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

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

  1. redboots

    redboots Johnny Lung

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    Don't like it.
    Been reading my BMW manuals and for the early type like that now fitted to my bike, it describes the procedure of removing all free play. No more. The top nut is then torqued down to large figure to hold it all together. Not to exert a load.
    The later models have a different adjuster that carries the top bearing. This is just a large "saucer" with a knurled edge so you can adjust it by hand.

    I think the idea of the different types being able to accept more or less "preload" is not valid and refers to the loads exerted after fitting (correctly:lol3).

    I have just been for a ride on mine and they were a little on the tight side... it felt like there was a steering damper on there... remember the old screw down ones people used to fit to Triumphs... (Nortons never needed them:D)
    Its a little better after 100 miles but I think I will back it off a CH. Try the KTM way. Get a helper to slowly turn the blind nut while you hold the forks and rock them fore and aft to feel for movement. Stop when there is none and lock it all off.

    Writing that may have just put the light on!
    The blind nut. IS IT THE RIGHT ONE? There should not be a washer used.
    Looking at rdubs(?) drawing of the top clamp, its the same as the KTM system. The pinch-bolt not only pinches to the stem, but also the blind nut. This is what locks it all together... Not torque... or am I talking bollox:wink:


    Cheers,
    John
  2. redboots

    redboots Johnny Lung

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    First road test and I like it:clap
    I put a wire-tie on the stanchion before riding it and after a few ham fisted applications of the brake, I managed to push it up by 153mm, leaving me 54mm "spare". I may drop the forks down a bit more as that seems a lot [​IMG]

    [​IMG]

    The bike tracks really well and soaks up rough roads a treat.
    I have some problems with the lack of steering lock. I will have to grind some of the cockpit away to clear the top of the legs unless I can slide enough through the top triple.

    Looks good as well... impo:wink:

    [​IMG]

    [​IMG]

    Also need to lengthen the side stand a bit and I think I may have a front wheel bearing on the way out...


    Cheers,
    John
  3. hardwaregrrl

    hardwaregrrl ignore list

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    Looks nice, John!!!:clap:clap:clap What will you do for gaiters??
  4. redboots

    redboots Johnny Lung

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    Thanks very much:beer I wanted to keep it looking a bit like it should. Thats why I didn't go for USD forks.

    Thinking about something like these: http://www.dirtskins.com/
    I have one on the rear shock and they make them to the sizes you want.

    Cheers,
    John
  5. ontic

    ontic

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    Looking great John, congrats:clap
    Looks like a lovely spring day too- it was raining and cold and miserable today (and most days) here.

    now back to the bearing stuff,

    Technically the top nut does actually exert a small load, because when you torque it up properly it pushes the crown nut down to the other side of the threads- that is one of the reasons the adjustment on that older style bmw stem (like on my R90) is a bit fiddly- if you set it 'right' with the crown nut, then torque up the top nut, it gets too tight. The later (GS etc) style system set about 'fixing' this issue. I think Antons site goes into this, but that is beside the point.
    I also believe that technically there is meant to be some preload, wether or not the bmw manuals decide to call it that. Not a great deal but a little bit- it does go beyond removing free play- and comes down to setting the 'fall away' (the point where the bars will fall once turned)- the fall away point is determined by the drag on the bearings and the drag is produced by preload... and for me, what is important here is that the steeper the contact angle of the bearing, the more torque will be required to remove play and get to the correct preload that will give you this correct fall away.
    That was a mouthful.

    My argument (based for the moment on limited understanding and gut feeling:D) is that in order to fit tapered roller bearings into steering heads 'properly' they need to be preloaded correctly and that the steeper the contact angle on the bearing, the more torque and/or preload is required.
    Try to think about it in terms of an extremely steep angle vs an extremely small angle tapered roller bearing.

    [​IMG][​IMG]

    I know how to set the right preload on an airhead (my R90)- that is I have had the experience of both too loose and too tight bearings and I now have a way (eliminating play, testing the drag on the bars and setting the fall away point, and of course feeling how the bike rides after all this) of setting this preload in the middle- which to me is right. There is no way that I could get the torque required on the crown nut by twisting it by hand- it taks a good deal of leverage on the crown nut with the special tool to get to this point.
    What I find it very hard to do is to reach this same point on my G/S with these same bearings but a different stem and tightneing method. I can get there, but like I said, it comes from torquing up that blind nut to 35-40 ft'lb, not 7.4 ft-lb, not even close.



    see, that is just my point:D It is virtually impossible for me to (currently) get to that too tight point that you just easily and accidently got too.
    For me, I think hitting 40ft-lb on that aluminium nut just started to feel like it was heading into the too tight zone, and this was well and trully into the torque zone that felt too tight for the aluminium blind nut (not the bearings:D)



    Call me dubious but I've already sanded one step out of my stem from (I can only assume) the steering head having too much play and hitting speed bumps for a couple of hours hammering them back and forward. Considering we are using bmw bearings in the steering head, I am more inclined to use the tried and tested method of removing play, and setting the (very slight) drag and the 'correct' fall away point of the bars. The KTM instructions don't get me there.

    here are two blind nuts- the one of the left is the new ones that have a washer built in- the thread, the washer and the nut head are all one piece of metal. Good observations! You might be right in that the triple might pinch the washer as well as the stem- at 7.4 ft-lb of torque on the nut I suppose that is a good thing as loosening out might be possible?
    The other one with more thread is an older one from my ktm triples that came with the forks, it has a seperate washer which won't do a thing if pinched, however it has more thread and felt much better being torqued up to 40 ft-lb than the other one did...

    [​IMG]

    I don't know, this might all be a storm in a teacup. If my idea of different contact angle bearings needing different torque to reach no play and the right preload (for steering head application) is correct, hopefully we have enough redundency built into the ktm stem/nut system to get to where we need to be on the bmw bearings (without stripping the stem/blind nut threads in the process).

    What I can only repeat is that 7.4ft-lb torque on the blind nut, no matter how much you pound the triple clamps and shake the forks, TO ME (and I might be doing something wrong), does not feel anywhere near enough preload on the bearings, and it gives a fall away point that is pretty much a fraction of a degree off from center (ie, falling too soon in my experience).


    Sorry for the long tedious posts peoples. Hopefully it is of some interest or use, even if it is just for an engineer type to step in and completely discredit everything I am thinking. I'd like to get this right,

    Cheers,
  6. redboots

    redboots Johnny Lung

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    Its ok. Sometimes just writing it down will clarify things... or not:freaky

    John
  7. hardwaregrrl

    hardwaregrrl ignore list

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    So....$120 bucks later!!!!! My stem was too large for the inner race to slide down. It took him quite a while to remove the lower bearing race. Stem and bottom clamp are in the freezer and bearings are greased and under a low watt bulb. I should be back on the road in a few hours!!! Well, maybe by 9pm est.
  8. ontic

    ontic

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    Ouch. What, does he turn them down with gold chisels and polish them with diamond powder, that he grinds up himself, from big diamonds?:D

    I'm baffled how you got your bearings on in the first place!
    Good luck this time, I hope it goes well.
    Maybe we could talk about fall away angles- mine (preloaded at 35-40ft/lb) falls at a very slight turn of the bars- like the very front of the tyre moving 5cm or less to one side (which is very little at the bars).
    Off to work, hoping for good news when I get back,
  9. hardwaregrrl

    hardwaregrrl ignore list

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    Yeah, I think I wanna be a machinist when I grow up!:evil:evil He also repaired the threads in the stem and on my 2 blind nuts, and he removed the inner race of the bottom bearing off the stem. Have a good day at work!
  10. hardwaregrrl

    hardwaregrrl ignore list

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    Hey, what are you guys using for torque value on the pinch in the lower, upper clamp and at the stem.??
  11. Solo Lobo

    Solo Lobo airhead or nothing

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    As a talented sprint car mechanic I know well once advised me:

    "make 'em tight enough they don't get loose, but don't make 'em too tight because you might just strip those F*$@*rs"
  12. Solo Lobo

    Solo Lobo airhead or nothing

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    So it's been more that two weeks since I rode my bike, and when I went to remove the bleed screws I got a nice "hiss" from both side..

    A bit of trick bits ala ontic:

    [​IMG]





    [​IMG]

    [​IMG]
  13. redboots

    redboots Johnny Lung

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    Whatever you decide, KTM say to locktite the stem pinch bolts... not the leg bolts though.

    Cheers,
    John
  14. hardwaregrrl

    hardwaregrrl ignore list

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    Thanks John, also recommended to loctite the blind nut. SOLO had a lookie see about torque values on the leg pinch bolts. Looking at all sorts of manuals last nite, one thing stuck out...the upper pinch bolts have a higher value than lower. I don't know why, but that was a very common theme. I went 15 ftlb on the lower clamp, stem pinch, and blind nut. And 20 ft/lb on the upper pinch bolts. I did back off of the blind nut a bit before I went to town on the stem pinch.


    Legs are a little lower in the top clamp compared to last time, i'm going to try and come home a bit early and hit my local whoops to seat the bearing, but I have to go to work tonight on the bike, a 90 mile round trip on the hwy. Funny thing is even with that bearing completly toast last saturday, I never ONCE felt it on the road!!
  15. ontic

    ontic

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    Bump:ear

    I'm laid out with a heavy cold this weekend. Can barely get myself off the couch let alone out to the cold windy shed.

    Gimme some news!:D

    Rather than continue to clog up this thread with my theorizing about different bearings and preloads and torques, after chatting with Marcus (roadsacallin) about his upcoming Scotts damper install, I asked him about his experience with these steering head bearings and these clamps/stem/blind nut.

    He is going to check in here and enter the discussion sometime after his his current ride, suffice to say my paraphrasing is: he did have problems resulting in replacing notched bearings (around 18,000 Miles and 30,000 Miles), and he believed this was because they were not tightened enough, and he recalls feeling like the top nut (same newer 'short thread' nut that we have) didn't seem like it was up to the task of tightening the bearings to what felt right without the thread failing. After the second replacement (Capetown), he tightened the blind nut more than he ever had before (no torque value remembered), and things have been OK since (though the roads ridden since have also been much better).
  16. hardwaregrrl

    hardwaregrrl ignore list

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    This isn't good news......:eek1 I'm thinking that the next time I have to change the bearings, I will be pressing this stem out and putting a bmw stem in. I'm hoping to be riding next weekend some nice off road routes up in N. Carolina!!

    Ps sorry about the cold....eat lots of raw garlic!!!



  17. ontic

    ontic

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    Paraphrasing others is always a little risky, buy yeah, bad news and OK news I suppose.
    Bad news- seems to be don't run them too loose or you will probably have problems. OK news- that top blind nut can probably take a bit more torque than it feels like it will- I don't know how much, and don't quote me on that:D
    If Marcus' bike has been OK since Capetown, with this same set up and a more heavily torqued blind nut- then things may not be so bad at all.

    I'll be setting mine with the longer threaded blind nut that I have and torquing it up until I get the right feel and fall away point (which is the only way it makes sense to me, not a ktm manual talking about lighter (mass) and 'smaller' contact angle bearings). I suspect on mine this will be around and possibly over 35-40 ft-lb torque (and whatever it is I'll take note). There is a fair bit of usable thread in the top of that stem (not utilised by the short thread blind nut) and using the longer threaded nut did change the feel of torquing it up for me.
    One thing Marcus also mentioned is that he thought of getting a steel blind nut (bought or machined). Maybe one of the steel swing arm doo-dads with the same thread could be modified and used?:D

    Personally, at this point, I still wouldn't be planning on a stem swap- I doubt the situation is that dire- my feeling is we've got a blind nut and threaded stem system that is not ideal for the torque required to preload our bearings, but that by carefully exploring into the margin of safety designed into this stem, it can be made to work.

    About the cold, thanks. I haven't been sick for over a year and a half, so it is kinda hitting me hard.
    And garlic, yeah, I'm due for another dose. I'm on ginger lemon and Echinacea tea now. I also make a killer chicken soup (very heavy on the ginger, garlic and chilli) and I am trying to muster the strength to head down to do some shopping to cook up a pot full.
  18. Airhead Wrangler

    Airhead Wrangler Long timer

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  19. hardwaregrrl

    hardwaregrrl ignore list

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    Thanks AW....i just don't like the female threads on the stem. From a repair standpoint, it makes more sense to me to have male threads. It certainly is easier to seat the bearing. Off to work on the bike. Been riding 90 miles round trip and no problems or loose front end.!
  20. ontic

    ontic

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    Started to recover from my flu today so considering I've taken today and tomorrow off work(:D) I got a bit busy.

    I think I may have figured out part of the reason I am having trouble preloading my bearings properly, I'll get to that at the end.

    First I set about shortening my forks.
    Nothing new to show here that Solo hasn't already. Thanks to his write up and PM's it was pretty easy. I have shortened them by the full length of that black spacer. I'm not sure if this is exactly spot on for G/S measurements, but it feels pretty close.

    here are the 'special tools' I improvised.
    Protaper bar risers with two layers of leather around the cartridge tubes and clamped in the woodworking vice.

    [​IMG]

    worked great.

    next, that damn triple pin thing- I just found some rollers from an old needle bearing from my 4x4 that fitted perfectly and then a couple of vice grips and some heat applied around the thread, and it turned and cracked the the thread easily enough.

    [​IMG]


    Some time soon I'll have to go to the trouble to actually make that special tool- I just didn't have the patience tonight (as it is going to have to be a pretty good fit to work well). At the least, next time I'll find my other set of vice grips so that I can use three pins instead of two.

    Not much different here to Solo aside from the colour of the PVC pipe I used for my new spacers. Well, they are KTM forks aren't they:lol3
    As you can see, new spacer same length as the black spacer that is being removed.

    [​IMG]

    [​IMG]

    Did both forks, put it all back together, and we now have a much shorter front end- suddenly the side and center stands work again.

    I haven't loctited the few threaded bits that seem to want it inside the forks as I will only be running them like this for some testing- and pretty soon they'll be pulled apart again and probably lenthened a little bit and who knows what else before I put them back together for the final time.



    Next I set about exploring the old blind nut and bearing preload issue.

    First off I made a steel blind nut out of a swing arm thing out of my spare parts.
    A little bit of welding and grinding and what not,

    from left to right is, the old KTM aluminium blind nut with the long thread, the new KTM aluminium blind nut with very little thread, the steel blind nut I made with maximum thread that will work in the stem (pretty much exactly the same as the nut on the far left), last to the right another of the swing arm things I made the nut out of.
    [​IMG]

    new long thread steel nut vs new short thread aluminium nut- the washer on the steel nut is aluminium and is from the old KTM aluminium nut I have.

    [​IMG]


    [​IMG]


    After making my new steel blind nut I torqued my head stem right up... pretty damn high (over 60 ft-lb:eek1)and it didn't do much-
    what I think I figured out is that the top of my stem is probably hitting the bottom of the washer under the blind nut before my torquing up of the blind nut preloads the bearing enough.


    I did a test with some soldering wire under the washer between the washer and the top of the stem, torqued it up, and sure enough the very thin soldering wire got squashed.
    It is not too clear but that is squashed thin soldering wire on top of the washer there.

    [​IMG]

    Why this is happening to me?
    At present I have not fitted a top bearing cover because I need to cut it down in order to get it to fit with my scotts damper pin tower- it is quite possible that the tolerance on this stem is that tight that this very thin removal of spacing between the bearing and the triple clamp means that I haven't been able to preload my bearings properly.
    Hopefully this will be fixed when I fit my bearing cover, and if not then I will make up a washer/spacer thing (to go under the blind nut washer but around the top of the stem) that will let me pull the stem a little bit further into the top triple clamp. Does that make sense? (I hope so)



    Besides all this, after all my thought into the different bearings issue- I still feel quite sure that we need to torque our bmw bearings a bit more than the KTM manual calls for.

    I also tried my suggestion of keeping the bike on the centre stand and loosening the lower triple fork tube pinch bolts and the upper triple stem pinch bolts, and then torquing up the blind nut, and it worked much better for me as the nut was no longer having to pull the entire front end up.

    Cheers,