# Repairing a stripped IS-brake rotor mount



## glint (Sep 14, 2011)

So, funny story (not really). I was changing the brake rotor on my front hub, and my (previously unused) torque wrench wasn't clicking. I checked the setting and tightened it a little more, and... a little more... and then it was stripped. I dug out the wrench's data sheet and it has a range of 10-80 foot-pounds, 10-80 inch-pounds. :bluefrown:

It's still tight enough to remove and re-insert, but once it's all the way in it keeps on turning. I could replace the hub, but that seems a bit drastic. Someone on another forum suggested reforming the threads with JB weld (using the oiled-up bolt to shape it), but I'm not sure that would do a very good job in such a small space. I also found reference to "helicoil" taps/inserts, which I've never seen and haven't any idea of their availability. I guess I could also re-tap it to use the next bigger bolt size.

Any suggestions or horror stories?


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## bikerjohn64 (Feb 12, 2012)

glint said:


> I guess I could also re-tap it to use the next bigger bolt size.


^^^Bingo! That is what I would do. It's the safest way not to do much more damage.


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## glint (Sep 14, 2011)

Yeah, that's what I figured. Any idea what that next size would be? It's a Shimano HB-M475, and the diagram does not contain the current size. Hayes seems to use M5 X 0.8 bolts 12.7mm/0.5" long.


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## bikerjohn64 (Feb 12, 2012)

I think that being an International Standard; that is the bolt size for all IS mounts. 
I would find a bolt first that will replace it then tap to that size.


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## Katz (Jan 29, 2012)

glint said:


> ..I also found reference to "helicoil" taps/inserts, which I've never seen and haven't any idea of their availability...


Try mcmaster.com. I'm sure they got them, and they ship quick.

Basically it's just like tapping the stripped hole to the next size, except you screw in a stainless insert in now-larger hole so you can retain the original screw size.

Helicoil kit comes with the correct tap, a few inserts, and an arbor to screw the inserts in.


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## glint (Sep 14, 2011)

One hopes they're the same size; I haven't had time to look up what the standard actually covers. All of the IS rotors and mount lugs/bosses/whatever that I've seen so far are through-hole parts... It's possible (though unlikely) that it only covers the spacing and diameter of those holes, and not the type of hardware slotted into them.

Thanks Katz, for the description - I can see several advantages to that setup but with such a thin insert I wonder how it would compare strength-wise. Do you know if the inserts are the "correct size", or if the bolt threaded into them applies outward pressure like in wall anchors?


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## trodaq (Jun 11, 2011)

Helicoil kit uses a drill, tap and an insert. You drill out the hole, tap it then run the insert in to the hole. Break the tang off and you good to go. Insert is stainless and will be stronger than the original part ever was. Make sure you drill straight. If hole is blind make sure you have the depth to sink the insert, Ive even run them too long. Stretch the end out,cut and reset back into the thrads


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## jeffj (Jan 13, 2004)

You stripped one of the six screws that hold the rotor to the hub?

Don't worry about it. The five remaining bolts will hold it just fine. Many weight-weenie racers use just three bolts.

Coda (the old Cannondale house brand) had a four bolt disc hub that held the rotor just fine.


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## winter (Nov 30, 2009)

jeffj said:


> You stripped one of the six screws that hold the rotor to the hub?
> 
> Don't worry about it. The five remaining bolts will hold it just fine. Many weight-weenie racers use just three bolts.
> 
> Coda (the old Cannondale house brand) had a four bolt disc hub that held the rotor just fine.


And not just 3 bolts, but 3 titanium bolts


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## akacoke (May 11, 2011)

why would people wanna use torque wrench on a bicycle ? you are not building a engine here. its just a bike , its not spinning at 5000 rpm


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## glint (Sep 14, 2011)

While getting the helicoil insert installed would be more tedious, it might also be easier than getting appropriate bolts in a bigger size. I did consider running without that bolt or just saturating it with thread-locker since there's no apparent play. But it still feels like a 16% higher chance of catastrophic failure.


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## Katz (Jan 29, 2012)

glint said:


> ...I wonder how it would compare strength-wise. Do you know if the inserts are the "correct size", or if the bolt threaded into them applies outward pressure like in wall anchors?


As mentioned already, you don't need to worry about its strength as long as the hub has enough meat around the insert.

The bolt/screw does not add any outward pressure. The insert will be at the correct size once it's screwed into the tapped hole, so you can screw in a bolt just like you would in the original hole. You may have to trim the insert a little bit if the tapped hole is not deep enough. Make sure you check it, because it's biotch/impossible to back out the insert.

When a bolt is torqued properly, it will stretch a little bit, applying force on threads in longitudinal direction (not just in this particular case but in general). Since the insert is larger than the bolt, it will spread this force over larger area within the tapped hole, making the whole assembly stronger.


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## zebrahum (Jun 29, 2005)

akacoke said:


> why would people wanna use torque wrench on a bicycle ? you are not building a engine here. its just a bike , its not spinning at 5000 rpm


Gee, I don't know... maybe it's so that they don't strip things? I'm sure that the thread you replied to is not a perfect example of why someone would use a torque wrench on a bicycle.


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## akacoke (May 11, 2011)

zebrahum said:


> Gee, I don't know... maybe it's so that they don't strip things? I'm sure that the thread you replied to is not a perfect example of why someone would use a torque wrench on a bicycle.


whatever you say. seems like you guys know it all. one thing is if he used a normal torx bit or a proper torx for bicycle, he wouldnt strip it.


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## Ranger Radon (Aug 15, 2011)

akacoke said:


> whatever you say. seems like you guys know it all. one thing is if he used a normal torx bit or a proper torx for bicycle, he wouldnt strip it.


I'm with you some of the way.... Torque wrenches should not replace common sense... You have to think about what your doing and feel how much force your applying instead of just relying on some instrument.. Normal handtool without leverage gives good indications.. however for stembolts, topcapbolt, pedals etc. a small torque tool can be a good idea!
that said i dont own one... but my fingers do...


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## zebrahum (Jun 29, 2005)

akacoke said:


> whatever you say. seems like you guys know it all. one thing is if he used a normal torx bit or a proper torx for bicycle, he wouldnt strip it.


Are you truly that idiotic? He didn't strip the hex head, he stripped the threads out of the hub. Torx is designed to resist blowing out the head of the screw and was originally designed for torque limited wrenches and screwdrivers for auto assembly. So by using the proper screw provided with the brake system, the OP pulled the threads out of the hub. Had those bolts been secured to the proper torque every time they were installed this wouldn't be a problem. And even if the bolts were torqued to the proper level it is entirely possible that the metal was fatigued from heat cycling and it would have pulled out no matter what. So yeah, you don't know what you're talking about.


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## trodaq (Jun 11, 2011)

I own about at lest 4 torque wrenches. I use them when I feel I need to, which is a lot less than what the "book" tells you to. That being said. Most people I know should use them a lot more often. Unless you're tightening hardware on a regular basis and have developed a feel for it. You should use a torque wrench. 
The know it all opinoin expressed here has been brought to you by me, and is not nesc. the view of MTBR or its officials


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## dietz31684 (Mar 30, 2010)

Go with the helicoil if you can, they do work great!

I dont think you need to go overboard on a rotor bolt, get a screwdriver with a torx bit and get it tight. Throw a dab of blue lock tight on there if you're worried. I have NEVER heard of rotor bolts being notorious for backing out/coming loose. If it's not carbon it's not getting torqued, YMMV.


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## akacoke (May 11, 2011)

zebrahum said:


> Are you truly that idiotic? He didn't strip the hex head, he stripped the threads out of the hub. Torx is designed to resist blowing out the head of the screw and was originally designed for torque limited wrenches and screwdrivers for auto assembly. So by using the proper screw provided with the brake system, the OP pulled the threads out of the hub. Had those bolts been secured to the proper torque every time they were installed this wouldn't be a problem. And even if the bolts were torqued to the proper level it is entirely possible that the metal was fatigued from heat cycling and it would have pulled out no matter what. So yeah, you don't know what you're talking about.


oh my god. i cant deal with you. you are just full of it

OP stripped it because he used a torque wrench. did you see a thread about anyone pulls out the theads from hub without a torque wrench. why you gotta be so stubborn, would he pull it out with out a torque wrench?


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## zebrahum (Jun 29, 2005)

akacoke said:


> oh my god. i cant deal with you. you are just full of it
> 
> i rebuild , restore cars. i dont really care what you say, im not even reading it


That's ok, I'm not arguing. I'm just informing you that you're wrong. I wouldn't expect you to bother reading a sensible argument against what you're trying to say anyway. When the factory builds a car they use torque calibrated assembly tools so you're doing that wrong too.

Just because you can keep something from stripping doesn't mean that no one should use a torque wrench. Most people don't have a feel for what a properly torqued fastener feels like and most people don't religiously check the tightness of the bolts on their bike. Using a torque wrench is good practice. End of story.


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## glint (Sep 14, 2011)

I know a torque wrench isn't necessary, having replaced my share of bent rotors using nothing but the little 'L' style Torx keys. That being said, if the tool is there, I don't see anything wrong with achieving something closer to what the design specs call for... Presumably they were written up by people with far more precise tools, relevant training, and after a lot of testing. I did not use the correct tool, and I counted on said incorrect tool to inform me of when to stop. The wrench is a lot longer than the key, and when you add that much leverage it dampens the feel considerably.

Anyhow, I'm not going to let the issue hold me up. The other bolts had pre-applied thread-lock from the factory on them, but I applied some fresh stuff to that one. The repair kits on Ebay seem to be the best deal unless I can find one locally, and with the light amount of riding I'll be doing until the trails firm up a bit (and the dunes of sand/salt on the roadways get swept) I imagine I'll be ok until it arrives.


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## trodaq (Jun 11, 2011)

See if your local shop ( motorcycle auto or bicycle) has a helicoil kit and get a price for them to do it. Kits are pricey and you can only do it wrong once . Well, maybe twice.
Its like sex. sometimes the first time is scary, especially when your by youself


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## trodaq (Jun 11, 2011)

I rcvd a rep from someone who stated they agree with my previous point, but torque wrenches should not replace common sense. It got me thinking a bit. First off, common sense isnt common. Secondly, you need to have a base knowledge in place before you can realize common sense.
I've worked in the automotive field for 30 years. In that time Ive removed many broken pieces of hardware and repaired many stripped threads. All caused by mechanics who knew better and didnt need a torque wrench. I insist my guys use a torque wrench on anything that is either going to be expensive or difficult for me to fix. 
I use a torque wrench because it keeps you in tune. Do I use a torque wrench on everything? Absolutely not. However I do have that feel and can not only be very close to spec, but also even on multiple fastners. It not just about tightening to specs. You also have to pay attention to sequence as well.
If you arent doing these kind of things on a regular basis,use a T wrench.


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## akacoke (May 11, 2011)

zebrahum said:


> That's ok, I'm not arguing. I'm just informing you that you're wrong. I wouldn't expect you to bother reading a sensible argument against what you're trying to say anyway. When the factory builds a car they use torque calibrated assembly tools so you're doing that wrong too.
> 
> Just because you can keep something from stripping doesn't mean that no one should use a torque wrench. Most people don't have a feel for what a properly torqued fastener feels like and most people don't religiously check the tightness of the bolts on their bike. Using a torque wrench is good practice. End of story.


i dont get why you always have attitude with me.

you should really look at what other people have to say about this. torque wrench is not necessary , most people dont know how to set it. even tho a 1/4" torque wrench got way more leverage for any bicycle bolt to handle . if you know anything about torque wrenches. you will know all the click type torque wrench is not accurate from 10-20ft.lb. a rotor bolt is 55in.lbs. thats like less than 5 ft.lbs. since you like to mention so much about car. you are comparing bikes to cars. you should ask any mechanic see if they use a torque wrench to tighten a bolt to 5ft.lbs.

let do this. also to add some useful technical info on this thread. if you can say how you would properly set and maintain a click type torque wrench without googling, i will admit im wrong


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## akacoke (May 11, 2011)

also to OP, if you really wanna use a torque wrench. get a decent 1/4 drive beam type with case. 

beam type is best for low torque apps like bikes. with a case it will last forever without having to need re-calibration like the click type. 

if i was you, i wont even bother fixing it. its not that big of deal. on your 5 bolt hub car you can run 4 bolts no problem on freeway.ive seen people run it like that on tracks. you have 6 bolts on your rotor, missing one is really alright.


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## zebrahum (Jun 29, 2005)

akacoke said:


> let do this. also to add some useful technical info on this thread. if you can say how you would properly set and maintain a click type torque wrench without googling, i will admit im wrong


Well I happen to have access to a calibration lab, so that's probably not a valid argument to have.

You can try and back pedal all you want, but the fact remains that there are torque specs in place for a reason. Can you really sit there and suggest that ignoring the fact that the manufacturer suggests a torque range is a good idea?

I understand that you have enough experience that you feel that you won't need to check torque on every bolt, but to suggest to someone who is stripping bolts and owns a torque wrench that they stop using the torque wrench is insane. If you suggested that they check the torque setting on their wrench or learn how to use their wrench then we wouldn't have this disagreement. The same thing applies to every single person who suggests that the torque values be ignored and that someone just goes for "tight".

Trust someone who has stripped a fair amount of bolts learning what proper torque specs mean. Dissimilar metals are the norm in bicycles, torque specs are important because bolts (steel) are put into aluminum parts all the time; we're not talking steel bolts in steel blocks.


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## Ranger Radon (Aug 15, 2011)

trodaq said:


> I rcvd a rep from someone who stated they agree with my previous point, but torque wrenches should not replace common sense. It got me thinking a bit. First off, common sense isnt common. Secondly, you need to have a base knowledge in place before you can realize common sense......
> If you arent doing these kind of things on a regular basis,use a T wrench.


its problably pretty obvious that that person was me..:skep: And I maintain that developing a feel for it goes a long way.... The leverage on a big torque wrench is huge, so the slightest fault in calibration or setting could result in stripping... thats more unlikely with a small handtool without leverage... I find that torque wrenches are most usefull when loads of power is needed ie. 40 NM and over, because you need it properly tight!

on brakes, rotors etc I would never consider using it.. however I would like to have one for doing up my stembolts, so i wouldnt strip the anodizing of my thompson... Because that would scrape of before pulling threads...


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## akacoke (May 11, 2011)

Ranger Radon said:


> its problably pretty obvious that that person was me..:skep: And I maintain that developing a feel for it goes a long way.... The leverage on a big torque wrench is huge, so the slightest fault in calibration or setting could result in stripping... thats more unlikely with a small handtool without leverage... I find that torque wrenches are most usefull when loads of power is needed ie. 40 NM and over, because you need it properly tight!
> 
> on brakes, rotors etc I would never consider using it.. however I would like to have one for doing up my stembolts, so i wouldnt strip the anodizing of my thompson... Because that would scrape of before pulling threads...


rep for you man, thats exactly what i think. to me torque wrench its switching from long handle to shorter handle ratchet, or the distance between the bolt and your hand on the handle when pulling it. im not really familiar with NM, but anything under 30 ft.lbs, i just use a 1/4 drive ratchet . i know for sure most cases i could never over tighten using that size ratchet. but i do use a very well calibrated toruqe wrench on oil pans, cuz they tend to leak when have uneven toruqe or over torqued.


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## akacoke (May 11, 2011)

zebrahum said:


> Well I happen to have access to a calibration lab, so that's probably not a valid argument to have.


im not trying to argue with you, im here to learn and chat, to have a good time

click type torque wrenches should be zeroed after each use,

you would not use it to lose any fastener at all.

when it clicks you dont go over it, or try make it click multiple times

these will all mess up the calibration in a long run. so yall out there with click type torque wrenches. pay attention to these


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## trodaq (Jun 11, 2011)

Ranger Radon said:


> its problably pretty obvious that that person was me..:skep: And I maintain that developing a feel for it goes a long way.... The leverage on a big torque wrench is huge, so the slightest fault in calibration or setting could result in stripping... thats more unlikely with a small handtool without leverage... I find that torque wrenches are most usefull when loads of power is needed ie. 40 NM and over, because you need it properly tight!
> 
> on brakes, rotors etc I would never consider using it.. however I would like to have one for doing up my stembolts, so i wouldnt strip the anodizing of my thompson... Because that would scrape of before pulling threads...


 Still cant figure out why it would be obvious that you left the rep. It was grey, Neither good nor bad. As I said it got me thinking. Nothing more, nothing less.
The conversation keeps turning to how a T-wrench is to big or its only useful in this range etc. A 1/4" T-wrench measure in inch lbs . Mine goes from 40-200. Divide by 12. Thats not a lot of torque. 
We are saying the same thing for the most part. Howevr, the only way to develop a feel is to have a standard.You cant possibly know how tight something is without either a measurement (beam or dial) or a preset value (click type).


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## Ranger Radon (Aug 15, 2011)

trodaq said:


> Still cant figure out why it would be obvious that you left the rep. It was grey, Neither good nor bad. As I said it got me thinking. Nothing more, nothing less.


Cause i wrote this in the post #11.


Ranger Radon said:


> .... Torque wrenches should not replace common sense... You have to think about what your doing and feel how much force your applying instead of just relying on some instrument..


And you wrote this:


trodaq said:


> I rcvd a rep from someone who stated they agree with my previous point, but torque wrenches should not replace common sense.....


at least i thought it was obvious.. but then again, i wrote it 

It was definitely positive... im just lacking in rep.power therefore my acknowledgment to you was unfortunately gray.



trodaq said:


> The conversation keeps turning to how a T-wrench is to big or its only useful in this range etc. A 1/4" T-wrench measure in inch lbs . Mine goes from 40-200. Divide by 12. Thats not a lot of torque.
> We are saying the same thing for the most part. Howevr, the only way to develop a feel is to have a standard.You cant possibly know how tight something is without either a measurement (beam or dial) or a preset value (click type).


I cant disagree with that... I only state that just because you use a Twrench you shouldn't stop thinking about what you're doing.. Clearly one using a wrong twrench should consider how much force they are applying and not just mind-numbingly trust the "clicker"

A twrench has its uses, definitively but I will still maintain that you get a very long way if you put some consideration in to what you're doing... It obvious that the cassette which needs 40 NM ~ 30 ft lbs/350 in lbs has to be tightened more than a hollowtech 2 pedal 12-14 NM ~ 8.85 ft lbs/106 in lbs

I've develop a feel without using the Twrench... have stripped some stuff over the years.. newer on my bike though, because I know it's delicate, and I would rather put my trust in me, than some tool that for all i know might be faulty, hence i dont have means to calibrate said tool.

And while i agree that some delicate carbon parts will be tricky to deal with without a twrench, mounting a rotor to a hub, should not facilitate the use of said wrench..


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## glint (Sep 14, 2011)

I'm glad my post started a lively discussion, but back on topic for a moment. By way of a sophisticated technical survey (aka inserting a toothpick into the bolt hole, then measuring it to find the depth), another possible solution has emerged. 

The bolt hole depth + the thickness of the rotor ~= 17.3mm, and the rotor is 2mm thick. So the bolt hole is roughly 15mm deep. The bolts that I have are a little over 9mm long (not including the head), meaning they only thread into the first half of the bolt hole.

I'm going to probe a little more once I grab a flashlight, but what are the chances the hole is threaded all the way down? If that's the case, simply getting a longer bolt could provide the same strength as the original, in addition to being comparatively cheap.


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## glint (Sep 14, 2011)

It would seem the hub already uses inserts. I used a dental pick to check the solidity of whatever threading was left in the bolt hole; this and several smaller fragments were loose inside. I guess this explains why the bolt still turned normally without needing to be pushed in and pulled out. There still appear to be 3-5 turns of undamaged threads remaining, but I couldn't feel with the pick wether they're still fixed in place or not.

The good part is that the hole itself looks to be smooth-walled, so it will be easier to tap a straight hole if I opt for a thread repair kit. The bad part is that I will probably need that tap to verify whether the existing hole is small enough for it to be used.


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## Ranger Radon (Aug 15, 2011)

glint said:


> I'm glad my post started a lively discussion, but back on topic for a moment. By way of a sophisticated technical survey (aka inserting a toothpick into the bolt hole, then measuring it to find the depth), another possible solution has emerged.
> 
> The bolt hole depth + the thickness of the rotor ~= 17.3mm, and the rotor is 2mm thick. So the bolt hole is roughly 15mm deep. The bolts that I have are a little over 9mm long (not including the head), meaning they only thread into the first half of the bolt hole.
> 
> I'm going to probe a little more once I grab a flashlight, but what are the chances the hole is threaded all the way down? If that's the case, simply getting a longer bolt could provide the same strength as the original, in addition to being comparatively cheap.


Depends on whether you stripped all 7mm of thread or simply crossthreaded some at the bottom .. before you drill or helicoil, start off with a longer screw, try turning it in there with a screwdriver, and make sure you dont bottom out with 3 mm between bolt head and hubflange.

I would start by tapping up the original thread, to make sure any crossthreading was straigthened out,, then i would try the screw and if theres suitable hold, put a dab of blue threadlock on the tip, screw it tight by hand and be done with it...

If you insist on using a Twrench for the job, refrain from doing it with the injured threadhole, because just a little hold is better than no hold... trust your fingers.. and may the force be with you..

sorry for the derail!



glint said:


> The bad part is that I will probably need that tap to verify whether the existing hole is small enough for it to be used.[/QUOTE]
> 
> Get a decent Tapping kit... chance is youll need it again...
> I have a fairly cheap set, as im not using it very often, but it is quite nice to have lying around..
> ...


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