Rear replacement shock /5 (not a Koni/Ikon discussion)

[StephenB]

1972 R75/5

My rear BMW shocks are from Boge, P/N 1-0201-22-759-0. They also carry the BMW OEM P/N 1 230 274. Does anybody have a source for the hydraulic unit that you recently used? I really don't want to buy NOS when it comes to shocks.

Also, from another (seemingly aftermarket) set I have: p/n SW 581 on the shocks. It had two piece springs installed: longer black/shorter blue.

I measured/calculated the springrates of both stock and the 2-piece using an online spring rate calculator:

Spring 1 (two parts): blue spring -> 2.3in 86.5kg/mm, black spring -> 7.5in 23kg/mm
Spring 2 (one part, 2 sections): section1 -> 3.95in 56kg/mm, section2 -> 6.25in 28kg/min

I don't take those numbers as correct absolute values, but compared to each other are valid. Spring 2 appears to be softer from initial deflection. Both however are not progressive, just have plainly 2 springrates.

Were the original stock springs progessively wound on both ends? I have what I believe to be stock springs and both ends are tighter wound (but not progressively), hence have a different spring rate than the center section, in a 1/3 to 2/3 ratio.

I will probably start with the 2-spring solution and if a replacement hydraulic unit can't be found I will have the original Boge rebuilt (not a standard rebuilt, it involves some machining).

Any opinions, experience out there?

[Motorhead]

I know I will be roasted for this

But the Stock shock for a Sportster maybe crap on a Sportster but they will dampen and work nicely on a BMW 246 and 247 dual shock fit

they come in 13.0 and 13.5 ALSO Shorter but the 13.0 I used and sold to others love them

[Garnet]

Stemler changes up the /5 Boge damper 33 53 1 230 274 to 33 53 1 231 498 which they sell for 125E each. Not sure if these are the correct length for a /5.

Ulis lists Boge dampers for 1970 - 84 for 120E each. I asume they are the long (340mm?) ones for the later bikes.

SWB /5s should use the correct length shock (can't remeber the length off the top of my head) as the later taller shocks will reduce the rake and make the "turn in" even quicker than it already is. I have treid this and found it fun in the city and on the tight backroads where I live, but I'm not sure how long I would be happy with that on a long highway trip.

I tried Betor shocks from Motobins but found the compresion damping too stiff for a nice ride quality.

The other problem I have seen with the popular replacment shocks (Ikon and Hagon) is that they only have around 3" of travel compared with the almost 5" of the Boge originals.

Stephen, I'd be intersted in haveing my original Boges rebuilt if you think it can be practicly done.

[Major Softie]

That SW 581 shock is an S&W shock (yes, aftermarket). They were a very popular replacement shock in the 70's and maybe early 80's. The company is somehow affiliated with Progressive Suspension: It morphed into Progressive, or Progressive bought them out, or something. Last I knew, Progressive still even sold replacement springs for the old S&W shocks.

[StephenB]

have emailed S&W and will see if your know your stuff MS

[Major Softie]

I'll be interested to see if they still have springs for those. I think it was at least 5 years ago that I remember them still having them, maybe longer.

[StephenB]

Here's what Progressive had to say:

It has been many years since we’ve worked with S&W shocks. Unfortunately we no longer have any specs or technical information on the older shocks.

[Motorhead]

Hey I might sell FReds works 14" shocks nice fit and good ride no leaks or problems I'll clean them up for a sale

[mattcfish]

have emailed S&W and will see if your know your stuff MS

Don't know if it matters. I've got an old set of S&W springs in my parts heap. Yellow springs with black (rusted) shocks.

[StephenB]

The Boge and the S&W springs have different dimensions, but I can marry S&W springs with the Boge hydraulic units. Matt, if you want to get rid of those springs I'd have more options and can try various combinations. Send me a PM if you like.

Stephen