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
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 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
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
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
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
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
And, the final polished 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
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
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
These will look very nice on the new powder coated frame and swing arm. I’m getting anxious to start assembling the bike.
Hello Brook,
I have an identical pair of BOGE’s on my ’76 R75/6. The shocks work fine, and I cleaned them up, BUT, I need a new set of bushings for both shocks. The metal spacers are fine but some of the rubber material has collapsed or degraded significantly.
Having trouble finding these parts: Any advice…?
And as always, thank you for your help!
Luis
Hi Luis,
I don’t have a source for these. But, I suggest posting this question to the micapeak airhead group as I suspect others have found a source for these.
[email protected]
To Subscribe: ttp://micapeak.com/mailman/listinfo/airheads
Best.
Brook.
Hello
I rebuilt my rear shock (1974 R75/6). Hams at Hucky’s said he could order the bushings, but I found my local BMW dealer could order them. The upper ones were 5.98 each and arrived in two days. The original parts # did not work, but he found them on his parts diagram. Now to press them in??
Good luck
Jim
Hi James,
Thanks for dropping by.
Interesting. IIRC, the original Boge shocks are not rebuildable (seals, oil, etc.). The bushings that the mounting bolts go through do wear out after awhile, so good to know Hans @ Hucky’s can source these as well as the BMW dealers.
Best
Brook
Thanks for easy to understand dialogue and pics for beginners in my 1974 R90S fun rebuild…..
Hi again Brook! I did exactly as you showed in your description and photos, but found the lower bushing and adjuster rings would not clear the top of the cartridge. How did avoid damage to the cartridge when removing them for full disassembly? (I have the leaky one apart, and have sourced another cartridge).
Hi Ken,
I did not have a problem sliding the bottom spring bushing and the the preload adjustment handle off the body of the shock. It could be the top of the shock has mushroomed for some reason. IF, these are Boge shocks, then the ring should slide off. The Boge are not rebuildable. IF these are Koni shocks, I believe they can be rebuilt. But, I don’t know if the Koni use the stock BMW preload adjuster and lower shock bushing.
Best.
Brook.
Thanks Brook. It looks to me that you may have had a different Boge shock. Both of mine have a cap, giving the top of the cartridge a kind of collar, something like plumbers put on the end of a pipe to block flow. To me they are obviously the way they were designed. I will talk to my local shop about them. I’m assuming the left and right face opposite re. the preload lever, so I have to get lucky the one he has being the left! If so I believe I can blast and paint the springs, and polish up the cartridges so everything looks good. If not I’ll be looking for a left Bogey shock.
Or, you could get a good modern shock. The Boge was not all that great a shock. Something to think about.
Best.
Brook.
Thank you Brook! I was considering restoring and storing a set for show or resale purposes So they don’t wear (I sourced a new set of aftermarket cheap on EBay). I hope to ride the R75/5 toaster for several years once it is finished, and sell a couple of other bikes to have the $ for my penultimate project: a 1955 R50. I have to slow down a bit, having just turned 70!
I meant when I eventually sell the bike they’ll be mounted..
Hi Brook
Great site. You referred by Bob’s BMW. I am the original owner of a 1973 1/2 R75/5 long (now with 220,000 miles), I bought it new April 18th 1974. Forty years later I bought my current bike a R1200RT wethead for daily riding. So, I’ve begun taking apart the fairing, bags luggage rack oil cooler and am bringing it back to stock. I had /6 shocks/springs on the bike but now am putting new /5 shocks with covers back on the bike. I used your method of spring compressing to get the old but good /6 springs off and reinstalled them with the new shocks and covers. Now, I have the bushings to install on the top of the shock retainer. Do I need a hydraulic press to press them in? Should I file them down slightly so they slide in?
Thanks,
Jeff
Hi Jeff,
I have not replaced them. But, I think you can use a suitable size socket to help drive them in. Or, you can use a long bolt with washers on either face of the bushing and then tighten a nut to press it in.
I hope that helps.
Best.
Brook.
Brook,
Socket and a vice works, dam they were tight, but I managed to press them in without wrecking anything.Have them all put together, they look great, now I’m cleaning up the parts near the shock mounts before I put them back in.
Thanks for your comments,
Jeff
Hi Jeff,
Cool beans. Best of success on your project.
Best.
Brook.
It is now 2020 and I am doing the bushing replacement on my shocks. any words of wisdom when pressing them back into the shocks? how to keep them aligned? use any heat? They are really tight as you mention. been a long while since your posting – but giving it a try anyway for advice.
Mike Z
Hi Mike,
I suggest using some washers and a bolt to press the bushing into the hole in the shock. Put a washer on either side of the bush and then put the bolt through it and the eye of the shock. Tighten up the nut and it should force the bushing into the eye of the shock. You could try freezing the bushing before hand and use a little 3-in-One oil on the inside of the shock hole to ease the bushing into the hole.
I hope that helps.
Best.
Brook.
patience was part of the key, along with several attempts, finding some spare bolts and lengths of metal tubes to accomadate the threaded area on the bolts. I got it in 🙂 one side done
Good to hear Mike. Onward through the fog 🙂
Hi Brook!
I struggled with R75/5 rear shocks also. Following your house clamps method I got mine apart. My local shop (Shail’s Motorcycles) pronounced the cartridges worn out. I took a chance and bought shock cartridges on Ebay for $50. figuring on the size being right, devised my own shock compressor, but found the stock bmw aluminum collars too small, which kept the tops from centering. A local machine shop reassembled them for me, widening the opening. All good now! Live and learn!
Hi Ken,
” Live and learn!”
Some days I learn a life-times worth of stuff in just a few hours, and I usually have the bloody knuckle or finger to show for it 🙂 I’m glad it worked out for you.
Best.
Brook.