# Broken Bolt... in my Fork



## rose (Sep 29, 2006)

So, not having a torque wrench, I broke a bolt off in the fork of my bike.

Now, what do I do? A quarter of an inch of the bolt is broke off inside the fork mount, and it looks like I also striped out another 5-6 threads.

The questions I have: 

How do I get the bolt out?
How to tap/drill new treads in?
Where can I get another bolt?
Is the fork ruined?
Is this something I need a bike shop to do for me?
Can anyone recommend a reputable bike shop in Hawaii?


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## cobba (Apr 5, 2007)

Are you sure that the bolt is broken ?

Are the bolts are from the fork's post mounts where the brake is attached ?

Do you have a 185mm rotor ?

Notice in the following photo with the 185mm post mount adapter that one end of the adapter is larger then the other end.










2 different length bolts are fitted in the photo above, you can see them in the following link.

Avid CPS Hardware Kit for 185mm Rotor - AEBike.com

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## rose (Sep 29, 2006)

Cobba, very good point, thanks! I didn't notice that before. After further inspection of the bolt, it did not break off, so that's very good.

However, I definitely stripped out the treads. How can I fix that?


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## nov0798 (Nov 27, 2005)

Well, even though this isnt the "right" way to do it, itll work! Look for some tappable epoxy.

Products - Belzona

Probably the 1831 product Super UW metal would be best.

You will need to fill the hole with the epoxy, let it harden( it hardens like steel). 
NOTE: Take the depth measurements of the hole BEFORE you fill it with epoxy. An easy way to remember the depth is to place the proper sized drill bit in the hole, and back off maybe an 1/8 to 1/16th of an inch. Place a piece of tape around the bit as a flag of where to stop. Remember to take this measurement with the caliper mount in place!

Once the epoxy has hardened (24 hours) then use the caliper mount as a guide, and drill the epoxy to the appropriate depth. Dont drill through the fork tube!
Tap the hole back to the correct size, and you should be good to go.


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## cobba (Apr 5, 2007)

rose said:


> However, I definitely stripped out the treads. How can I fix that?


Are you talking about the threads in the middle part of the bolts that look to be worn down ?

If you are then don't worry about it. Those threads don't screw into anything, the brake adapter, CPS washers and the brake are positioned on the top 2/3 to 3/4's of the bolts. The end 10mm to 15mm or so of threads on the bolts ( the threads with whitish residue ) that actually screw into the fork post mounts are the only threads on the bolt that are really used.

Some aftermarket bolts only have threads on the end part of them as you can see in the following link.

Avid CPS Hardware Ti Torx 25 XX for 185 post - AEBike.com

If you stripped the threads in the post mounts on the for fork that would be a different story. The threaded post mounts on forks are either made out of magnesium or aluminium which are both softer metals then the steel that the bolts are made out of, it would be much easier to strip the threads in the post mounts then it would be on the bolts. Don't over torque the bolts when replacing them.

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## nov0798 (Nov 27, 2005)

Those bolts shown dont have threads to the top. Those bolts are shouldered.


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## paetersen (Jul 28, 2007)

nov0798 said:


> Well, even though this isnt the "right" way to do it, itll work! Look for some tappable epoxy.
> 
> Products - Belzona
> 
> ...


That's like the hardest way possible to fix this problem. A solution exists. It is time-proven, easy to implement and widely available. It even results in a repair that is stronger than the original threads and is pretty hard to bugger up whilst implementing.

Heli-Coil. Get some. Use them, love them. When you are done you will have spring-steel threads instead of prone-to-galling-and-stripping-out aluminium threads.


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## cobba (Apr 5, 2007)

nov0798 said:


> Those bolts shown dont have threads to the top. Those bolts are shouldered.


The OP's bolts look like they were fully threaded at one stage too, it looks to me like part of the threads have been filed/ground down.

The reason why the OP's bolts are probably like they are.............

There's been a few posts/threads I read where people have had problems fitting a post mount brake onto a post mount fork with a 185mm post mount adapter. The problem could be that the post mount adapter was poorly made and holes don't run parallel or that the threaded holes in the post mounts aren't parallel. Anyway what ends up happening is the further out the bolt heads are from the fork post mounts the greater the centre to centre distance between them becomes. 
The 74mm centre to centre at the fork post mounts might end up being 76mm centre to centre at the bolt heads with the longer bolts and the adapter fitted.

A few ways people have fixed the problem:
* File out the holes in the adapter to make them bigger.
* File down the threads on the bolts where adapter and caliper sit. 
* File out the mounting holes on the caliper to make them bigger.

A thread about this problem: Stuck trying to find a 185 adapter for 74mm post mounts

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## nov0798 (Nov 27, 2005)

I am well aware of Heli Coil, and Time Serts. The problem with these is that you must drill the hole bigger, and then retap to the new size to insert them. IF the material where these mount on to the fork is not thick enough, then you will break the mount off, meaning you will need to replace the fork. My suggested method keeps the wall thickness the same. 

The bolts in question were never threaded to the top. As Ive said before they are shouldered bolts, and offer more strength than a completely threaded bolt. There is no reason to thread the entire bolt, as it doesnt thread into anything up that high anyway.

I would NOT file anything down to make the hole bigger. The problem isnt with the fit of the adapter, he said he stripped the threads, which means he over tightened the bolt.


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## cobba (Apr 5, 2007)

nov0798 said:


> The bolts in question were never threaded to the top. As Ive said before they are shouldered bolts, and offer more strength than a completely threaded bolt.


Yes shouldered bolts would be stronger but.....












> There is no reason to thread the entire bolt, as it doesnt thread into anything up that high anyway.


True, maybe you should complain to Avid about their fully threaded bolts.

Fully Threaded Bolts: Avid CPS Hardware Kit for 185mm Rotor - AEBike.com



> I would NOT file anything down to make the hole bigger.


That's your choice but plenty of people make small modifications on things to get them to work.



> The problem isnt with the fit of the adapter


It might of been the original problem, some threads might of been damaged trying to fit something that wouldn't fit.



> he said he stripped the threads, which means he over tightened the bolt.


5 to 6 threads were quoted as being stripped. 
I could be wrong but doesn't more then 5 or 6 threads on the bolt actually screw into the post mount ?
If this is the case why were only 5 or 6 threads stripped ?


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## gmcttr (Oct 7, 2006)

cobba said:


> ...5 to 6 threads were quoted as being stripped.
> I could be wrong but doesn't more then 5 or 6 threads on the bolt actually screw into the post mount ?
> If this is the case why were only 5 or 6 threads stripped ?


Just a thought...use the short bolt in the upper post (widest part of the adapter) and you might have only 5-6 threads engaged making it easy to strip.


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## bad mechanic (Jun 21, 2006)

cobba said:


> Yes shouldered bolts would be stronger but.....


Thank you! The "shoulder bolt" thing was driving me crazy, and was debating correcting it myself.

Also, I don't understand why someone would use the epoxy over a Time-Sert. There's plenty of wall thickness there, and the bolts aren't under tension during braking. People have been Helicoling and Timeserting forks for years now with good results. With the epoxy you're going to run the risk of voids, insufficient adhesion, and making sure you drill the hole straight. While it's a good solution for certain problems, this isn't really one of them.


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## rose (Sep 29, 2006)

Thanks for everyone's comments. After calling around to a few bike shops, Helicoling is the way to go. Unfortunately, I couldn't find a bike shop here in Hawaii who a) knew what I was talking about, or b) had done it, or was willing to do it. If I was back in the mainland it wouldn't have been a problem-
I ended up buying another fork and will try and sell this one on eBay for parts. Anyone interested?


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## bad mechanic (Jun 21, 2006)

Installing a helicoil isn't hard, and you could easily do it yourself. Just follow the directions.


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## nov0798 (Nov 27, 2005)

The marks come from turning the bolt in the hole. Lok at any shouldered bolt that has been taken in and out several times, and they all look like that, especially if the hole there in is at its proper dimension. Those are not stripped threads. If it were threaded in that area, the threads wouldnt thread into anything anyway, so what would strip them? Looks like SRAM had some shouldered and some threaded bolts for the adapters. The only thing I can guess is that the fully threaded bolts are cheaper, and the strength isnt needed, so they opted for the cheap way out. The shouldered section is in Red, and the threaded section is in Green.


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## bad mechanic (Jun 21, 2006)

nov0798 said:


> The shouldered section is in Red, and the threaded section is in Green.


Those aren't shoulder bolts, they're just partially threaded bolts. On a shoulder bolt the unthreaded section section increases in diameter with defined step between the threaded and unthreaded portions:


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## nov0798 (Nov 27, 2005)

bad mechanic said:


> and the bolts aren't under tension during braking.


Im not starting a flame war here, but just wondering why you say this? How could those bolts NOT be under a load while braking? If the bolt is torqued to its proper torque, then it is under tension. Under braking forces, these bolts are under alot of load with the caliper trying to tear them away from the fork.


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## bad mechanic (Jun 21, 2006)

nov0798 said:


> Im not starting a flame war here, but just wondering why you say this? How could those bolts NOT be under a load while braking? If the bolt is torqued to its proper torque, then it is under tension. Under braking forces, these bolts are under alot of load with the caliper trying to tear them away from the fork.


I didn't say they're not under load during braking, just not under tension. Take a look at the direction the caliper applies force to those bolts. There'll be some sheering loads, but the bolts won't come under tension. Look at the picture below. The brake force will try to push the caliper up and forward, not back.


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## nov0798 (Nov 27, 2005)

Yes the example you gave are other variations of shouldered bolts. These are sometimes also called shanks instead of shoulder(tomato, tomato')but the execution is the same.The bolts in the picture given by the OP are also shouldered bolts. Quick search of google gives this definition.

A part of a screw or bolt below the head that has no thread and provides a smooth surface that can tightly mesh with an object. Designed into the screw or bolt. Can be various sizes
shoulder, screw shoulder, bolt shoulder definition

The difference between shoulder screws and other types of screws lies in how far up the threading - the ridges that spiral up the shaft of the screw and draw it into the hole as it turns - goes. On normal screws, the threading goes all the way up to the head of the screw. On shoulder screws, the threading stops a distance from the head, leaving a smooth-sided round or square shaft between the threading and the head. This shaft is usually slightly larger than the threaded portion of the screw.
What are Shoulder Screws?


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## bad mechanic (Jun 21, 2006)

The bolts pictured aren't shouldered by any definition of the word. For a shoulder bolt to be a shoulder bolt, the diameter steps out from the threads, and in those pictures you can actually see the diameter decreases. McGraw Hill defines (as does the less accurate Wikipedia) it as:
_A screw with an unthreaded cylindrical section, or shoulder, between threads and screwhead; the shoulder is larger in diameter than the threaded section and provides an axis around which close-fitting moving parts operate. _​
So not only does the unthreaded portion decrease in diameter, but the interface between the unthreaded portion of those bolts and the caliper is not a precision fit either. So, again, those are not shoulder bolts, only your run-of-the-mill partially threaded bolts.

EDIT: Also, a "shank" and a "shoulder" are two separate things. They are not the different terms for the same thing.


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## nov0798 (Nov 27, 2005)

That really doesnt really give a true representation of the forces that are applied, since the rotor is turning, the forces are all over the place. Hey prove me wrong, leave the bottom bolt out, and go stop, itll probably bend the caliper and the top bolt right up around, and probably break off. This would prove that the forces do push/pull on those bolts

Bottom line is the bolts pictured are shouldered, shanked, whatever you wish to call them. Well ok shank refers to the entire length below the head, some are unthreaded and are called "grip" length / shoulder length / etc.


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## nov0798 (Nov 27, 2005)

OK so here are some what I called shouldered bolts. Per your definition, they are larger in the shoulder area then the thread area. Even your definition calls then shoulders?? If you take a solid piece of steel and thread it, but then stop half way up to create a shank/shoulder/ whatever the threaded area will always be less diameter then the unthreaded section. The bolts appear to the naked eye to be the same diameter throughout, but they are not as the caliper shows. I can guarantee you that the OP bolts are larger in diameter in the unthreaded section than the threaded section. So per your definition, they are shouldered bolts!


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## cobba (Apr 5, 2007)

nov0798 said:


> I can guarantee you that the OP bolts are larger in diameter in the unthreaded section than the threaded section. So per your definition, they are shouldered bolts!


The earth is flat too I suppose.


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## bad mechanic (Jun 21, 2006)

nov0798 said:


> That really doesnt really give a true representation of the forces that are applied, since the rotor is turning, the forces are all over the place.


No, they're not all over the place. The forces and their direction are quite easily calculated. It's not magic, it's physics.



nov0798 said:


> Bottom line is the bolts pictured are shouldered, shanked, whatever you wish to call them.


No, it's not whatever you wish to call them. They're technical terms, and they have specific meanings. If you're going to use them, use them correctly, otherwise you're giving out incorrect and bad information.

Regarding the bolts, you're really trying to stretch your argument any which way to not be wrong, aren't you? Instead of continuing to dig yourself deeper, just accept you didn't have it right, and be happy you learned something new today. Stop being aggressively ignorant.

Buy the way, rolled threads will generally have a larger diameter thread than the unthreaded portion of the shank.


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## paetersen (Jul 28, 2007)

^^^^Lots of Win here.^^^^


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## cobba (Apr 5, 2007)

nov0798 said:


> The marks come from turning the bolt in the hole. Lok at any shouldered bolt that has been taken in and out several times, and they all look like that, especially if the hole there in is at its proper dimension.


The loosely fitting CPS washers and caliper would be positioned where the 'marks' are.
Do you really think they caused these ground down thread like markings ?
How many times do you think these bolts would of been turned in and out for the loosely fitting CPS washers and caliper cause these marks ?



nov0798 said:


> Those are not stripped threads.


I didn't say they were stripped threads, I said that the threads look like they have been filed or ground down.



nov0798 said:


> If it were threaded in that area, the threads wouldnt thread into anything anyway, so what would strip them?


Obviously it must of been the loosely fitting CPS washers and caliper by your reckoning.












nov0798 said:


> Looks like SRAM had some shouldered and some threaded bolts for the adapters. The only thing I can guess is that the fully threaded bolts are cheaper, and the strength isnt needed, so they opted for the cheap way out.


Avid's 'shouldered' bolts are made from Titanium and the unthreaded 'shaft' looks to be a similar diameter to the thread peaks which is *totally* different to the OP's bolts, Avid also makes stainless steel bolts but they are fully threaded like their standard black bolts.










See this caliper below that couldn't be fully bolted down.
The person who had this problem solved it grinding or filing down the threads on the bolt.
Notice the similarities between the following bolt with ground down threads and the OP's bolts ?
I think there even looks to be the faint remains of a thread on it too.










The OP mightn't of ground down the bolts but whoever originally installed the caliper might of had the same problem as above and did a similar thing.


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## SgtBaxter (Jul 2, 2011)

I've never seen so much discussion and bickering over a photo of something where there's nothing wrong to begin with.

So I'll just toss this out there: You're all completely wrong!!!!!! 

Those aren't bolts at all, they're machine screws. Bolts connect with a nut, and don't have screw drives incorprated into the heads.


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## paetersen (Jul 28, 2007)

Yeah, I was just going to add that I can't believe there is so much bickering over a photo from a guy who can't turn the macro function on.

The OP photo is clearly of a rolled thread bolt that isn't threaded all the way. As was pointed out on those bolts (rolled thread instead of cut thread) the 'shoulder' or smooth section diameter is less that the peak of the threads. The marks are commonly seen on coated bolts that are caused by friction between the shaft and the mounting hole.

There are no stripped threads on the OP bolts other than the clearly, if fuzzily, visible remainder of the aluminium threads from the fork that are clogging the lower threads of one bolt.

I call asshattery and will now be leaving this thread.


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## bad mechanic (Jun 21, 2006)

SgtBaxter said:


> Those aren't bolts at all, they're machine screws. Bolts connect with a nut, and don't have screw drives incorprated into the heads.


:lol::lol::lol: Well, that's a big can of worms just opened! Those definitions are definitely varied and fluid, changing depending on the standard being used and the time:
Screw - Wikipedia, the free encyclopedia


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## SgtBaxter (Jul 2, 2011)

bad mechanic said:


> Those definitions are definitely varied and fluid


Not to mechanical engineers!

Those fasteners are turned to fasten, and do not use a nut to hold two separate pieces of material together. They're screws. 

Now true to the layman the term is pretty much interchangeable. Plus there are bolts that are screws, and if you put a nut on a screw it becomes a bolt. Have I confused you yet? :thumbsup:


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## nov0798 (Nov 27, 2005)

SgtBaxter said:


> Those fasteners are turned to fasten, *and do not use a nut to hold two separate pieces of material together*. They're screws.
> 
> *and if you put a nut on a screw it becomes a bolt*


Bolt versus Screw Definition

:madman:


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