1955 through 1969 and are
R26, R27, R50, R60, R69, R50/2, R50S, R60/2, R69S, R50US, R60US, R69US, /5, /6 &
/7 models. The "US" and post 1970 models have telescopic forks and this
article only applies to the rear swing arm.
BMW used tapered roller bearings in the swing arms on the series from late 55
through 69. That bearing only rotates through a small portion of a circle. The bearing life under that condition is very short. It is a very poor use
of that bearing. It is the best solution to the problem however. The
BMW /2 swing arm bearings will last a long time if lubricated often and the
preload is about correct. See below.
Setting the preload on Earles forks
The BMW motorcycle factory service manual leaves out some information and the
result is unclear. This is my attempt to explain it.
The preload on the /2 front BMW swing arm is designed to be set by a
combination of the shims and the torque on the swing arm axle. These shims
look like a thin flat washer. We just put in the thickest ones that we
could get in.
It is natural to ask which side gets the most shim. By moving the shims
around as much as possible, one can move the swing arm from side to side a bit. The maximum amount is about one millimeter or .040." That is nothing. If
you had the room to move the wheel plus or minus 1/8" inch you would still be
just fine. In other words, it matters none if all of the shims go in one
side or they get split up somehow. We always split them up about evenly.
Do not be concerned about wheel "alignment" as such.
BMW provided shims in .5 mm (.020") increments. They want you to be
able to shim it down to almost nothing. If one shim is too loose and the
next one can't be installed because it is too tight, what does one do? BMW
didn't think this one out very well. Stuff as "thick" of shims in as you
can get in. The last one may have to be gently tapped in place. If
they go in very easily, then they aren't thick enough. Get the next size
At BMW of Marin we had a variety of sized shims to choose from, so it was
easy. Tighten up the axle, but there is no such thing as a correct torque
number. When the swing arm axle, or pivot pin, is set too loose, you can
feel play in the swing arm bearings. As you tighten the axle up, the play
will go away. In theory, when the play just goes away you have zero
preload. It should occur when the axle has some amount of reasonable
torque. It would be nice to see torque between 10 and 40 lbs. It
wouldn't really matter if the torque turned out to be 5 lbs at zero preload,
because the nut on the other end locks it in place. It won't fall off or
change adjustment. If your shims are not thick enough you may have to use lots of torque to get to zero
play. You are now bending the two castings inwards. That is not
good. They are being pulled together against the curved cross piece just
above. If your shims slid in too easily, I would be concerned.
The axle could have three conditions.
1. Too loose and that leaves the bearings loose, they will eventually
fail and it may handle poorly.
2. Exactly no, or very little, preload and that will give maximum life.
3 Too much preload, and that will ruin them even faster than condition 1 or
One can easily tighten the preload adjustment bolt too far one a rear swing
arm and cause the box
section of the frame to bulge out. That is too much preload and the frame
will take a "set" in the bent position.
Removing and installing the BMW motorcycle /2 front swing arm axle and
Remove the front wheel to lighten up the swing arm. I suggest also
removing the fender, as it can only get in the way and possibly get damaged.
(Swing arm shown in the sidecar (forward) position.)
Left side is the locking cap (nut)
Right side is the axle
The right and left side of the swing arm axle looks about the same. The
left side is actually a lock nut. Remove it first. Then back off the
axle head on the right side. Be sure to use a 12 point box end wrench or
socket. Apply pressure carefully and avoid "rounding off" the flats. It should back out, however sometimes the axle is rusted in place. Use
your favorite penetrant to soak for hours/days until it can be broken loose.
Once the swing arm axle is out, the swing arm will fall or wiggle out. Remove the seals to inspect the bearings.
They are almost for sure going to be bad.
Three common ways to remove the old bearing cup.
1. Use a puller. Ed Korn makes a good one at a reasonable price. Kukko makes a
very expensive one.
2. Weld a bead on the bearing surfaces and they will cool, shrink and
fall out. Keep the "shrunken" cups to assist in the installation.
3. Use a Dremel tool to cut through the race and it will come out in
pieces. This is the hardest method, but it may be the most convenient one.
Before you replace the bearings, clean out the large tubing well. If
you have a pre 65 swing arm, it will have no way to lubricate the bearings. See below. Decide how you want to proceed with adding in a grease zerk, or
not. Be sure to replace the seals.
First, leave the swing arm aside and try the axle in the down
tubes. Clean the axle and holes very well. Use a lube to assist. See if it easily threads into the threaded hole. If not, take
a look through the casting and see if the axle is centered. One, or both,
castings (ears) could be misaligned. Even an amount of
misalignment that isn't visible may be enough to cause trouble with getting the
threads to start. Often they were a "bit off" when new. That is why a
tool was used to help "pull" it in. If it goes in freely, you are very
lucky. A previous owner could have messed up the axle threads while trying
to install it. Check the threads carefully to see if they are messed up. A metric thread file will clean them up. I also understand that an axle
made out of stainless steel is available. A new axle may be easier to find
and cheaper than a metric thread file.
If you look at the threaded end of the axle, you will see a smaller threaded hole. That threaded hole is for a puller. The axle easily goes into the
right side, but when the axle gets over to the left "threaded" side, it may be really hard to get it
started into the threaded (ear) casting. If you have a "helper" then
you may not need the puller. One person pushes on the axle while the other one turns it. The "push" is accomplished by the helper sitting on the floor and grabbing the
fork by hand and shoving with a shoe. This way one can get decent the
"push" needed. If that doesn't work, then you need a puller.
Make a puller "tool" to install the swing arm axle on Earles forks.
The puller adds some pressure to "encourage" the threads to start. You
could buy the tool from Ed Korn, but you may only use it once. Here is how
to make a simple tool. Find a long bolt that fits into the threaded hole
in the swing arm axle. I can't remember the size
now, so please email it to me, thanks. Get the swing
arm axle all of the way up to the left side where it is not wanting to thread. Now install the long bolt in the small hole. Run the bolt in all the way
by hand. Now
measure the extra amount needed on the shank of the bolt to "fill up" with washers or
a socket. You want the head of the bolt to apply pulling pressure against
the casting and that will "pull" on the axle a bit. Do not add much torque
to this puller bolt. If you pull too hard, you may damage the very threads
that you are trying to get started. It shouldn't take very much "pull" to
allow the threads to start. Now turn the axle a bit. You should see
the axle "move" as it starts threading into the casting. One
sort of needs to turn the puller a bit and then the axle head a bit. In a
rare case, you may need to go back and forth a few times to get it started.
Greasing the /2 BMW motorcycle rear swing arm
In 1965, BMW added the ability to grease both swing arms. On the rear they drilled a hole, in the middle of the two existing holes for
adjusting the bearing tension, all of the way through. One day, in about
67, I collected all of my salvaged adjusters and drilled them out. From
then on I swapped them any time I replaced the bearings. I went one step
farther, I drilled, tapped and installed an American nipple to one of the
aluminum caps. On every service we would remove the original cap and hand
screw ours on, just to grease it, then put the original one on. Now we can
get the chainsaw type gun. There is no downside price to be paid for
adding the hole. On a show bike the "new hole" can't be seen by judges.
This is a photo of the rear swing arm adjuster with the aluminum cap removed. You can see the lock nut that is around the adjuster. The adjuster has
three holes in it, two larger ones and a small one in the center. The
center hole was added in 1965 for adding grease to the bearings. The older
adjusters had only the two holes for the tool to adjust the swing arm bearings.
How to lube the front swing arm on a /2 BMW motorcycle
BMW added the front swing arm nipple at the same time that they added the
hole to lube the rear. On the pre 65 Earles forks, where we added a grease
nipple, we did it a bit differently. The BMW nipple required a special
type gun and was off center. Both were easy to overcome in the shop, but
not so easy for the owner who does casual maintenance. The off center
nipple made it so that the resistance to the far side, the right side, was too
great for it to get grease. The grease would squeeze out the left side and
never get to the right side. The solution is to grease until it squirts
out of the left side, wrap small diameter rope around where the grease comes
out. Pull the rope tight and that sort of stops the grease from coming
out. This added resistance is enough to force the grease to go over to the
right side and lube that bearing too. Each of my mechanics had a "greasy
rope" on his tool cart.
I would solve both problems by adding an American nipple to the bottom of the
front swingarm. That way it was out of sight, out of the way of punching a
hole in the front cover and had equal resistance to both bearings. It
wasn't "original", sorry. In the 60s we didn't realize that they would
ever become a collectors item. We just modified them.
The only disadvantage of greasing the swing arm this way is that one must
pump the entire tube full of grease. This is not a problem if the swing
arm gets greased frequently. It really should get greased a few times a
year to clean out any dust or water that could get in past the seal.
Another way to solve the grease requirement
The washer is on the left and a shim on the right
The washer on top of the race
This is perfect for the owner of a pre-65 BMW who prefers not to add in the
grease zerk mentioned above. This makes it no maintenance modification. Adding in these washers makes it similar to a "sealed" bearing. This is
not as good as being able to add grease often and push out the old dirty grease.
One can put a washer under the cup to seal it off. BMW didn't do it
that way, but it will work very well. The washer is barely larger than the
swing arm axle. That keeps the grease in place. The seal on the
outside keeps it in on that side. The washer is available from Joe
Groeger. You will need two of them. They are stainless steel, so
they won't rust. He also has the shims in stainless mentioned above. They come in 1 mm, 1.25 mm, 1.5 mm, 1.75 mm sizes. There is no way to know
which or how many you will need. If you want to be safe, order two of each
See some of the tools that can be used to
grease your BMW
Checking the /2 BMW motorcycle drive shaft bolts
It has come to my attention that BMW owners are still having the driveshaft
bolts fall out of the output flange of the transmission. I am sorry for
"assuming" that everyone knew about the propensity of the /2 driveshaft bolts to
fall out. The /5, and later, seldom had this problem, but it happened
It is very easy to test for loose or missing driveshaft bolts. It is
non-invasive and takes 10 seconds. This test should be performed at least
yearly. Put the bike on the center stand and in neutral. Use the
index finger of your right hand to push into the boot at the rear of the tranny. Use your left hand to turn the rear wheel. You will feel the bolts "bump"
your finger. If they are finger loose and you are very good, you can feel
it. If one is missing already, it is obvious. This was a required
test before any /2 was admitted into our shop for any work of any kind. It
was a standard part of our "safety test." If a bolt is finger tight, but not
loose, this test won't find it.
They only fall out when improperly installed. This is one place where you need to really tighten
something on a BMW.
If you are apprehensive about them it is very easy to check for tightness. Loosen the front boot clamp. Pull the boot off of the transmission rear
expose the bolts. Use your right knee on the rear brake pedal to hold the
wheel in place. Insert your cut-off Allan wrench (a 12 point 10 mm box end
wrench on the newer bolts) and tighten the exposed one. Rotate the wheel a
bit till you get to the next one and repeat until all 4 are really tight. A normal length Allan wrench won't fit and you wouldn't want to use it anyway. The torque would tend to twist it sideways and damage the gripping surface.
The hex hole would get "wallowed out" quickly.
This is a "long" 6 mm Allan wrench that has the short end cut
off a bit to fit.
Replace the hard to tighten Allan head bolt with this easy to tighten 12 point bolt. A standard
10 mm box end wrench fits it. This bolt came in two versions; long with a washer
and short without the lock washer. Both work OK. Make sure that it
isn't too long and goes through so far that it hits the aluminum rear cover and
binds up the output shaft.
Replace the boot any time that you have it off or loose. It is cheap.
Removing the lock nut on the /5 and later swing arm adjuster
The /5 and later swing arm adjuster has a lock nut on it. Most standard
27 mm sockets are too thick to fit in the space. They need to be turned
down or ground off a bit to fit.
The lock nut is very thin. Sockets have the inner bevel to help guide
the socket into place. This nut is so thin that it is very easy for the
socket to jump off and start rounding off the corners of the nut. Grind
off the beveled part of the socket so that the end is square. In the worst
case one can add a bit of valve grinding compound to the socket for a really
good grip. A modified socket can be purchased from
Joe. I have examined
his tools and they are a very good value. Tell him I sent you.
This is a picture of the tool that Joe sells for $9 plus
How to adjust the swing arm for wheel alignment
I disagree with the recommendations by BMW about this procedure. I feel
that BMW has one over tighten them, or another way to say it is "too much
preload." The apply some small torque only applies if the bearings are new
or in good condition. Even then, I far prefer to adjust them so that all
of the play is gone in the swing arm. If the bearings are even slightly
notched, then does one torque them at the tight spot, or the loose one?
Clearly that is nonsense. Once you have the adjuster just tight enough to
remove all play, then tighten down the locking nuts. The adjuster may need
to be held while doing this.
First off, for tracking and handling reasons, the swing arm adjustment may be
anywhere in the range and few riders are sensitive enough to tell anything.
That mm or two will still allow the bike to go totally straight with hands off.
Keep in mind that the wheels are still in parallel planes. A
bent frame easily shows up in tracking when the
two planes are not parallel. My website has the info on how to check it.
From that standpoint, there is no real reason to be concerned with the
spacing. I know that some will dispute my assertion, but show me the
proof. I have done it. On one bike that I had just assembled the
swing arm with new bearings and seals, I decided to play a bit. I moved
the swing arm fully to both sides and test rode it. Nothing changed.
Some of you have ridden chain drive bikes. The rear wheel alignment
marks are there to get the wheel going straight with the front one. Think
about all of the times that you were riding behind someone with a chain drive
bike and could visually see that the wheels were not in line. While the
bike will handle differently in a right vs. left turn, the straight ahead
tracking is OK until the wheel gets really out of line. Those are huge
variations compared to the minimum adjustment allowed by the BMW frame.
More proof is that I hear from "those that know" that the later BMW models
don't track straight from the factory. That does not contribute to bad
handling or wobbles. The swing arm adjustment is not super critical for
handling at all. Don't obsess over using calipers to get them exact.
Your eyeballs are good for a few thousandths, live with it and be happy.
Far more important is to have the bearing preload just enough so that the play
is gone and that you grease them several times a year. More info on my
There is one thing to be concerned about. That is the driveshaft
alignment in the swing arm tube. The front of the driveshaft is held in
one place by the transmission output flange, while the swing arm can move
around. If the driveshaft is over to one side a bit, it can rub against
the inside of the swing arm tube. This will happen during the upper and
lower travel of the swing arm. I sometimes found a polished ring around
the driveshaft where it had been touching. In one case the symptom first noticed
was a broken driveshaft. Yep, worn so much that it finally gave way and
snapped. The rider reported that it made "gun shot" sound when it parted
and then a lot of banging until he came to a stop.
The reason a driveshaft would rub is due to a bent frame. Frames can be
bent in many ways. The most easily noticed is when the bike fails to track
straight with hands off. A few riders don't notice even when it is severe.
By severe I mean that one must "lean" about a foot to one side to go in a
straight line. Riding a bike like that for an hour on the freeway and I
get sore a back and shoulders.
A frame can be bent in other ways and be far harder to discover. A
fairly common "bend" is in the box section just behind the battery. They
get cocked out of square. This is what causes the driveshaft to touch the
swing arm tube.
This can happen in two ways. First off, not all were straight from the
factory. The quality control on frames in the /2 days was poor. BMW was
lucky to get them within a 3" range of lean for tracking. I have ridden a
few that were even worse. My roommate in 1965 picked up a foreign delivery
R69S from the factory. It was so bad that he took it back and complained.
They tested it and said, "Come back in two days." He did and they had
straightened it and it tracked perfectly. I know it had to be really bad
because he was unable to detect much of anything wrong with his motorcycles.
They are more commonly bent in the box section from an accident. If the
driveshaft is "off" and the swingarm is centered, then suspect a crash.
Further evidence is checking the rear cover of the transmission where the rubber
boot mounts. It is common for the frame to flex enough for the output
flange to knock out a bit of the aluminum. I have seen this many times. It
is one of my regular inspection places during an appraisal. In a "worst
case" crash, we had one bike so badly hit from the side that the output shaft
was broken inside the transmission. About 1/2 of the rear cover mounting
place for the rubber boot was broken out. The box section was quite bent
by visual inspection.
In cases where the "bend" is not so much, it is far more important to have
the driveshaft centered than the swing arm. It is not as easy to center
the driveshaft as it is the swing arm. Best is to have the shocks
loose/off so that the swing arm can be dropped to full extension. Then you
can see an error more easily and adjust accordingly.
In one case, the owner was quite handy and moved the engine over a bit.
He changed the spacers on the left side and had added some spacing on the right
side. While not exactly the BMW way, it worked just fine. Even with
a slight shift of the center of gravity, the bike still tracked OK.
I suggest checking to see if the swing arm and driveshaft both center with
the same adjustment. Once you know that, then you can just adjust the
swingarm by eye and know that the driveshaft does not touch. If you do
have an accident and the bike "goes straight" don't relax until you check the
driveshaft. The "falling over" accident usually doesn't get the side force
necessary to bend the frame at the box section.