Suspension Fatboy 2007 lower fork pinch bolt snapped

spakey

Club Member
Enjoying a nice ride with fellow Region 19 guys with just a few clouds in the sky and I seem to be getting spots of what I thought was rain in the face. The A31 is not the best surface to run on and I guess the front suspention was working fairly hard, anyway the next bit of bumpy 'repair' surface I have a huge explosion of oil. Pulled over and I was drenched in fork oil all down the right side. On the Fatboy you can't see any of the fork stanchion or seal caps as it's concealed by the tin ware so the assumption was an oil seal had blown. With this assumption I decided that the front suspension would be somewhat degraded but I'd be OK to continue, we're heading for the Wheels Day, Rushmore Arena Aldershot. A great day at the show and normally we'd take the scenic route via a hostelry on the way back but I said to PP (my wife Pauline) I think we'll make our own way home (there's no way the rest of the guys will do 35-40 miles an hour all through the back lanes of Hampshire!)

So I get the bike back home and to be honest I wasn't convinced that much oil would get past the seal, anyway removing the tin ware I find this:

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The oil seal was in fact OK but the lower yoke pinch bolt has snapped and the stanchion had 'unwound' itself from the top nut.

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Obviously the bolt snapped some time previously and the stanchion had unwound over a period of time but I'd not noticed as the it's all covered in the tin ware. The front suspension hasn't been touched since new as the fork oil change isn't due for another 10k miles. As you can see the upper yoke arrangement is not the normal pinch bolt type so the stanchion is clamped only by the lower yoke. On any other bike without the tin ware this failure would be obvious, so if you have a Fatboy it may be worth adding these bolts to the critical fasteners check list.
 
Re: Fatboy 2007 lower fork pinch bolt snapped

A truly shocking failure, and a lucky escape from what could easily have been catastrophic Steve. Glad to hear that you n Pauline made it home safely.
I applaude you for posting this mate. It'll get others taking a look at their ride and could potentially save someones life.
Hodgie.
 
Re: Fatboy 2007 lower fork pinch bolt snapped

Scary shit. Worst thing was though we had to put up with him smelling like an oil slick for the day.

Sent from my SM-G903F using Tapatalk
 
Re: Fatboy 2007 lower fork pinch bolt snapped

I'm surprised a bolt that size failed. My experience of Harleys is they are well over engineered, at least shovels and flatheads's. In fact when compared to Jap equivalents they are almost industrial. Maybe it was an assembly issue? Either way, glad you got back ok.

Rod
 
Re: Fatboy 2007 lower fork pinch bolt snapped

Is it true Steve that you are now offering this system as a franchise opportunity for waterproofing jeans? ������
 
Re: Fatboy 2007 lower fork pinch bolt snapped

Is it true Steve that you are now offering this system as a franchise opportunity for waterproofing jeans? ������

Yes mate, with a special 'eau de oilette' :D
 
Re: Fatboy 2007 lower fork pinch bolt snapped

While on a ride out in Yorkshire over the August bank holiday I too had suspension problems very similar to the original post.. luckily I was in my camper and could get my Softail back to the Midlands. Ordered oil seal kit from Mark at Barnaby Wild,and the tool from Andy tool sec. On starting the job I found the top plug un wound on the left side! The right side pinch bolt was sheered and the left one was loose....I suggest all owners check the condition of the forks onSoftail models as soon as possible!
 
Re: Fatboy 2007 lower fork pinch bolt snapped

Nasty! Two very similar incidents with potentially dangerous consequences. Should this be reported to VOSA Vehicle Safety Branch, Croydon St, Bristol, BS5 0DA?

This may be useful. Bolt Science don't recommend spring washers nowadays as they aid loosening and bolt failure.
http://www.boltscience.com/pages/vibloose.htm
Conventional spring lock washers are no longer specified, because it has been shown that they actually aid self loosening rather than prevent it.
And.
Often fatigue failure is a result of the bolt self-loosening which reduces the clamp force acting on the joint. Joint slip then occurs which leads the
bolt being subjected to bending loads and subsequently failing by fatigue.

Best use plain washers and loctite.

Hope that helps.



 
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Re: Fatboy 2007 lower fork pinch bolt snapped

Nasty! Two very similar incidents with potentially dangerous consequences. Should this be reported to VOSA Vehicle Safety Branch, Croydon St, Bristol, BS5 0DA?

This may be useful. Bolt Science don't recommend spring washers nowadays as they aid loosening and bolt failure.
http://www.boltscience.com/pages/vibloose.htm
Conventional spring lock washers are no longer specified, because it has been shown that they actually aid self loosening rather than prevent it.
And.
Often fatigue failure is a result of the bolt self-loosening which reduces the clamp force acting on the joint. Joint slip then occurs which leads the
bolt being subjected to bending loads and subsequently failing by fatigue.

Best use plain washers and loctite.

Hope that helps.




Depends on the application. Its an oversimplified analysis of a complex science. Internet science at its best.
 
Re: Fatboy 2007 lower fork pinch bolt snapped

As a retired engineer I always fitted spring or lock washers ( they are different beasts) on mainly railway equipment and I have never known a bolt to sheer because of them. And believe me a Euro star vibrates more than a Softail!
 
Re: Fatboy 2007 lower fork pinch bolt snapped

Internet science at its best.
I agree that it pays to be careful but in this case it would be easy to check. The company is based in Chorley - they cite NASA, Ford, ALSTOM, Triumph and Harley among others as clients - give them a bell.
It seems the effect they reported above was based on research done at the [FONT=Verdana, Arial, Helvetica, sans-serif]Jost Institute of Tribotechnology at the University of Central Lancashire. [/FONT]
 
Re: Fatboy 2007 lower fork pinch bolt snapped

I agree that it pays to be careful but in this case it would be easy to check. The company is based in Chorley - they cite NASA, Ford, ALSTOM, Triumph and Harley among others as clients - give them a bell.
It seems the effect they reported above was based on research done at the Jost Institute of Tribotechnology at the University of Central Lancashire.

Step away from Google!
 
Re: Fatboy 2007 lower fork pinch bolt snapped

I already have, I use DUCKDUCKgo. :wink:

If you fancy some interesting bedtime reading, here is the engineering PhD on bolt loosening that identified the 'Jost' effect above:
http://clok.uclan.ac.uk/6649/2/Eccles William Final e-Thesis (Master Copy).pdf

The research was done in 2010, so it's pretty recent. Hope it helps towards resolving the stanchion pinch bolt loosening issues.

Safe riding.
 
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Re: Fatboy 2007 lower fork pinch bolt snapped

I already have, I use DUCKDUCKgo. :wink:

If you fancy some interesting bedtime reading, here is the engineering PhD on bolt loosening that identified the 'Jost' effect above:
http://clok.uclan.ac.uk/6649/2/Eccles William Final e-Thesis (Master Copy).pdf

The research was done in 2010, so it's pretty recent. Hope it helps towards resolving the stanchion pinch bolt loosening issues.

Safe riding.

Non of which applies to this application. Please stop posting random stuff you have found on the internet to try and add content to something you know nothing about. Its misleadind and has no relevance to this important subject. If you are a qualified engineer and have experience of fastner applications thats great but anyone can search the internet and find stuff which is not relevant or even misleading.
 
Re: Fatboy 2007 lower fork pinch bolt snapped

Thanks Alex. Glad someone actually read it. It is interesting isn't it. Loctite found the same. It seems to be rather more than a coincidence.

Phil, if I may. The research I highlighted shows that fasteners with spring washers are more likely
to loosen with transverse vibration. The stanchion pinch
bolts had spring washers, the bolts loosened.
Personally I use Loctite. Loctite also supply test data on spring washers loosening. I have a research
background and
would welcome (no sarcasm intended) your lines of thought on the matter and why this research is not relevant?

At the end of the day, I am not the one with loosened and broken stanchion pinch bolts. It's not something any of us want to happen. The prospect is frightening.
Most important is finding a solution.
 
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Re: Fatboy 2007 lower fork pinch bolt snapped

The research I highlighted shows that fasteners with spring washers are more likely to loosen with transverse vibration. The stanchion pinch
bolts had spring washers, the bolts loosened.
.

So where is the transverse vibration/shear loading on a pinch bolt. The two surfaces are part of the same piece, there is no relative shear loading or shear vibration. Its purely a tensile force. It may have a cyclic element but its still tensile. It is also not a nut and bolt, it is a bolt into a threaded hole.

No research needed.

End.
 
Re: Fatboy 2007 lower fork pinch bolt snapped

Thanks Phil that's helpful. Would the split surfaces not be subject to transverse movement under conditions of cycling?
 
Re: Fatboy 2007 lower fork pinch bolt snapped

The pinch bolt pinches. it does not take side loads, as it does not actually clamp surfaces together as there is residual a gap usually.



In the original post the pinch bolt had snapped (not worked lose)

IMHO... the reasons are

1) bolt over/under tightened at the factory (possible)
2) bolt faulty manufacture (possible)
3) bolt of the incorrect grade (improbable)
4) bolt overloaded through accident damage (improbable)
5) bolt incorrectly refitted at some stage during a service operation (possible)

Its a small bolt, and the tightening torque is quite low. Its easy to get it wrong if you do not use the correct specification. Very easy to over tighten.
 
Re: Fatboy 2007 lower fork pinch bolt snapped

After reading the post by Four Speed I have looked up some of the findings of the people who have run tests. I have decided that in some applications it is wise to use Locktite . So...job done, new bolts, oil and seals. Back on the road,now I am going to check my fault codes....
 
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