31 BMW 1977 R100RS Replace Steering Head Bearings, Rebuild Front Forks

I show how to remove the forks and steering stem in this write-up.

The procedure for replacing the steering stem bearings and rebuilding the front forks is the same as for the 1973 R75/5 project. On that project, I borrowed the BMW steering race bearing puller. On this project, I used the Cycle Works bearing puller.  You can review the procedure here:

Parts

I got new steering stem bearings, the lower bearing dust cap from Cycle Works and a fork rebuild kit from Tom Cutter, Rubber Chicken Racing Garage.

Part # Description                                           Qty
#FOH-1-B Rebuild Kit
(Tom Cutter, Rubber Chicken Racing)
1
07 11 9 985 070 TAPERED ROLLER BEARING – 28X52X16 2
31 42 1 234 509 RING (Bottom Bearing Dust Cap) 1

Tools

I bought the steering head bearing puller tool set from Cycle Works. You can buy both tools as a set, or each individually.

  1. (Cycle Works Steering Stem Bearing Puller).
    This tool removes the inner bearing races from the top and bottom of the steering head.
Cycle Works Steering Stem Bearing Tool-Outer Race Puller Plate Parts

Cycle Works Steering Stem Bearing Tool-Outer Bearing Race Puller Parts

Cycle Works Steering Stem Bearing Tool-Outer Bearing Race Installation Tool Parts

Cycle Works Steering Stem Bearing Tool-Outer Bearing Race Installation Parts

2. Cycle Works lower bearing race removal tool.
This removes the inner bearing race at the bottom of the steering stem that sits just above the top of the aluminum triple clamp.

Cycle Works Steering Stem Lower Bearing Puller Tools

Cycle Works Steering Stem Lower Bearing Puller Tools

3. BMW Fork Damper Rod Oil Control Ring Compressor
This simple tool compresses the oil control rings on the top of the fork damper rod so it’s easy to insert the rod into the fork tube and not damage the rings. You can order this from you BMW dealer (part# 83 30 0 401 938). It cost about $35.00.

BMW Fork Oil Control Ring Compressor

BMW Fork Oil Control Ring Compressor

Inspect Steering Stem Bearing Races

The outer races show vertical bars which is a sign of brinneling. This is when the tapered rollers slam into the outer race repeatedly. This hardens and deforms the outer race which results in notchy steering. If the bearing grease is not refreshed, it gets squeezed from between the roller and the outer race so metal to metal contact occurs. So, it’s time to replace the steering stem tapered roller bearings.

Steering Stem Outer Race Shows Brinelling

Steering Stem Outer Race Shows Brinelling

I use a hammer and a wood block on top of the steering stem to drive the stem out of the frame. I hang on to the bottom of the stem so it won’t fall out and hit the floor. Here is the stem with the top bearing resting on the top of the stem.

Steering Stem Removed

Steering Stem Removed

I clean up the lower triple clamp and polish it.

Cleaned and Polished Lower Triple Clamp

Cleaned and Polished Lower Triple Clamp

I had the frame powder coated with the old outer bearing races in the frame. I thought this might reduce the opportunity to get powder coat on the new outer bearing races.

Old Steering Stem Outer Race (Some New Powder Coat on Top)

Old Steering Stem Outer Race (Some New Powder Coat on Top)

Assemble Cycle Works Bearing Tool and Remove Steering Stem Outer Races

The Cycle Works steering stem bearing puller has several parts that are assembled to pull the top outer bearing race.

Outer Bearing Race Puller Parts

Outer Bearing Race Puller Parts

The tapered gold colored ring fits on the end of the large bolt with the smaller tapered end against the undeside of the bolt head.

Outer Race Puller-Tapered Collar

Outer Race Puller-Tapered Collar

Outer Race Puller-Tapered Collar On Puller Bolt

Outer Race Puller-Tapered Collar On Puller Bolt

The gold sleeve has a cut-out on one side and fits on top of the tapered collar with the cut-out end on top of the tapered collar.

Outer Race Puller-Gold Sleeve

Outer Race Puller-Gold Sleeve

Outer Race Puller-Gold Sleeve

Outer Race Puller-Gold Sleeve

Outer Race Puller-Gold Sleeve Orientation on Tapered Collar

Outer Race Puller-Gold Sleeve Orientation on Tapered Collar

The large nut goes on the bolt against the sleeve. As this is tightened it spreads the tapered collar so the edge slides under the edge of the outer bearing race.

Outer Race Puller Puller Assembly

Outer Race Puller Puller Assembly

I place the assembly in the top of the steering head. The tapered collar needs a couple light taps to pass under the bottom of the upper steering stem outer race. There is an audible “click” when it is below the race.

Tapping Puller Assembly Past Outer Bearing Race

Tapping Puller Assembly Past Outer Bearing Race

I tighten the puller stem and large nut to expand the tapered collar. I can feel when the tapered collar expands under the race and moves it upward a small amount.

Tightening Puller Bolts to Expand Tapered Collar

Tightening Puller Bolts to Expand Tapered Collar

I put some grease on the top threads of the puller bolt. I put the larger collar on top of the steering stem and then the cover with large nut and tread this down on top of the large collar.

Greasing Puller Bolt Threads

Greasing Puller Bolt Threads

Sleeve of Outer Race Puller Fits on Steering Stem

Sleeve of Outer Race Puller Fits on Steering Stem

Outer Bearing Race Puller Cover-Nut On Puller Bolt

Outer Bearing Race Puller Cover-Nut On Puller Bolt

I make sure the large collar does not obstruct the outer race. Then I tighten the top cover nut while holding the stem of the bolt to pull the outer bearing race out of the steering stem. IT stays in the large collar so I tap it out with a screw driver.

Outer Bearing Race Removed and Inside Large Collar

Outer Bearing Race Removed and Inside Large Collar

I repeat the procedure for the bottom outer bearing race and remove it from the steering head.

Assemble Cycle Works Bearing Tool and Install Steering Stem Outer Races

Some of the parts used to remove the outer bearing races are used to install them with another threaded rod, threaded sleeve and large washer.

Cycle Works Outer Bearing Race Installation Tool Parts

Cycle Works Outer Bearing Race Installation Tool Parts

Outer Bearing Race Installation Tool Threaded Sleeve

Outer Bearing Race Installation Tool Threaded Sleeve

The large washer goes on the bolt, then the threaded sleeve and then the threaded rod.

Outer Bearing Race Installation Tool Parts Orientation

Outer Bearing Race Installation Tool Parts Orientation

Outer Bearing Race Installation Tool Parts Orientation

Outer Bearing Race Installation Tool Parts Orientation

Outer Bearing Race Installation Tool Parts Orientation

Outer Bearing Race Installation Tool Parts Orientation

I remove the new bearing and add the outer race and the old outer race to the installer tool.

Cycle Works Supplied Steering Stem Bearing

Cycle Works Supplied Steering Stem Bearing

New Outer Race (left) and Old Race (Right) Slipped Over Threaded Rod

New Outer Race (left) and Old Race (Right) Slipped Over Threaded Rod

To install the top bearing race, the tool is inserted in the steering stem with the outer bearing race on top of the steering stem and then the top plate with nut is screwed on until the new bearing race is snug and even with the steering head.

Cycle Works Steering Stem Tool Ready to Install New Outer Race Using Older Race (Black)

Cycle Works Steering Stem Tool Ready to Install New Outer Race Using Older Race (Black)

I tighten the nut on the top plate while holding the bolt head on the bottom of the steering stem with a socket wrench. I make sure the new race stays straight with the steering stem and continue to squeeze it into the steering head until the old race just starts to enter the steering head so the top of the new race is snug against the bottom retaining ridge in the steering head.

New Steering Stem Outer Race Installed Flush with Lower Ridge Inside Steering Head

New Steering Stem Outer Race Installed Flush with Lower Ridge Inside Steering Head

I repeat the procedure but orient the installation tool starting from the bottom of the steering head so the cover with the large nut is on the bottom with the new outer bearing race.

Remove Lower Steering Stem Inner Bearing Race

The steering stem is designed with two wide places, one near the top of the stem for the top inner bearing race and another at the bottom of the stem just above the aluminum triple clamp for the lower inner bearing race. I removed the top inner race using a block of wood and a hammer to drive the steering stem out of the inner race. But I use the Cycle Works tool to remove the bottom bearing race from the steering stem.

Steering Stem with Lower Inner Bearing Race on Top of Aluminum Triple Clamp

Steering Stem with Lower Inner Bearing Race on Top of Aluminum Triple Clamp

I use the Cycle Works lower bearing race removal tool to pull the lower inner bearing race off the steering stem.

Cycle Works Steering Stem Lower Bearing Race Puller Tool-Installer

Cycle Works Steering Stem Lower Bearing Race Puller Tool (Top) & Installer Sleeve (Bottom)

The lower bearing puller has a collar with a cut out and a machined edge. The collar fits under the bearing dust shield that fits beneath the bearing and on top of the aluminum triple clamp.

Steering Stem Lower Bearing Puller Collar Detail

Steering Stem Lower Bearing Puller Collar Detail

But in my case, there is no lower dust shield under the bearing. These must be replacement bearings and the person who installed them didn’t install the dust shield.

Installing Steering Stem Lower Bearing Puller Plate Under Inner Bearing Race

Installing Steering Stem Lower Bearing Puller Plate Under Inner Bearing Race

I push the collar all the way under the bearing race.

Steering Stem Lower Bearing Puller Plate Installed Under Inner Bearing Race

Steering Stem Lower Bearing Puller Plate Installed Under Inner Bearing Race

The top of the puller has a bar, two threaded rods with nuts and a center rod with nut and a puller bolt.

Steering Stem Lower Bearing Puller Bolt Parts

Steering Stem Lower Bearing Puller Bolt Parts

Top of Steering Stem Lower Bearing Puller

Top of Steering Stem Lower Bearing Puller

I tighten the bar on top of the steering stem with the nuts on the two threaded rods and with a socket wrench, tighten the puller bolt to pull the bearing race up the steering stem.

Tightening Puller Bolt Lower Steering Stem Bearing Puller

Tightening Puller Bolt Lower Steering Stem Bearing Puller

Once the bearing gets past the wide place on the bottom of the steering stem it will slide up the stem without the puller until it reaches to second wide place where the top bearing race goes.

Puller Moving Lower Steering Stem Bearing Race Up Steering Stem

Puller Moving Lower Steering Stem Bearing Race Up Steering Stem

At that point I reset the bar higher on the two threaded rods and tighten them again and tighten the puller bolt to pull the bearing race past the upper wide place on the stem.

Bearing Puller Adjusted to Pull Lower Bearing Race Over Upper Wide Place

Bearing Puller Adjusted to Pull Lower Bearing Race Over Upper Wide Place

Lower Steering Stem Bearing Race Removed

Lower Steering Stem Bearing Race Removed

Install New Lower Steering Stem Inner Bearing Race

The procedure for the 1977 R100RS is the same as for the 1973 R75/5. You can read about that work here.

The new dust shield on the steering stem goes under the wide part of the inner bearing race all the way down the steering stem.

New Dust Cover for Lower Steering Stem Bearing Race

New Dust Cover for Lower Steering Stem Bearing Race

Lower Steering Stem Bearing and Dust Cover Orientation

Lower Steering Stem Bearing and Dust Cover Orientation

The dust shield easily slides down the steering stem.

Steering Stem New Lower Dust Cover Slides Easily on Steering Stem

Steering Stem New Lower Dust Cover Slides Easily on Steering Stem

I could use the Cycle Works install sleeve and drive the inner bearing race over the upper wide place and snug against the bearing shield. But I prefer to freeze the steering stem and heat the inner bearing race to 200 F and then drop the bearing down the steering stem. It drops all the way down with a nice “Thunk” on top of the dust shield.

Lower Steering Stem Inner Bearing Race and Dust Cover Installed

Lower Steering Stem Inner Bearing Race and Dust Cover Installed

The upper inner bearing race is installed when I install the steering stem into the steering head. I cover that work in a separate write-up.

Rebuild Front Forks

The procedure for the 1977 R100RS is the as for the 1973 R75/6. You can read about that work here.

I use the fork rebuild kit supplied by Tom Cutter at Rubber Chicken Racing Garage.

Tom Cutter's Fork Rebuild Kit

Tom Cutter’s Fork Rebuild Kit

On the left, top are the bumpers that fit into the cap that screws into the bottom of the fork slider.  On the right, top are the rubber boots that fit over the damper rod nuts on the bottom of the fork slider. Below them are the copper sealing washers that fit between the cap and the fork lower to seal them. The blue seals are the fork seals that go in the top of the fork lowers. The aluminum washers below these go in the chrome caps that screw into the top fork tube nuts to seal them.

Back on the left, starting with the second row, are the bumpers that fit on the top of fork sliders. Beneath them are small aluminum washers that fit on the ends of the threaded section of the fork damper rod and beneath them are the larger aluminum washers that go under the nuts that secure the fork damper rod to the bottom of the fork sliders.

Rebuild Fork Slider

I remove the bottom cap by putting the fork lower in the rubber jaws of my vice. I used an old fork tube as a cheater on the handle of the socket ratchet with a 36 mm socket.

Lower Fork Slider with Bottom Cap Removed

Lower Fork Slider with Bottom Cap Removed

The lower bumper fits inside the cap. It’s not uncommon to find this bumper missing as it can dissolve over time. Mine is there, but it’s pretty grungy. I remove the bumper and clean and polish the cap.

Fork Bottom Cap with Bottom Damper (and Gunk) Inside

Fork Bottom Cap with Bottom Damper (and Gunk) Inside

I put the forks sliders in the rubber jaws of my vice, heated the outside around the seal with a heat gun and then I use a seal puller to remove the fork seals being careful to place the hook of the puller into the seal so I don’t put a gouge in the surface the seal fits in. You can see how I did this on the 1983 R100RS here.

The 1977 R100RS fork lowers were painted black. I’m going to have them powder coated so they go into the pile for the powder coater.

When I get the fork slider back from powder coating, I install the new fork seals. Again I put the new fork sliders, wrapped in a soft towel, in the rubber jaws of my vice and I heat the seal area of the fork tube with my heat gun and then use a large socket to drive the seal into the fork tube so it’s square and firmly against the ridge inside the fork slider.

Fork Tube In Rubber Jaws of Vice Ready to Install New Fork Seal

Fork Tube In Rubber Jaws of Vice Ready to Install New Fork Seal

Seal Driven Flush and Even

Seal Driven Flush and Even

The fork rebuild kit includes a new copper crush washer and white bumper that fits inside the lower cap nut.

Fork Slider Bottom Cap Parts

Fork Slider Bottom Cap Parts (L to R) Cap Nut, Copper Crush Washer, Bottom Bumper

I install the new bottom bumper in the fork slider cap nut with the curved end of the bumper at the bottom of the cap nut.

Fork Slider Bumper-Curved End Fits in Bottom of Cap

Fork Slider Bumper-Curved End Fits in Bottom of Cap

Then I insert the new copper gasket under the cap nut, put the fork lower back in the rubber jaws and towel in the vice and tighten it to 60 FT-Lbs.

Fork Slider Bottom Cap with Bumper and Crush Washer

Fork Slider Bottom Cap with Bumper and Crush Washer

Fork Slider Bottom Cap Installed

Fork Slider Bottom Cap Installed

Remove and Rebuild Fork Dampers

The procedure for removing and rebuilding the dampers in the 1977 R100RS is the same as for the 1973 R75/5 and is documented here.

You can use the jaws of needle nose pliers to unscrew the round plates in the fork tube.

Using Needle Nose Pliers to Twist the Round Plate to Remove It

Using Needle Nose Pliers to Twist the Round Plate to Remove It

Or you can use the pins in C-clip pliers you use to remove the c-clip by inserting them into the slots of the plate and twisting the pilers. I used my C-clip pliers and the round plates unscrewed easily.

Use the Pins of The C-clip Pliers Inserted Into the Slots in the Round Plate And Twist

Use the Pins of The C-clip Pliers and Insert Them Into the Slots in the Round Plate And Twist

Here are the damper rod parts I removed. Not shown is the upper bumper.

Damper Rod Parts I Removed (Not Shown is Upper Bumper)

Damper Rod Parts I Removed (Not Shown is Upper Bumper)

I install the new upper white bumper but do not replace the three oil control rings on the top of the damper rod as they are in good condition. I use the BMW oil control ring compressor to install the damper rod and then reassemble the damper rods inside the fork tubes.

Here is a short video showing how I install the damper rods in the fork tubes.

 

Find High Spot on Fork Tubes

NOTE:
This technique comes from Tom Cutter at Rubber Chicken Racing Garage. It’s one of those small details that comes from years of experience and makes a useful difference in performance.

Before I reassemble the damper rods inside the fork tubes (but you can do this afterwards if you wish), I determine the high spot on the tubes and mark it with a sharpie pen. I use a Formica counter top and a flash light. I put the tube on the counter with the flash light behind it. I position my eye so I can look at the gap between the bottom edge of the tube and counter top while I slowly roll the tube in place. At some point, the gap will widen a bit which means the opposite edge of the tube is bent upward a bit. I put a mark on the top ot the tube near the end that mounts in the steering stem. Then when I install the fork tubes I can ensure the slight bow in each tube are in the same plane so stiction is reduced as much as possible.

Checking Fork Tube for High Spot

Checking Fork Tube for High Spot

Fork Tubes with High Side Marked

Fork Tubes with High Side Marked

I’m ready to install the steering stem, new Toaster Tan top brace and front forks. I document that work in a separate write-up you can find here.

2 thoughts on “31 BMW 1977 R100RS Replace Steering Head Bearings, Rebuild Front Forks

  1. did you install the washer, part # 31421232763? i was advised to not use it because it deteriorates and then plugs orifices in the damper mechanism resulting in no damping. thank you for your invaluable tutorials.

    • Hi Colin,

      I didn’t rebuild the spring, ball valve assembly so I didn’t replace that bumper. That said, it’s not the only damper in the forks that deteriorates with time. So, like all things, forks need rebuilding with all the correct parts from time to time.

      Best.
      Brook Reams.

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