R50S silent block question

[jwonder]

Okay historians,

I have an R50S I am restoring and the left rear silent block pictured below is M10, not M12. The book says it should be M12. It looks correct and most everything on the bike has been correct but it’s not the right size as per the parts book.

I can certainly bore it out and put the larger silent block in as there is enough space but I wanted to check with the group first because I know there was some strange stuff on the R50S. I have been told many times there were strange bolts on the R50S and figure maybe this is one of them.

Any help and guidance is greatly appreciated.

[wa1nca]

Salis site list all r50-r69s and r50s silent blocks same part # and 12mm center and mounting bolt also 12 mm
https://bmwclassicmotorcycles.com/index ... orber.html
10mm would seem too small
Tommy

[schrader7032]

Part number 33533054296? Called "rubber mounting" on RealOEM...no sizes shown. Indicates that it was used on all /2s from 1955-1969. At least the part number suggests that...not sure what the actually installed parts ended up being. Per Bench Mark Work, they call it "shock silent block bushing twins rear" suggesting for all /2 twins. Call to Vech tomorrow??

[Daves79x]

Any chance the 12mm one would just press into the existing hole?

Dave

[jwonder]

Measured the hole, it’s about 2mm too small. I can ream it out no problem for the larger one but wanted to know before I did that.

[wa1nca]

Any chance the 12mm one would just press into the existing hole?

Dave

Wow I didnt know this
the front silent bushing is smaller and uses a 10 mm bolt
https://bmwclassicmotorcycles.com/index ... nsion.html

The rear silent bushing is larger and uses a 12mm bolt
https://bmwclassicmotorcycles.com/index ... orber.html

If the mounting bolt for the rear shock on the r50s is a 10mm bolt then I would order the one for the front that uses a 10mm mounting bolt

As Dave says if the outer diameter is the same on both then the r50s indeed is different from r50-r69s and uses the smaller 10mm one both front and rear
Tommy

[jwonder]

Tommy,

I am not sure yet. I received this motorcycle partially in boxes and you never know if the bottom got switched up with a R27 one by accident.

Anything is possible but with everything else being as right as I have seen for a motorcycle not fully together it does make me question it. If there were tons of parts not right I would question it more. So it’s possible this is the one thing I find that is not the right part or……

[wa1nca]

rear 10mm would be for r27-r26
too bad you couldnt just change to a 12mm silent bushing but the r50 r27 silent bushings are not same also springs and shocks are also different
Tommy

[schrader7032]

I guess I'm not following totally. Is an R26/27 shock exactly the same except for diameter of the eye? Is it thought that this "imposter" shock a front R26/27 now being used on the rear? But don't rear shocks have the built-in handle to change spring rate?

[wa1nca]

Difference between r27,r26 and r50-r69s rear shocks
#8 shock
#9 spring
#12 telescopic eye
#13,#14 silent block
r27 r26
https://www.bmwclassicmotorcycles.com/p ... bsorber-2/
r50-r69s
https://www.bmwclassicmotorcycles.com/p ... pension-2/
Tommy