1972 R75/5 rear hub

Discussion in 'Airheads' started by lancruza, Apr 18, 2012.

  1. lancruza

    lancruza On a Mission

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    I've been working on the restoration of my 1972 R/75. Tonight I was putting the left side bearing back in after it had been cleaned and greased. I ended up with a gap next to the oil seal. I don't remember there being a gap like this when I removed the back wheel. I've pulled the bearing back out and put it back in several times. Everything seems to be lined up correctly. Any insight on where I might have gone wrong would be appreciated.



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  2. Boxer Metal

    Boxer Metal Mad Scientist

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    Pull the seal retainer back off and turn the spacer around so only the thin part of the spacer is sticking out and the hat/flanged part is riding against the bearing. This way when you remove the axle the spacer stays in place.\ and only a few millimeters is sticking out.
    #2
  3. lancruza

    lancruza On a Mission

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    I've tried turning it around and putting the flange behind the oil seal so it is up against the bearing. When I turn it around and the flange is against the bearing it pushes the oil seal out far enough that it will not seat properly in the collar. There is nothing to hold the seal in place.
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  4. pommie john

    pommie john Long timer

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    bmweuro is right, it goes in the other way around, flange inside the seal.
    Just from memory, that seal looks deeper than I remember. Is that a new seal? My vague memory says it should only be about 5mm deep ( that's a vague memory so I might be wrong).
    #4
  5. pommie john

    pommie john Long timer

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    Just checked, the oil seal on mine measures 5mm deep. Is yours deeper than that? It looks it in the photo.
    #5
  6. lancruza

    lancruza On a Mission

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    Thanks bmweuro. One diagram I have shows it goes flange out and I have another that shows flange in, so i wasn't sure which one was right. Yes, you are right pommie john, good eye on the seal, the previous owner must have put in the wrong seal. I just measured mine at 8.6 mm. I went and checked Hucky's parts online and he also shows the inner seal to be a 5mm. That is probably why this seal seats in the collar loosely. It actually will spin in the collar. Am I right that with the correct seal in place it should fit firm into the collar?
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  7. erimille

    erimille Adventurer

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    Having recently done a similar process to my 1972 R75/5, i found the following thread (and included picture for convenience) useful in reassembly.

    - http://www.advrider.com/forums/showthread.php?t=388220

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    *note* this is the front, not rear wheel, but hopes this helps,

    --e
    #7
  8. lancruza

    lancruza On a Mission

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    Thanks for the great picture and the thread link. Now I'm confused again --<:kboom>-- This shows the flange or the tophat going to the outside. Well let's go read and study some more. When you redid your hub, did you have any kind of gap between the tophat and seal??
    #8
  9. Wirespokes

    Wirespokes Beemerholics Anonymous

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    Once you get the correct seal that fits tight, don't worry about the thrust spacer (top hat) and which direction it goes. It will work either way.

    With the flange on the outside the seal is possibly protected, but if the wheel is removed to fix a flat beside the road, it's possible for it to fall out and get lost. That's why most of us run with the flange on the inside - it can't possibly fall out and get lost!
    #9
  10. pommie john

    pommie john Long timer

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    I'm not surprised you're confused .. the photo is WRONG!!

    The flange should be inside the seal .
    #10
  11. disston

    disston ShadeTreeExpert

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    The top hat spacer will fit the wheel either way. It is the length of the spacer that is showing something is not right. With the hat brim out side the brim should be closer to the seal. Possible the seal is not the correct item but it can be the wrong wedding band spacer, or is something, like a stone, or something, stuck it the wedding band area. When on the bike does the wheel have an excessive amount of wobble. Too thick a wedding band will cause wobble.

    I had a hard time with the spacers and seals recently on my /6. I think these are different but what I found was some of the spacers were not in the right place. The /6 rear wheel has different length, depth, spacers, left to right.
    #11
  12. lancruza

    lancruza On a Mission

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    I don't know if it has wobble. I rescued this bike out of a field and have not ridden it yet. I am currently going thru and fixing things as I get to them. Everything is seated properly as far as I can tell. Maybe the wedding ring spacer is the wrong size. I guess once I get it rideable I can adjust from there. I did notice that there is also a gap on the front wheel, but it's not as large a gap as the rear.
    #12
  13. disston

    disston ShadeTreeExpert

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    A bike with a history like that may have the wrong parts or parts in the wrong order and weird stuff. Good Luck.

    Are you familiar with Duane Ausherman's site? He talks mostly about /2 and /5 set ups but over all there is more of an understanding of what you are looking at.

    http://w6rec.com/duane/bmw/
    #13
  14. GeezWhiz

    GeezWhiz Been here awhile

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    I have the rear hub of my '71 R75/5 sitting on my bench and I just checked it against your photos. My bike has only 21K on the clock and and was last tagged in 1979 and I'm fairly confident that it has not had the hubs disassembled before. For what it's worth, my hub looks just like your first try. The "top hat" is to the outside and there is a gap just like your photo shows. It fits flush to the inside of the hub cap. I can post photos tomorrow if you want.
    #14
  15. ericrat

    ericrat Long timer

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    Overall it is a pretty good design taking into consideration bearing and manufacturing tolerances, wear, etc. But damn there are a lot of parts to keep straight in there.:rofl
    #15
  16. lancruza

    lancruza On a Mission

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    Thanks disston, lots of great info at Duane Ausherman's site. Very good detail.
    #16
  17. lancruza

    lancruza On a Mission

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    Thanks GeezWhiz, From the looks of these hubs, I don't think they have been apart either. It's good to know that someone else is seeing the same thing. After reading about the bearings over at Duane Ausherman's site, I'm thinking it's probably spaced like this for preload purposes. It just looked weird to me to see the tophat with a gap like that between it and the seal. I hope to do the "shake the wheel" test as described on Duane Ausherman's site within the next couple of days. Thanks again.
    #17