Helicoil "How-to"? for Derailleur Hanger, Help!

jvanv8 · Jan 20, 2008

I managed to strip out the derailleur hanger bolt threads on my frame. I have extra bolts but it appears that the frame threads are stripped.

The hole is extremely small and probably only has 3 "threads" for a bolt to bite into.

- Is it possible to do a Helicoil job on this? I don't know anything about heli coil except that I've heard it mentioned in forums when bolts are stripped.

- Can I fix the thread with a helicoil kit myself? or do/should I have a pro do it?

- How are these things sold? Do I get a kit and find the right size or do I order the exact size I need ahead of time?

- How can I determine which size the bolt is?

OR ____
- Do I get a tap and retap it? (I have no idea how to do this either but maybe it's easier)

Thanks guys!
John

DERMotorSports · Jan 20, 2008

First, what material is the frame? Is the rear derailleur replaceable?

Assuming it is steel or Al and NOT replaceable, the next question is how mechanically adept are you? This is important - cause a screw up here can be bad; so if not very adept at all, take it to a pro. If adept, you'll need to size the hole - rd is standard so no issue there. Then you'll have to purchase the kit from HeliCoil or a decent hardware store - when in doubt, try http://www1.mscdirect.com/CGI/NNPDF...MPAGE=408&PARTPG=GSDRVSM&PMT4NO=36229472&PMITEM=00068361&PMCTLG=00&PMT4TP=*LTIP.

The kit will contain everything you need except a drill. Just follow directions or call here: 770.631.0125

The HeliCoil site is at:http://www.emhart.com/products/helicoil.asp

Dan Law
dermotorsports@gmail.com

kidd546 · Jan 20, 2008

If there is enough metal left to re tap you can just run a tap in the hole. More than likely there is not enough metal left.Wheels Manufacturing has repair kits that have you drill the hole out then place a nut through the back side and bolt the dérailleur in place. But first check and see if your frame has a replaceable hanger, this is the easiest way.

jvanv8 · Jan 20, 2008

The frame is aluminum and yes, the derailleur hanger is replaceable. The screw is the one that holds the hanger to the frame. The bolt goes through a hole in the hanger and secures inside the frame... which is stripped. It's super small and probably can't protrude too much out the end since it would interfere with the cassette.

As far as mechanical knowledge.. I basically have done all my own bike maintenance for the past 10 years without going to a shop... but I've never dealt with stripped bolts before.

Thanks for the link on the helicoil kits. Great resource.

So is it confirmed that helicoil is what I need to do and not tapping a new thread?

android · Jan 20, 2008

jvanv8 said:
The frame is aluminum and yes, the derailleur hanger is replaceable. The screw is the one that holds the hanger to the frame. The bolt goes through a hole in the hanger and secures inside the frame... which is stripped. It's super small and probably can't protrude too much out the end since it would interfere with the cassette.

As far as mechanical knowledge.. I basically have done all my own bike maintenance for the past 10 years without going to a shop... but I've never dealt with stripped bolts before.

Thanks for the link on the helicoil kits. Great resource.

So is it confirmed that helicoil is what I need to do and not tapping a new thread?

I'm not sure that you would need a helicoil here because it doesn't matter if you go to the next size bigger screw to hold the hanger to the frame. Just find out what the next larger screw is and drill and tap to that size and then bolt the hanger back to the frame.

You have to use a helicoil when the bolt HAS to match an existing bolt such as a derailleur bolt to hanger connection. Since that is standard, you can't go to a bigger size.

A specialty fastener store can help you out. Most major cities will have one. Look under fasteners in the yellow pages and take them your broken stuff. They'll find you something close, but you may have to file or grind off the protruding end to clear the cassette.

Cheers! · Jan 21, 2008

Yes it is possible to fix the threaded hole on your frame via helicoil. I would let a pro do it. The helicoil kit (which contains, correct drill size, helicoil, helicoil tool) will run you what it would cost a good bike shop to fix. The size is probably anything from an M4 to M6 metric thread fine.

Personally I would fix it rather than drill out the whole and convert it to a through hole for a nut bolt arrangement.

Touch0Gray · Jan 21, 2008

my experience with helicoils is that they work best in a deeper, close bottom hole. correct me if I am wrong but to put a helicoil in, you drill the hole out to the "next size" larger and tap the hole to allow the thread on the outside of the helicoil to thread into the new, re-tapped hole. The bottom of the coil has a "tab" that the inserter catches to screw the coil into the new hole from the bottom, (it resembles a slinky" and winding it in from the top causes it to expand and NOT go in properly.
The inside of the helicoil is the matching thread for the old bolt. What will hold the helicoil in place while the bolt is screwed back in to it, particularly if there are only like 3 threads holding it in?

all my bikes have a brazed or welded der. hanger, but my son's mtn bike has a bolt on hanger, and there is a bolt, with the head on the inside (wheel side) and a lock washer and nut on the outside. would that work for you? Even if you had to grind the head down a bit to avoid catching on the cassette.....

Cheers! · Jan 21, 2008

At work (aerospace engineering) we use helicoils in similar applications. The number of threads engaged is a lot more than 3 since it is a fine thread metric fastener. Typically the thickness of the dropout which the hanger bolts onto is 1/4 to 3/8" thick. Good enough for atleast 6+ threads to be engaged. I have not seen how bicycle shops install said helicoil into small threaded holes such as this application. But we apply helicoil primer that dries to help "glue"/secure the helicoil to the new tapped hole. Certain types of epoxies work as well. Again your mileage may vary, and different companies make helicoil kits/types for different applications. Surf around for one that is adequate for your needs. Or just drop the bike off at your most trusted local bike store with a 6 pack of beer.

Touch0Gray · Jan 21, 2008

i was wondering if epoxying the coil in would be of any benefit...

Cheers! · Jan 21, 2008

Touch0Gray said:
i was wondering if epoxying the coil in would be of any benefit...

It can. Be careful which you choose because some are too "runny" some are too "thick" causing the epoxy to bleed through to the internal threads. Less is also more in this case. Use sparingly, and also make sure everything is cleaned with strong solvents to remove oils from fingers etc.

jvanv8 · Jan 21, 2008

Hmmm, I wonder about the epoxy idea too, although a bolt is more functional. But really the hanger doesn't see much stress at all. It just keeps it in place and keeps it on the bike when you remove the wheel.

Since pictures are always better, here are a few... the frame in the picture is identical to the frame in question (I had 2 frames but the one in these pictures was hit by a car

)

Its a road frame so keep in mind that the derailleur tab is very thin.

Finding a specialty fastener store might be tough... I'm currently in Europe so I'm not sure how available some resources may be. I can always import a helicoil kit and the drill and tap is easy to find anywhere, right?

DERMotorSports · Jan 21, 2008

Be very careful if using epoxy - it's pretty damn permanent. If done right it is great; if wrong will be next to impossible to ever remove and possibly look crap. In this case, I would use an easily redoable solution like standard HeliCoil. Another solution is "ThreadSert" but more expensive. Oh yeah, if buying the Helicoil kit, all the ancillaries are included and you need only provide the electric drill (taps, tools&c are in the kit).

Touch0Gray · Jan 21, 2008

ok, I'm confused...that picture looks to me like it is the rear dropout that is bolted on....does it hold the wheel in as well as the der.?

android · Jan 21, 2008

From the photos, I see no need to spend money on a helicoil. Just tap the hole to the next bigger size and get the next bigger screw. You use a helicoil when you have to have the same size hole. There is no requirement for that here.

DERMotorSports · Jan 21, 2008

Oh yeah, IF you do go the HeliCoil route. There are different lengths of coils AND the coils can be cut shorter so as to be flush with the surroundings once installed - we do this often to custom fit. Typically we only use HeliCoil in non critical fasteners (just our policy has nothing to do with litigation just our beliefs).

dougfdny · Jan 21, 2008

dropout savers

this will solve your problem.any reputable shop should have em...or get them here..http://www.wheelsmfg.com/products.php?cat=tools&prod=framerepair

litespeedf1 · Jan 22, 2008

Last I checked, Loctite was used to secure the helicoil in place The specific type Loctite depends on the specific application. Check with Loctite website.

Cheers! · Jan 22, 2008

dougfdny said:
this will solve your problem.any reputable shop should have em...or get them here..http://www.wheelsmfg.com/products.php?cat=tools&prod=framerepair

That looks like the wrong product for the intended application. The link you have posted looks like it is meant to fix dropout/dérailleur hangers that are not replaceable. The original poster's issue is that he is unable to mount a new dérailleur hanger onto his frame because the threads for the screws that secure the dérailleur hanger are damaged.

Thommy · Jan 22, 2008

I'd go with what Android has to say. Next size up and a flush mounting screw will get you riding again. Pretty common break (glad these do what they're designed to do), easy fix. I've seen a lot of this with mountain bikes. Kudos to dougnyfd for the info on wheelsmanuf dropout saver (couldn't remember the name of the product). Definitely locked that into my favorites. If you used an epoxy between the frame and dropout (for lack of a better word) the breakaway feature might not happen and you might eat a derailleur in the event of an accident. Hope you can resolve the issue. By the way, what kind of frame is this?

jvanv8 · Jan 22, 2008

Hi Thommy, the frame is a FetishCycles but I think other companies also use/brand the design

Actually the hanger did not "work as designed" (meaning the hanger didn't break off in some catastrophe)... it just came loose and I tightened the screw a little too much (which actually wasn't very much). With so few threads and soft aluminum it's easy to do I guess.

I'm going to see if I can find the translation for a "screw tap" to see if I can locate one around here.

Helicoil "How-to"? for Derailleur Hanger, Help!

jvanv8

DERMotorSports

kidd546

jvanv8

android

Cheers!

Touch0Gray

Cheers!

Touch0Gray

Cheers!

jvanv8

DERMotorSports

Touch0Gray

android

DERMotorSports

dougfdny

litespeedf1

Cheers!

Thommy

jvanv8

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