Destroyed my Swingarm, take my advice.

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BMW didnt want you to use any air tools on their steeds! You can rip out threads loosening bolts too, electric has a softer hit and a better trigger feel, but the batteries adventually take a shit...no free lunch. And NO, 1/2 impact wrenches on those nuts! You could do the lugs if it werent your bike though :evil:

 

Shit Tink, now we all feel bad ........ I'm giving my self a time out

 

That's the spirit, Jason. This is a forum full of very helpful (but sometimes quite smart assed) people who are extremely into all things VFR.

My best guess is that the self-locking nuts backed the stud out just enough that when you tightened it back down you might have shouldered on the stud. You thought you had it tight, but as the paint wore the space allowed oscillations (along with the vibrations from the chain) and it backed out. We all have to remember that EVERYTHING on a motorcycle is a safety issue and do visual inspections regularly.

Jose

 

Not every stud requires thread locker. In this case tightening the nut on the sprocket pulls on the stud. Tightening the stud in the hub.

I think your right about the paint. The sprocket could also have been misaligned from excessive/ uneven paint.

 

IMO if you were really concerned, you'd loan him a torque wrench.

 

No shit...............

 

Jason I know we were a little harsh with ya---buts its because we CARE dam-it. But I do think you should change your user name to sledge hammer ----ya know like Peter Gabriels song ----come on, what do ya think ?otstir:

 

That is amazing and good that you were not hurt.
Considering how cheap the torque wrenches are in the USA I think it would be a sound investment.
The paint on the sprocket does look very deeply worn in the photo, as said above maybe that gave enough slack for vibration to loosen the stud.

 

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Second from the right looks like a Proto, probably calibrated to 2-3% accuracy.

 

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Jason, do yourself a really big favor and give up on the whole "they were properly torqued to 85lft/lb".............................using a damn hammer. The fact that you keep going on about your super torque sensing arm/hand and sledge hammer and your super human mechanical abilities that would seem to put Nobby Clark to shame, make you sound like a politician that's been caught red-handed pulling something shady and blathering on that it was OK. Just give up on the "Hammer Time" theme.
The fact that you loaded up so much paint on the sprocket AND the cush drive shows me (a rider/racer/mechanic of 39 years) you don't know much as you think you know. I guess would would have, at least before this little episode, painted a rotor carrier and the hub, and then been amazed that something went awry .
Now, all that BS being said, sprocket bolts and nuts are one of the items on a bike that are the most susceptible to thread fretting.

Chris

 

Show me how you ruled it out... Seriously... The fact that it took 85 to undo the nut is irrelevant from both a physics and engineering perspective... An exercise we did at trade school involved hand tightening an alloy wheel to a hub using correct torquing technique... Now that wheel required ~130Nm as per manufacturers handbook, from memory it took less than 100Nm to undo some of those lug nuts - this leads me on to failing wtuds from over torquing... Well documented the world over and Nissan probably had one of the most telling issues with it... The handbook for the Nissan Patrol had the upper torque limit something silly like 10 or 12Nm higher than it should have for the alloy wheels... This was enough to lead to stud fatigue and the damned things were losing wheels all over the place - that's right, over tightening saw both lug nuts undoing themselves and studs literally snapping in half...

Striking anything with a sledge creates moments of extreme shock on the systems involved... We are dealing not only with studs on which our lives potentially depend, but also a joint between dissimilar metals and the alloy casting in which the studs mount will likely fatigue first, as is evident by your studs coming out rather than the nuts coming loose...

 

Crap! I just traded my torque wrenches for a bag of hammers and a rusty wrench set. There's no way he'll trade me back. I'm screwed.

 

All I know is that I went out at looked at my bikes' swingarms after seeing these pics. Scary!

It's also a reminder that the pre-ride equipment check is smart.








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