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Thread: Rear Bearing failure / Damaged swingarm

  1. #1
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    Rear Bearing failure / Damaged swingarm

    Hey everyone,

    I have been riding 2006 Buell XB9SX for about 4 years now and rarely ever had any issues with the bike, today however, things were different.
    I noticed an odd vibration while riding today, since it did not go away I decided to pull over and check the bike. I originally expected the issue to be a motor mount or some such thing, but it turned out that the left rear wheel bearing was completely shot.
    It basically had disintegrated to the point where there were no balls left and I could only see the outer race and a gaping hole.

    After recovering the bike I took the rear wheel out.
    Obviously I will replace the axle, the spacer, the bearings (also in the front) and am thinking about replacing the swingarm as well.
    However, the reason why I am asking whether that is actually necessary is because I am not 100% clear about the function of the swingarm in pre-loading the bearings inside the rear wheel.
    What do you think will happen if I was to use the same swingarm with new bearings etc?

    And oh yes, the wheel ran in such a wobbly way that the break disc chewed up the brake caliper mount ... I have no idea how the rear wheel did not lock up and how I didn't crash, but I certainly am not complaining!

    Thanks,

    Mariusdamagebearing3.jpg

  2. #2
    Senior Member Cooter's Avatar
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    Ouch! Thats bearings been bad for many miles. You will love how your bike rides and handles once it back together.

    I'm normally a 'save it' kind of guy, but in your case I would add a replacement swing arm to the list for sure. It looks like the depth dimension of that standoff (basically a built in spacer) has been compromised.

    The way the spacer/axle/inner bearing race is clamped together, that dimension is critical for proper bearing torque without side loading the ball-bearings in the wheel. If that dimension is shortened like in your case (or more commonly a over-torqued spacer), the outer wheel bearing races will bottom out in the wheel and you will continue to have pre-mature bearing failure until you fix it correctly. Usually mis-diagnosed as 'Brand A bearings suck, get brand B" when all you need is the correct space dimension.

    Follow the manual instructions exactly for proper torque, and procedure and you'll be OK. Get that .pdf download for free at Buellmods.com or Buelltooth.com. Hows the wheel hub look? Was the rear rotor over heated? Are the rear pads worn crooked now?

    IMO, I replace wheel bearings every time I put on new tires. Barely any extra labor and worth the small parts cost for 'trip insurance'

    Check the classifieds here for a good arm or PM Purpony, he usually has a bunch of good parts and is a stand-up guy

    TL;DR
    Replace the arm.

  3. #3
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    Thanks for the reply!
    I wonder for how long the bearing has been bad. Not too long ago (somewhere around 3k miles) I changed the rear tire and the bearing felt fine, but I noticed today that around the bearing area on the wheel / brake rotor there are definitely rust stains ... so I am sure it must have been quite crumbly in there for a good while.

    That makes sense, I will open a thread in the classified section and have already checked on eBay. Seems like swing arms aren't exactly expensive nor in short supply.
    And as far as I can tell it is pretty easy to replace them and I will be able to also change the swing arm bearings at the same time!

    The rear rotor does not show signs of overheating, no bluing or anything. I might replace it anyways together with the pads ... after owning Vespas for a while I tend to brake an awful lot with the rear brake

    Yes, apparently doing the bearing replacement as insurance is a good idea, especially since the bearings cost next to nothing, you never stop learning!

    Thanks again,

    Marius

  4. #4
    Member Endopotential's Avatar
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    I've never quite understood how the design of the rear wheel axle works, in that tightening it pulls the wheel back and tightens the drive belt.
    Are the holes in the swingarm aligned eccentrically, or does the taper of the axle somehow drive the wheel rearwards as you screw it in?

  5. #5
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    Marius,

    my opinion is different, so is better you get a third one, and you choose for yourself.
    As far as the swing arm damage is what can be seen on your pic, I would not change it. (is that around 1/4" deep or less?)
    I will have machined the worn part just enough to get again a nice flat and axle orthogonal surface.
    Add a well done spacer, right thickness to get back to the right original length. (you will need to check it on a good condition swing arm).
    That 'stand off' dimension is not critical for bearings side preload.
    It is critical to correctly put wheel on the longitudinal plane of the bike.
    What is critical for bearings side preload is the spacer in between of them inside the wheel hub and the right torque.
    Make sure your is still in good condition and torque to the spec.

    Side note. (I am sure you would now like to develop a better understanding on how a bike must behave when you ride. It's almost impossible to believe you did not fell anything bad before to get so far in damaging)


    or does the taper of the axle somehow drive the wheel rearwards as you screw it in?
    exactly like that.
    And 'somehow' is that when you first screw in the axle the inner race of the right bearing is on a much smaller diameter.
    This allow the wheel to be misaligned toward losing the belt so to permit to install it.
    As the taper (that is going to reach 30 mm diameter) get on the inner race is of course slowly pulling back the wheel in alignment reaching so the right tension of the belt.
    Not fully sure what is going on the left side bearing (I'll check next tyre change) but axle design and bearing clearances, should permit to don't hurt anything.
    Unusual system but it works.
    I have installed a Free Spirit spring tensioner that is simplyfing a bit operations and seems to help a bit bearing and belt lives.
    Last edited by zanzibar; 09-28-2019 at 09:15 AM.

  6. #6
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    Hmmm, what would happen if the standoff had been worn short, if the it is not important for the pre-loading?
    If the standoff is too short, is the wheel then able to slide on the axle towards the missing amount of standoff? And so to avoid that I would have to add a spacer?

    And yes you would think that I should have felt something being wrong with the bike for a long time, but I didn't and I actually ride a lot and know the bike fairly well.
    One of the only things I felt was an unusual vibration which started appearing about 70 miles ago, it felt like a broken motor mount but certainly not like a failing wheel bearing. The oddest thing about it is that it came and went, so pulling the clutch to check whether it was actually caused by the engine sometimes related with the vibration and sometimes didn't.
    Even yesterday when this all happened I didn't feel too much that was unusual. The one thing that I did notice was that cornering made the bike feel as if the rear tire was skidding... of course I should have checked at that point but alas I didn't. I did check when the vibration was persistent and here we are

    My current course of action is to replace the bearings (duh!?!), replace the spacer (it doesn't look great) replace the axle (it is probably fine but won't hurt).
    I will also buy a new swing arm and will measure what the length of a good stand-off is and compare it with my current one.
    If there is no large discrepancy I will make sure the surface is square and probably mount it with the old swing arm / potentially including a spacer and see what the rear wheel feels like.
    Otherwise I will get rid of the swing arm and in the same vein also replace the bearings for the swing arm.

    All in all an annoying experience that could have ended A LOT worse ... but as always a lesson learned!

    Funny thing is, my wife's Buell Blast had a bad rear wheel bearing and it was immediately obvious what was going on. How I was oblivious to the issue for a good while is a total mystery to me!?

    Marius

  7. #7
    Senior Member Cooter's Avatar
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    (Sigh) I think we found a new TP-Hawk...
    If the swing arm stand off is too short (like it looks in the pic)... what are you tightening the bearing assembly against? Air? You would be over-torquing the rear axle and the wheel would be slightly off to the left. Belts don't love that either

    The standoff/ left inner wheel bearing race/ bearing spacer/ right inner bearing race/ axle flange assembly must act like one solid piece when tightened. Much like the front axle stiffens the front fork assembly, the rear axle also stiffens the swing arm when tightened properly.

    Marius: Yes, you could make a custom "orthogonal" spacer (LOL). But you'd have to have another swing arm disassembled and in in your hand to measure properly, AND you would still need to machine the stand-off on your existing worn swing arm to square, and then machine the correct spacer...

    Unless you have a micrometer and a lathe in your garage like zanziorthogalbar does, why the heck not install the good arm thats already in your hands

    You are doing fine and you sound capable enough to make this an easy job, don't get confused by that post.
    Like you said, swing arms are cheap and plentiful, so why not do it right? With new pivots, it should last the life of the bike (for half the trouble) Heck, you could put on a longer Ss swing arm like the cool kids do!

    Your wife has a Blast? Sweet! Bubbles and I just finished one

    Endo: Yep, its the taper on the rear axle shaft that allows both the rear wheel inner bearing races to have clearance while the axle is backed off, relieving pressure on the belt. Thats why the torque to 25ft/lbs- spin the wheel- back off 2 turns- re-torque to 50ft/lbs procedure for the rear is so important The front is: 20/ spin/ settle the suspension/ 40...
    Last edited by Cooter; 09-28-2019 at 07:11 PM.

  8. #8
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    Yeah as much as I love making stuff, machining that spacer would probably take me twice as much time as taking the swingarm out and putting a new one back in.

    And that makes sense that the wheel would move over to the left. Turns out I just bought a swingarm on eBay for 65 dollars... hard to beat!
    Speaking of that, how many different versions of the swing arm exist? (not in terms of long ones and short ones, but are there some that fit some model years and not others? i.e. did the normal length ones change over the different model years?

    That is a nice looking Blast! My wife's looks very basic and happens to be her first bike but it is quite a fun bike, albeit a bit shaky

    I will now finally make my way down into my garage to take out the old bearings and remove the old swing arm... I actually wanted to be on my way to a PawPaw festival in PA ... but instead I am doing garage stuff at home, nonetheless the XB hasn't let me down in over 27k miles and this is my first bigger issue with her!

    Thanks,

    Marius

  9. #9
    Senior Member Cooter's Avatar
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    $65 is a total win!
    Good to hear she's been a nice ride for ya Theres some lower shock mount differences between the different length arms, but I believe any XB arm will bolt on any XB frame.
    There's a few different looks over the years, but only 2 different wheelbases that I know of Hopefully someone who knows definitively will chime in?

  10. #10
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    Swingarm is out (shockingly easy!) I am slightly confused as to what the weird pinch bolt construction is i.e. what kind of an odd nut is at the bottom of the pinch bolt

    Bearings are out of the rim. I think the side of the rim where the wheel bearing failed is shot. As far as I can tell this calls for a new rim as well :eyeroll: ...
    Only way to get the outer race out of the left side of the wheel hub was to weld the inner race onto the outer race and drive it out.
    The good side of the rim has a slightly raised surface on the outside and a lower wider surface on the inside that clearly has been machined in that way in the factory.
    The bad side does not have that lower wider surface anymore (or did it never?)
    good side.jpg
    bad side.jpg

    The swingarm I bought is from a 2008 XB9SX so it should fit without any changes!

    Swingarm out:
    swingarm out.jpg

    Little helper (especially for transporting broken down bikes):
    HY.jpg

    I think I will add a new rim (do they come with bearings installed?) and a new brake rotor / pads to the list. The outside of the rotor has some bluing going on that I could only see in sunlight, so it looks like it overheated.



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