Rear Bearing failure / Damaged swingarm

[Marius]

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,

Marius

 

[Cooter]

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:eagerness:

TL;DR
Replace the arm.

 

[Marius]

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

 

[Endopotential]

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?

 

[zanzibar]

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.

 

[Marius]

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

 

[Cooter]

(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:upset:

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:sorrow. 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:up:, 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):eagerness: 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:up: The front is: 20/ spin/ settle the suspension/ 40...

 

[Marius]

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

 

[Cooter]

$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?

 

[Marius]

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?)



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

Swingarm out:


Little helper (especially for transporting broken down bikes):


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.

 

[zanzibar]

Hi Marius,

for as low as 65 bucks I would sure change it and keep mine as spare.
As far as you sure to get a good one and right for your bike.
Standoff is just the place where left inner race stop when you thigh axle.
If you get it 1/8" shorter you will move your whole assembly 1/8" to left.(your is probably not shorter, just badly worn outside)
You will get problem with wheels alignment, belt, and probably with brake caliper.
But if the inner race is stopped there you still will able to thigh everything together.
Wheel bearings on your bike are not designed to work with preload and you will not have it if you don't over thigh the axle so much to crash the inner spacer.
Only the left side outer race is bottoming in the rim seat, the right one will stay in the position determinate by inner spacer length that is slightly bigger than the distance between outer races seats shoulders. As is correct to be with your type of bearing, no preload, but few 1000s of side play.
So said, buy off course the used one ad change it.

 

[zanzibar]

(Sigh) I think we found a new TP-Hawk...

I spent a live as mech. technician, just discovered this forum, not enough to understand your quote.
But enough to understand you are so full of gas that you fart more with your mouth than your ass.:down::down::down:

 

[user_deleted]

marius: i keep the below NEW factory and aftermarket parts in stock at near my original dealer cost for board members if needed. PM me if you need anything. i'm in southern PA. so you can either swing by and pick up or shipping would be cheap to any other point in PA.

front rotors
rear rotors
front and rear brake pads
front and rear wheel bearing kits
swingarm bearing kits

DAVID: regarding your axle/bearing question....both the front and rear XB axles and clamping surfaces are a thing of beauty both in design and simplicity. my only complaint thru the decades has been the excessive belt tension, which can be addressed and rectified very simply. the wheel placement....alignment...bearing preload...and correct installation is a brilliant and well-engineered design. it goes like this: both sides of both rims have a bearing pocket. each pocket has a small lip or "floor" that the bearing bottoms out against. each wheel has an inner bearing spacer which looks like a long thin tube. the left interior swingarm side has a built-in spacer....the right side does NOT. that spacer is part of the axle. the axle shaft itself is tapered on both ends like a funnel. when everything is assembled correctly and within factory tolerances and specs.....you install the axle from the pulley side and it engages threads machined into the swingarm on the rotor side. yet another nice piece of engineering on buells' part. as the axle is installed and gently starts to tighten the "funnels" feed themselves thru both wheel bearings which centers the wheel and begins to move it up and back and snug everything up including the belt.
lastly....when the axle is torqued to spec it has not only aligned everything but has now become a complete "fixture". the "fixture" in other words, is the axle...the inner bearing races....the inner wheel/bearing spacer. it is now all clamped together which allows the wheel assembly to freely rotate around the fixture. and what is everything clamped "against"? the spacer that is part of the inner left side of the swingarm....and the spacer that is part of the right side of the axle. that's as simple as i can explain it.

 

[Endopotential]

Thanks John, another mystery of the universe solved!

I'm honored to be part of the first-name club now :angel:

 

[zanzibar]

DAVID: regarding your axle/bearing question....both the front and rear XB axles and clamping surfaces are a thing of beauty both in design and simplicity. my only complaint thru the decades has been the excessive belt tension, which can be addressed and rectified very simply. the wheel placement....alignment...bearing preload...and correct installation is a brilliant and well-engineered design. it goes like this: both sides of both rims have a bearing pocket. each pocket has a small lip or "floor" that the bearing bottoms out against. each wheel has an inner bearing spacer which looks like a long thin tube. the left interior swingarm side has a built-in spacer....the right side does NOT. that spacer is part of the axle. the axle shaft itself is tapered on both ends like a funnel. when everything is assembled correctly and within factory tolerances and specs.....you install the axle from the pulley side and it engages threads machined into the swingarm on the rotor side. yet another nice piece of engineering on buells' part. as the axle is installed and gently starts to tighten the "funnels" feed themselves thru both wheel bearings which centers the wheel and begins to move it up and back and snug everything up including the belt.
lastly....when the axle is torqued to spec it has not only aligned everything but has now become a complete "fixture". the "fixture" in other words, is the axle...the inner bearing races....the inner wheel/bearing spacer. it is now all clamped together which allows the wheel assembly to freely rotate around the fixture. and what is everything clamped "against"? the spacer that is part of the inner left side of the swingarm....and the spacer that is part of the right side of the axle. that's as simple as i can explain it.

:up::up: Fully agree and Very well explained, Thank you.
Just right side bearing outer race is supposed to get very close to the "floor" but not fully bottom it.
Right side Inner race must bottom with inner spacer just a bit before.
Do you agree?
Anyway great explication.:applause::applause:

has been the excessive belt tension, which can be addressed and rectified very simply

Any suggestion you can give us?

 

[user_deleted]

my pleasure david. thank you zanzibar for the compliment. and yes sir...you're correct.
i put a light coating of general purpose grease on the outer shell of each wheel bearing....the inner spacer tube....the axle itself but NOT the threads. NEVER EVER apply a coating of grease to a bearing pocket that has a "lip" or "floor" to it, such as an XB. i have seen a few thru the decades that had this done during assembly and as the bearing was driven in, the grease was pushed against the "lip/floor" and actually hydraulic'ed.... and not only broke out a portion of the bearing pocket but put a hairline crack in the rim.
on the REAR WHEEL you install the rotor side bearing first till it bottoms against the bearing pocket floor....then flip the wheel over having the pulley side facing upward. drop in the inner spacer tube....then press in the bearing till the inner race contacts the spacer tube. you can hear and feel it when that happens. you MUST keep the spacer tube straight so that correct contact between it and the inner race is achieved. just get it close. the axle will do the rest once the wheel assembly is installed and axle torqued to spec.

belt tension???? remove a few millimeters of of material at arrows. lessens the tension.

 

[Marius]

Good to know! Thanks for the suggestions.

Also, can one of you take a look at the pictures of my rear wheel and let me know whether the inner spacer on the rotor side looks the same as the inner spacer on the belt side, or whether there are differences. I am trying to determine whether the wheel is shot as well!?

Thanks,

Marius