Totally worn out rear hub

Discussion in 'Airheads' started by Andy_unaventurous, Jan 17, 2013.

  1. Andy_unaventurous

    Andy_unaventurous Lost but not fearful

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    Greetings knowers of more than me!
    My R80G/S has a totally worn out rear hub, brakes dragging or being ridden on I suspect. Anyway , gotta do something about it for rego. The great guys at BM Ringwood talk of machining out the hub and pressing in a sleeve internal diameter ( when surfaced down) same as a stocky. They are pretty straight guys , but I'm just checking what else is out there? Must have happened to other 31 year old bikes I guess

    Anyone hear about this or have any knowledge of any other way, or indeed (ha ha ha ) have a second hand 3 bolt hub for sale?

    Andy
    #1
  2. 8jest

    8jest Adventurer

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    #2
  3. TEXASYETI

    TEXASYETI Call me "thread killer!"

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    Went through this myself recently. Ended up getting a wheel from Germany and it was not cheap. Someone did a modification where they put a 4-lug monolever reardrive on a G/S. They took a GS paralever rear wheel (4 lug and spoked) and machined some metal off on the inside and popped it on.

    Problem is, paralever rear wheels seem to be just as rare as g/s monolever wheels. I hope that BMW is hearing the increasingly numberous and loud cries for these rear hubs and does something about it.
    #3
  4. Rob Farmer

    Rob Farmer Long timer

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    I didn't think you could sleeve out the GS wheel. the steel drum is cast in below the level of the aluminium around it. Be nice if you could but I don't see how they could fit a new one without chopping out a lot of aluminium.
    #4
  5. Andy_unaventurous

    Andy_unaventurous Lost but not fearful

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    Hi Mate, Impossible to say how many miles, there are some areas where its really tight and you think , wow, low miles, but then I took off the rear wheel and the drum is so worn you have to adjust the brakes up before you can remove the wheel, such is the lip on the drum itself? That there auction is for a diff/final drive, that seems ok on mine
    maybe we'll be able to 3d print one soon :-)
    Andy

    #5
  6. Andy_unaventurous

    Andy_unaventurous Lost but not fearful

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    Hi Rob, please clarify mate, are you saying the 'level' of the brake hub is below the outer cast alloy of the hub? If so is it normal to have to adjust the shoes in to be able to remove the wheel?
    thanks for your thoughts

    Andy

    #6
  7. bikerfish

    bikerfish flyfishandride

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    I always have to adjust the brakes to remove the rear wheel on my airheads, G/S included. before jumping to conclusions, take measurements to see if it is truly worn out, I'm sure someone here has the specs.
    #7
  8. Rob Farmer

    Rob Farmer Long timer

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    Andy,

    I didn't word that too well.

    When the wheels are new there isn't a lip. What I was trying to say is the steel liner is cast into the wheel. I cannot see how you could remove it or fit a replacement in there as the outer diameter of the replacement liner would need to be smaller than the worn original drum to fit it through the gap in the aluminium casting...hope that makes sense...I have a g/s wheel in my spares I'll dig it out and take a picture if needed.
    #8
  9. mendoje

    mendoje Been here awhile

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    Rather than mileage, what is the measured diameter of the drum? I cant recall the number from memory, but the max acceptable diameter is cast on the hub somewhere. As others have said, it's normal to readjust the brakes when R&R'ing the wheel.
    #9
  10. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    I'd be interested in what you find out. I purchased an extra rear wheel from Germany, used and at a pretty good price and was glad to get it. At the time he had one other wheel for sale. I checked and he no longer has it.
    #10
  11. AntonLargiader

    AntonLargiader Long timer

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    The rear hub from my R100R is similarly shot, probably from maladjustment. It is worn with a curve dug into the center of the drum face. I'd love to find a solution for that, also. We have a local machine shop that does some very trick stuff, so maybe I'll ask them one day.

    At least for that bike I can still buy a new hub, but it's not cheap.
    #11
  12. _cy_

    _cy_ Long timer

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    not cheap is an understatement on top of extremely hard to find!

    it's worth noting that original BMW brake shoe material can get extremely hard. either from age and/or very hard to begin with. while it's normal for brake drums to wear a little. most of the wear needs to come from brake shoe materials.

    assuming your drum is still within tolerances... to save what left of your G/S drum. take your drum and old shoes to a local brake/clutch repair shop. find one that will custom fit shoe to drum. if there's wear on drum, thickness for shoes needs to be slightly thicker. reason is max braking occurs at beginning of brake rod travel. when brake cam is in optimal position.

    new shoe material will be much softer than OEM. much rather brake shoe wear vs drum. had no clue just how hard shoe material had become. until I tore into my G/S drum to track down why my rear brakes were so underpowered. getting brake shoes relined with slightly thicker/softer brake shoe lining fixed problems of excessive drum wear and lack of braking power.
    #12
  13. jackd

    jackd Long timer

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    That is a very good suggestion - I'll be following that route when the time comes for my rear wheel to be dealt with.
    #13
  14. Airhead Wrangler

    Airhead Wrangler Long timer

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    For building up spent brake drums I've been curious about trying a thermal spraying process aka "flamespray" or "plasma coating". I've seen various mention of people using this to build up spent wear surfaces before.

    http://en.wikipedia.org/wiki/Thermal_spraying


    These guys even mention using it on clutch plates and brake drums. Some of the coatings can be finish ground after application as well. Looks very promising to me:

    http://www.plasma-group.co.uk/thermally-sprayed-coatings.html

    Hmmmmmm. My only concern would be that the heat might separate the cast-in drum from the outer aluminum casting due to the difference in coefficient of thermal expansion of the two materials. The flame spray process is much lower temp than welding though, so maybe it wouldn't be a problem. Who wants to be the guinea pig?
    #14
  15. supershaft

    supershaft because I can

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    Brake drums are a problem for us. Too bad every airhead ever sold didn't have the brake shoe lining replaced with a lining that actually wears versus the drum! Those linings don't get old and hard. They come brand new like that. The drum wear isn't necessarily from high miles or maladjusted brakes. It's from the linings. A curve dug into the center of the drum? I call that a glaciated drum. The same basic U shape as a glaciated valley. It's from those rock hard stock brake shoes. I see it ALL the time on all the beemers I have been around.
    #15
  16. Beemerguru

    Beemerguru Beemerguru...G/S guy

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    Hi Andy,,,say HI to Chris for me...great guy and took care of my G/S when I stored it at his shop a long time ago. Any chance you've seen a white G/S, Harrison brake, panniers that used to belong to a yank a while back ;-).

    I've got 2 hubs at a shop in the US midwest who will grind the surface smooth and "spray" a metal coating layer by layer to build up the surface back to stock. Then the brake shoes and surface will be cut to fit. Expensive but a lot less than a new wheel or hub.

    The other short term option would be to have the ridge ground down to the current level and have a GOOD brake shop custom fit a softer, thicker brake lining to the shoe to take up the gap. Standard procedure for the bigger brake shops.
    #16
  17. dm635

    dm635 I Roll

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    Reading this helps me realize that my bike must have the low mileage the seller indicated. He says under 12K. He owned from '94 & the title then had 9K. He also says he couldn't have put more than a couple K on it the whole time. The odometer somehow got scrambled & all digits do there own thing riding. I did get the trip odo working correctly so I'll check off every 999 miles on the maint. log I keep. The seller had 3 beemers when I made this one mine. I hardly ever saw him on it in the 8 yrs I've known him. He was either on the 75 or 76 R90/6 or his '85K100RT.

    When I pulled the rear wheel there no ridge on the hub or the drive. No wear there either. I feel I got the best of his 3. The R90 is very clunky I had had no interest in the K bike. The R80 is what was offered to me. Finally having an air head is what brought me here. Now if I can get it ready for spring I'll be a happy boy. Fresh tires, dual brakes & a few pricey items to be safe.
    #17
  18. Airhead Wrangler

    Airhead Wrangler Long timer

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    What shop?
    What material?
    How much?
    #18
  19. peterman

    peterman cop magnet

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    I made a fixture for holding the rear drive in my lathe.
    the one in the pic was sleeved and re-bored to repair the bearing fit.
    [​IMG]

    I have done a few of these.
    [​IMG]
    #19
  20. 8jest

    8jest Adventurer

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    I have local shop that will reline brakes for $10-20 a shoe. Cheaper than a new set.
    #20