anyone else with this probl? solutions? triangle pivot bolt

[waldo]

my triangle/swingarm pivot bolt broke yesterday. as you can se on the pictures this is a hollow thru axle bolt wich is realy poorly designed...
i mean the wall thickness is 1.5mm and about 1mm where it went off due to the threads.
now im wondering if anyone knows if there is a updated version of this bolt? (@Specialized Rider Care, @SPECIALIZED)
because im worried that its just a matter of time and this will hapen again if you just replace it with a new one.

 

[Zimmerframe]

There was an older thread about this ... looks like spesh generally send out a replacement on warranty ..

Chainstay pivot bolt- Kenevo - EMTB Forums

 

[steve_sordy]

Similar thing happened to me on my Focus Jam2. It was the lower shock mounting bolt, sheared in the same place as your bolt. But mine was a solid bolt. The cause of my problem was the lack of threadlock at assembly allowing the bolt to loosen. All fixed under warranty.

 

[Mcharza]

If I remember right, it's the same as the battery bolt

 

[Zimmerframe]

If I remember right, it's the same as the battery bolt

Everyone thought it was the same as the battery bolt . @DC101 ordered one to try.... but it wasn't :-( ....

 

[Mcharza]

Everyone thought it was the same as the battery bolt . @DC101 ordered one to try.... but it wasn't :-( ....

So my memory was wrong...or at least incorrect

 

[Zimmerframe]

So my memory was wrong...or at least incorrect

Your memory of what everyone thought it was , was correct ? it's just what everyone thought was wrong.

 

[waldo]

im sure the warranty will cover this but im afraid it will soon hapen again, because i think this is a design flaw.
do you think its a good idea to reinforce the bolt with a solid bar of aluminium machined down to the proper diameter to fit inside the bolt with a snug fit? to hopefully eliminate this problem for good.

 

[steve_sordy]

@waldo Good idea, but it depends upon the failure mode. If it was bending or shear then it will work. Not if it was too much torque. However, I've had another look at the pictures and it looks as though it would work. Easy to try though, any hobby machinist or small workshop could do it. I would secure it with an adhesive though to stop it falling out. Please report back with what you do. Others will be interested.

 

[waldo]

i

@waldo Good idea, but it depends upon the failure mode. If it was bending or shear then it will work. Not if it was too much torque. However, I've had another look at the pictures and it looks as though it would work. Easy to try though, any hobby machinist or small workshop could do it. I would secure it with an adhesive though to stop it falling out. Please report back with what you do. Others will be interested.

will do

 

[waldo]

!
haha i cant help wondering how the thougth process was when designing this bolt, but i can imagine it was something like this: " lets make a hole in this bolt to save some weight(?), because this bolt is just holding 2 vital parts of the frame that is under a lot of stress together"

 

[R120]

Surely you can get a third party out of better quality? My concern with putting a pin in it would be that it fails again.but isn't obvious which could lead to a more catastrophic failure/crash

 

[Zimmerframe]

I don't think they shear because they are underspec'd in the design or that the part is not strong enough. It's a tube dealing with circular forces.

I think the force there is 'relatively' small compared to many of the forces elsewhere on the bike where there are considerably higher impact or leverage forces.

Unfortunately, there is a tendency to over-tighten that bolt, especially in light of reports of it coming loose. Once it's been over-tightened it's in linear stress and will be considerably weaker than it was and, whilst in stress, considerably more likely to shear. Shearing being most likely to occur at the weakest point - where the thread begins and where it's not supported.

 

[Mikerb]

I think that bolt has to be removed to remove the motor.....has that happened with this bike? Not refitting to the correct torque and without a torque seal is the most likely cause of the failure I would think. As Zimm pointed out the force exerted on that pivot is a rotating force, rather than a lateral force. There is no point fitting a bolt to an aluminium structure/thread that has a shear force greater than the material into which it is threaded.

 

[KennyB]

Torque seal?

 

[Mikerb]

Torque seal?

Thread lock

 

[waldo]

I don't think they shear because they are underspec'd in the design or that the part is not strong enough. It's a tube dealing with circular forces.

I think the force there is 'relatively' small compared to many of the forces elsewhere on the bike where there are considerably higher impact or leverage forces.

Unfortunately, there is a tendency to over-tighten that bolt, especially in light of reports of it coming loose. Once it's been over-tightened it's in linear stress and will be considerably weaker than it was and, whilst in stress, considerably more likely to shear. Shearing being most likely to occur at the weakest point - where the thread begins and where it's not supported.

what do you guys mean with circular forces? i have newer heard such a thing in physics and could not find a definition of it. (a force is a straight line vector)
i can only see that there is radial- or axial forces on an axle that results in a shearforce on the bolt/axle.


i think the opposite. i think the force can be realy high. e.g. in a hard landing if you bottom out the suspension or when you jump and land a bit sideways...
the way i noticed that the bolt was broken was that the whole bike was flexing on pedal strokes

about over-tightening the bolt thats something that could have caused this because that results in strong shearforces on the bolt( if it is like @Mikerb says about the motorchange) because my dealer recently changed the motor.

I think that bolt has to be removed to remove the motor.....has that happened with this bike? Not refitting to the correct torque and without a torque seal is the most likely cause of the failure I would think. As Zimm pointed out the force exerted on that pivot is a rotating force, rather than a lateral force. There is no point fitting a bolt to an aluminium structure/thread that has a shear force greater than the material into which it is threaded.

 

[Mikerb]

Virtually all the fixings on a bike are aluminium bolts threaded into aluminium. A steel bolt threaded into ally will cause a corrosive reaction between the 2 metals and also be a complete mismatch of shear force. When threading ally bolts into ally thread the correct torque setting is much more important than steel into steel, and any fixing subject to vibration or a rotation force should consist of clean threads and the application of a thread lock. Your failure was most likely caused by incorrect assembly after your motor replacement allowing the bolt to loosen. Either the bolt seized in the pivot or the thread loosened or both. Once loose it is likely to shear at its weakest point. I suggest you merely obtain a replacement bolt, clean the thread it is going into then apply thread lock on the outer 50% of the thread on the bolt and secure to the specified torque. Provided the receiving thread has not been damaged there is no reason why you should get further problems.

 

[CjP]

My bolt broke within a month of owning the bike. I had issues with rear axle bolts coming loose, linkage bolt also loosening causing the whole rear end to wobble.
Once I got the bolt replaced I checked all bolts every ride and have never had a problem since and I’ve put that bike through the ringer. I know for sure that I have over torqued the bolts and still haven’t broken
anything.

My guess is it’s random or maybe if any other bolts are loose, causing the rear end to sway around then that could cause more stress to the bolt.
Just replace it and check all bolts every ride and you hopefully won’t have any other issues.
That’s my experience anyway.

 

[Zimmerframe]

My bolt broke within a month of owning the bike. I had issues with rear axle bolts coming loose, linkage bolt also loosening causing the whole rear end to wobble.
Once I got the bolt replaced I checked all bolts every ride and have never had a problem since and I’ve put that bike through the ringer. I know for sure that I have over torqued the bolts and still haven’t broken
anything.

My guess is it’s random or maybe if any other bolts are loose, causing the rear end to sway around then that could cause more stress to the bolt.
Just replace it and check all bolts every ride and you hopefully won’t have any other issues.
That’s my experience anyway.

Are you sure you didn't run them loose on purpose, so if you landed sideways, you gained an extra 50mm of suspension movement ??

 

[CjP]

Hahaha that’s how it felt but in different directions. Turns out not the best approach.

 

[Zimmerframe]

Did it feel like this :

 

[waldo]

Did it feel like this :

that is the exact feeling..

 

[CjP]

Did it feel like this :

Yep exactly but imagine that going down a black run. Thought I had a flat but turns out I had a mean frame bashing wobble.

 

[waldo]

i contacted my dealer and a new bolt is now on its way! and im going to send the old bolt to a friend who is a machinist and he will make me a new solid one

 

[Zimmerframe]

Thought I had a flat but

You'd be the first person on this forum to think they had a flat butt..

 

[CjP]

You'd be the first person on this forum to think they had a flat butt..

No I’m aware I have a bubble butt, love my stair climbing!

 

[randycpu]

So help me out: Does "ally" in British English = "alloy" in American English?

I see this in many threads here...

 

[Zimmerframe]

So help me out: Does "ally" in British English = "alloy" in American English?

I see this in many threads here...

Generally slang for aluminium.

But being a slang, is probably abused for aluminium alloys too.

 

[steve_sordy]

i contacted my dealer and a new bolt is now on its way! and im going to send the old bolt to a friend who is a machinist and he will make me a new solid one

What sort of aluminium? Pure aluminium, or one of the usual alloys, or something exotic?