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Broken Bolt

Here is my 2 cents on this subject . I sold fasteners for over 20 years , by looking at the pictures it's possible that MOCO may have a warranty issue here due to some bad fasteners . I'm guessing at the size but they look like 1/2" . The min. tensile strength of 1/2" g8 bolts are 150,000 psi , the shear strength is 21,300 psi and the torque spec is 106 ft.lbs. A few yrs. back Peterbuilt had some bad g8's that sheared for cuasing the stering to malfunction , this could be the case , but if they just worked loose that would be a whole different story .
 
They dont appear to have backed out although they could have. If you look at the 5 bolts they are different lenths so maybe they did work loose. You can see 2 of the bolts are rounded so they probably broke first and wore as I drove on them more after they broke.
 
To me picture #3 indicates the bolts were loose and they rocked back and forth for awhile. If the bolts sheared without having been loose 1st,, the holes would not be elongated like they are in picture #3.
They now look like slots rather than holes. If the bolts just sheared, those slots would be nice looking round holes.

To me they got hammered to the point of shearing.
 
Hoople, that makes sense. To me the question is WHY did this happen and what was the cause. The only thing I can think of since there were never any modifications to the rear wheel is this is a MOCO issue.
 
BOWHIKER said:
Here is my 2 cents on this subject . I sold fasteners for over 20 years , by looking at the pictures it's possible that MOCO may have a warranty issue here due to some bad fasteners . .. .. .. .. ..
Click to expand...

Hoople said:
To me picture #3 indicates the bolts were loose and they rocked back and forth for awhile. If the bolts sheared without having been loose 1st,, the holes would not be elongated like they are in picture #3.
They now look like slots rather than holes. If the bolts just sheared, those slots would be nice looking round holes.
To me they got hammered to the point of shearing.
Click to expand...

I feel like they sheared themselves off on the swingarm as I have heard about many times in previous posts. And yes I have often thought about the strength ratings of a Grade 8 bolt (which they are stamped Grade 8). I cannot track the info down, but it seems I read somewhere that the shanks on these bolts were designed to shear off (when backed out and hitting the swingarm) to prevent a wheel lockup and possible death. It may just be hear say, but that is what I remember reading. I don't know how it would be possible from an engineering design standpoint to still have a grade 8 bolt that would still shear at the shank. So whatever there.

Anyhow they've been on my pre-ride inspection now since last November when I first started reading about it.
 
Wow...makes me want to go out & check my bolts. Bet that was quite a ride/noise when she let go - ouch!
 
R_W_B said:
but it seems I read somewhere that the shanks on these bolts were designed to shear off (when backed out and hitting the swingarm) to prevent a wheel lockup and possible death.
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If that was the case, the shear point of the bolt would not be on the thread. Looking at picture #5, it shows the bolts sheared on the threaded portion.
A designed shear point would probably never be put on the threaded area.

My take on the entire event is those 5 bolts have been loose for a "long" time.
Not saying since the bike was made but they did not come loose the morning this happened. Those pieces have been rocking back & forth for some time.

Is that a virgin assembly since the bike was built? Has anyone taken the assembly apart in the past for any reason. My Dyna does not have a system like that, so I am not familiar with reasons for removing it or taking it apart (ie tire change,,, belt change,, rear wheel bearings replaced etc).
 
Hoople said:
My take on the entire event is those 5 bolts have been loose for a "long" time. Not saying since the bike was made but they did not come loose the morning this happened. Those pieces have been rocking back & forth for some time.
Click to expand...


You may be on to something although I never felt anything out of the ordinary and when the all finally broke, due to me going <10 MPH it was like your bicycle chain fell off.
 
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