33 BMW R75/5 Refinish Rear Shocks

The rear shocks are Boge, and they were the supplier for the original shocks. I believe the shocks were replaced at some point, but I can’t recall when that might have been. Nonetheless, I had to decide if I replace or keep them.

Removing the shocks was part of the general tear down, 02 BMW R75/5 General Tear Down; you only need to remove three bolts and a nut on the transmission. The Boge shocks are not designed for rebuilding. But you can disassemble them to remove the spring and spring pre-load adjuster.

Rear Shock Refinishing Start Point-Dulled and Dirty

Rear Shock Refinishing Start Point-Dulled and Dirty

Shock Disassembly

The first step is to compress the spring enough that the shackle at the top is not being compressed by the spring.  My “poor man’s” spring compressor is hose clamps.  I insert one across three coils at the 12:00 and 6:00 postions as you look down on the shock. Then I insert two more at 3:00 and 9:00 so they go through the bottom coil clamped by the first two clamps and again, to cover a total of three coils.

Hose Clamps for Spring Compressors

Hose Clamps as Spring Compressors

I tighten up the clamps using an 8 mm socket in my portable variable speed drill. I tighten them up going around the circle in increments until they have compressed quite a bit and then use a screw driver to finish up so I don’t break a clamp from over tightening them.  When I’m done, the shackle is now below the top of the shock cover opening up a gap.

Gap Between Shackle and Top Cover

Gap Between Shackle and Top Cover

The damper shaft has slots cut on the side that fit a 10 mm open end wrench. I pull down on the cover so I can slide the wrench in and not scratch the top of the cover. Then I use a screw driver through the shackle to unscrew it from the damper rod.

Removing the Shackle with 10 mm Open Wrench & Screw Driver

Removing the Shackle with 10 mm Open Wrench & Screw Driver

Now I remove the rubber bumper, the bottom spring retainer, pre-load handle and the notched pre-load ring. If you look closely just above the rubber bumper and just below the threads on the damper rod, you see the slots cut to fit a 10 mm open end wrench on the damper rod.

Spring Pre-Load Assembly and Rubber Bumper

Spring Pre-Load Assembly and Rubber Bumper

Here is a picture of the parts with the left as the top and the right as the bottom. Note that the chrome plating on the pre-load adjuster handle and the bottom shock bushing has started to separate from the metal.

Shock Assembly: Left-Top to Right-Bottom

Shock Assembly: Left-Top to Right-Bottom

I tested the shock unit action by putting the shackle back on the damper shaft and pulling the damper fully out and pushing it fully back in again. The action was uniform and steady without any slips. The units push in easier than they pull out which is normal for these shocks.  The seals weren’t leaking, so that’s when I decided to go ahead and refinish the shocks instead of replacing them.

I put all the parts in the parts soaker to get the grunge off them. including the shock units. I cleaned up the chrome on the shock units with “000″ steel wool and then polished them with AutoSol Metal Polish.

I went to work on polishing the shock covers. I started with AutoSol Aluminum Cleaner and “0000″ steel wool to get the oxidation off. I used very fine wool to avoid deep scratches. When I was done, there were several places on the side and on the top with deep scratches. I used 400 grit wet/dry paper to sand out those scratches and then used 600, 1500, 2000 and finally 2500 grit wet/dry paper to leave only very fine scratches.

Next, I use Griot’s polish starting at #2 and finishing with the #4 polish very fine polish using the palm polisher. I applied AutoSol Aluminum Polish and then buffed this with a clean blue paper shop towel. Each shock cover took me about 2 hours to refinish.

Here is the before and after.

Shock Covers: Before & After

Shock Covers: Before & After

And, the final polished covers.

Cleaned & Polished Shock Covers

Cleaned & Polished Shock Covers

The paint on the springs had lost its luster and had some rust spots and missing paint. I tried cleaning and polishing them with Griot’s polish and using some touch up paint, but I couldn’t get them to look very good. So, they went to the power coater, BFN Industries, along with the swing arm.  When I get them back, I’ll put the shocks back together and they will be ready for installation.

Refinished Shocks

Here are the polished parts: shock, spring cover, shackle and pre-load adjustor ring, and the powder coated parts: spring, bottom shock bushing and the adjuster handle.

Polished & Powder Coated Shock Parts

Polished & Powder Coated Shock Parts

I used the hose clamp method to compress the springs, but I wanted to protect the powder coating so I inserted some soft packing material under the clamps.

Hose Clamp Compressor with Padding-Still Got Some Scratches on the Springs

Hose Clamp Compressor with Padding-Still Got Some Scratches on the Springs

However, I did manage to nick the powder coating in a couple of places. But, this time the touch up paint worked very nicely as the gloss of the powder coat and paint match. Next time I use the hose clamps, I will put some rubber tubing over the strap where it contacts the springs.

Here is one of the refinished shocks.

Refinished Boge Shock

Refinished Boge Shock

These will look very nice on the new powder coated frame and swing arm. I’m getting anxious to start assembling the bike.

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