An Unholy Union II: Wp Extreme 50mm Conventionals on a G/S

Discussion in 'Airheads' started by Solo Lobo, Apr 9, 2011.

  1. ontic

    ontic

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    just a quick note before I head to work.
    No news from Roadsacallin yet.

    To anyone with the short threaded blind nut as it came to us new- I highly recommend trying either an older long threaded one, or making yourself a steel one like I did (very easily) out of a olde swing arm pivot thing.
    One day in the future I'll probably be sending something to Solo (you still want that airbox?) so I could easily include a heap of these steel blind nuts (I have three more on hand I could make and can cheaply or freely get more from my parts guy).
    With more thread in that stem and particularly with the steel blind nut, you really can torque it up properly.
    Secondly I'd say if you are redoing the stem torque on the centerstand with the front end hanging, do it the way I theorised, cause it works well. Loosen the top triple stem pinch bolts only- then loosen the lower triple fork pinch bolts- then the top triple is supporting the weight of the front end and you torque the blind nut which is only pulling the lower triple up and loading the bearings.
    I agree with Jenna that this stem and system is not ideal, but I agree with Solo that if you torque it up and preload the bearings correctly, then clamp down all the pinch bolts, it shouldn't be going anywhere.
    Saying this, Jenna seems to be the only one who has heavily tested it. I certainly haven't.
    I had numerous things going on with mine, but after sanding and polishing steps out of my stem (upper and lower bearings had nocked ridges in the stem) which has by the way reduced my 'interference fit', and using a long thread steel blind nut, I can get a very smooth linear increase in bearing preload as I torque up the stem- I couldn't get this before. I can now very easily way over-torque the head bearings without it feeling like I am about to strip the stem thread. I couldn't do this before.


    cheers,
    Gotta run.
  2. Solo Lobo

    Solo Lobo airhead or nothing

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    yes, please!:D I believe I have the longer bolt on there now but steel sounds better.

    BTW, I just sent an email to a former local BMW rider who was the/a sales manager at Scuderia a while back, asking if he could reach out to whoever he thought was the most knowledgeable tech for these older fork and see if we can get a definitive set of instructions on pre-loading from someone who know best.
  3. Airhead Wrangler

    Airhead Wrangler Adios Mexico

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    The problem is that the optimal preload depends on what bearings you're using and more specifically the contact angles on the races and the taper of the rollers. What worked on KTM bearings is not ideal for bmw bearings. What would work best is to take the torque spec for the original GS stem, figure out what from thread diameter and pitch what compressive load that torque exerted on the races and then figure out how much torque it would take to achieve that same load with the bolt that we're now using.
  4. Solo Lobo

    Solo Lobo airhead or nothing

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    Gottcha, what I hope to get is the definitive way KTM tech's pre-loaded these bearings. I understand this may not work for our BMW's, but it is valuable info right?


    Here is the BMW spec - the torque for the slotted nut is specified as "tightened without play"

    [​IMG]
  5. hardwaregrrl

    hardwaregrrl ignore list

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  6. Solo Lobo

    Solo Lobo airhead or nothing

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  7. Beater

    Beater The Bavarian Butcher

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    Ahhh ... just the tube. Got it. Thanks.

    :lurk
  8. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    Jenna, if you decide you want to try the threaded swing arm pivot thingy let me know and I'll look to see if I still have it.
  9. hardwaregrrl

    hardwaregrrl ignore list

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    Sorry, just rubbing it in!:D

    Guess we should have had some more R&D reasearch done before we had Guy poop them out. It's a bummer Rdubb never chimmed back in with one of his projects. And Marcus if you're out there.....let us know whats up with your head bearings. I'm certain I've not encountered anything near a Siberian road.:ear
  10. Solo Lobo

    Solo Lobo airhead or nothing

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    There are at least a handful of folks from the first run who have been riding... too bad none have chimed in here.

    I may go back to the original thread and see if I can get any to come on over.

    Since this design worked for KTM's of every size and shape (including PD racers and 950's) I am still hopefull it will work out fine, my triples have no slop right now.

    I am worried about the main wiring harness routing between the fender and lower triple... need to find a better way to route it.
  11. hardwaregrrl

    hardwaregrrl ignore list

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    Yeah, I hated that design as well and re-routed it between the triples.
  12. hardwaregrrl

    hardwaregrrl ignore list

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    Here's what I'm doing with the bike.

    <iframe width="560" height="315" src="http://www.youtube.com/embed/pUgTWTUXfao" frameborder="0" allowfullscreen></iframe>

    Sorry about the quality.
  13. Stagehand

    Stagehand Imperfectionist

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    Great video!@ I would LOVE to ride that road :clap
  14. hardwaregrrl

    hardwaregrrl ignore list

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    Thanks....never had a gopro. Not sure how to get better quality without taking 2 hours to download. Come on down and ride with us!!!!!
  15. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    YEAH, what she said, LBL 200 mountain bike single track open to bikes!!!

    I'll find out if it's wide BMW friendly. I plan on taking the DRZ this year.
  16. Stagehand

    Stagehand Imperfectionist

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    well yeah thats a quandary. Have to go somewhere that has a big upload pipe. I am lucky enough to have a T1 line at work.. make's CHILDS PLAY of even HD stuff. MEanwhile i dont seem to even be able to upload pics to smugmug from the DSL at my house. Its easier to send stuff over AT+T's 3G network than the stupid phone lines.
    Thats not saying much :huh

    Old friend of mine form Atlanta is getting married in early june... Wish I could make it down for that@ but I'll just have to push it into the hot season
  17. ontic

    ontic

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    Before I forget,
    Jenna, you are using both the upper and lower bmw dust seals above and below the bearings aren't you? Even if you are you might want to check if the top of your stem is making contact with the bottom of the washer on the blind nut as you torque it up. A bit of squashed soldering wire in there proved it for me. As I said, buried in a long post a while ago, without the shimming of those very thin dust seals the top of my stem was hitting the blind nut washer- after a point I was just torquing up the stem and not adding preload to the bearings- and no doubt this was the reason I originally stuffed up- there was no noticable play in the steering during this, I torqued the blind nut, it all felt good, but it wasn't, and I somehow rattled some ridges in my stem.
    The tolerance is very tight- maybe 1-2mm max by my reckoning (on my bike). Has BMW varied the length of their steering heads at all?



    Cool, no probs, the steel does feel a hell of a lot better when torquing up, and by using the nut that comes on that swing arm pivot thing it gives the exact same bolt/nut head size as the short threaded blind nut (which also fits one of my stock bmw toolkit tools). If you also have the older aluminium long threaded nut, then you probably also have the separate alu washer that came with it and you can use that on the new steel blind nut.
    I'll make a couple more up from what I've got at hand. If anyone else wants one, just let me know, otherwise it is not hard at all to make if anyone has a welder at hand and wants to try (just ask if 'instructions' are wanted).


    Where were you a few pages back when I was pontificating at great and tiresome length about different bearings and contact angles:lol3
    About the bmw torque spec- do they ever give one? That is the problem with the crown nuts, very hard to give a proper torque figure that we can use, and at least on the older stems the preload that crown nut torque exerts then changes a tad once the top nut is torqued down.
    This is why I am trying to focus on setting the preload by the fall-away point and the general feel at the bars. If we can get that right, then we can hopefully agree on what blind nut torque got us there.

    Unfortunately I do not think that the short threaded aluminium blind nut will safely get there.
  18. hardwaregrrl

    hardwaregrrl ignore list

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    Here's another...

    <iframe width="560" height="315" src="http://www.youtube.com/embed/0calsc23TJo" frameborder="0" allowfullscreen></iframe>
  19. hardwaregrrl

    hardwaregrrl ignore list

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    I understood where you were coming from with this. Having the lack of big words, I couldn't defend your theory. But it makes perfect sense that the steeper the angle of the bearing, the more load you'll have to put on it to seat it in the race!
  20. ontic

    ontic

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    This is the contact point your looking for- the gap between the thread on the blind nut and the OD of the stem
    I coiled up a bit of very thin soldering wire into a perfect circle the right size (after stuffing up the first time coiling it roughly around my finger and screwing it into my stem thread:D)

    [​IMG]

    And no probs, one more steel blind nut coming up. I wonder if I should look into getting these things chromed so they don't rust up...?