Stripped bottle cage bolt thread - best workaround?

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DrJeffers
Posts: 57
Joined: Tue Apr 07, 2015 8:21 pm
Location: Wiltshire, UK

by DrJeffers

I've got a rattling bolt on one of the bottle cages of my Pinarello FP3. The bolt screws in fine most of the way, but once all the way in it keeps on turning and won't fully tighten. It then rattles annoyingly when riding. The boss itself is not loose in the frame, just the threads. It's definitely the boss threads that is the issue, not the bolt itself - which i have tried changing.

My question is - what's the best way to approach? I was thinking of buying an M6 tap (current thread is M5) and tapping it out to a larger diameter then using an M6 bolt for that mount. Is that the most sensible way forward, and would there be any issues with the different thread spacing (0.8mm for M5, 1mm for M6)? Anyone done this successfully or is there another way? I imagine this must be a fairly common issue.

Many thanks!

joec
Posts: 100
Joined: Wed Mar 05, 2014 9:20 pm

by joec

M5 helicoil IMO

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DrJeffers
Posts: 57
Joined: Tue Apr 07, 2015 8:21 pm
Location: Wiltshire, UK

by DrJeffers

Thanks - no idea how they work, but will look into it! ;)

spud
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Joined: Sat Feb 07, 2009 5:52 am

by spud

if you are sure that the threads are stripped, and that the rivet is not turning in the frame, then drilling will be your only option. You may find that upon drilling, the walls of the rivet get vanishingly thin or it breaks if you try to retap for M6 or helicoil. I'd probably just drill the thing out, collect the scraps in the BB, and install a new rivnut - to get it out, use a large bitt to drill the top flange of the rivnut off - be careful and don't get down into the carbon. Drill slowly until the flange is almost gone/paper thin, then just tap it through lightly with a punch and hammer.

spud
Posts: 1261
Joined: Sat Feb 07, 2009 5:52 am

by spud

on second thought, make sure the BB does not have a solid alloy sleeve inside - you wouldn't want the remnants of the rivnut trapped and rattling around in your downtube.

DrJeffers
Posts: 57
Joined: Tue Apr 07, 2015 8:21 pm
Location: Wiltshire, UK

by DrJeffers

Thanks - hmm, i knew this wouldn't be simple! If taking that approach i might turn the bike upside down instead (heresy!) and remove the seat post, rather than allowing debris to head to the business end...

mike
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by mike

Replace rivet. I would not use helicoil since I don't think there is enough material to grab when drilling out first

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tnkn
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Location: Hampshire, UK
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by tnkn

I had to replace a rivnut on my frame a couple of days ago. Was simple.

Used a very small flathead screwdriver, a hacksaw black and carefully cut away making sure not to touch the frame. I used the flathead screwdriver and hammer to tap away at the rivnut until it fell through the frame. Turned frame upside down to get the rivnut out of the seatpost tube.

Bought a rivnut gun and a pack of m5 rivnuts from amazon for £20. Job done!

Probably not a recommended method but worked for me.

wingguy
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Joined: Thu Mar 08, 2012 11:43 pm

by wingguy

spud wrote:on second thought, make sure the BB does not have a solid alloy sleeve inside - you wouldn't want the remnants of the rivnut trapped and rattling around in your downtube.


Doesn't matter much if the bike has a BB sleeve or not, bikes tend to have bloody great holes in the headtube and seattube, do they not? :wink:

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toiyuet
Posts: 174
Joined: Wed Dec 14, 2011 2:47 pm
Location: Hong Kong

by toiyuet

We don't need a rivnut gun at all, just use a QR and some spacers.

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Last edited by toiyuet on Thu Mar 24, 2016 11:10 am, edited 1 time in total.

DrJeffers
Posts: 57
Joined: Tue Apr 07, 2015 8:21 pm
Location: Wiltshire, UK

by DrJeffers

Thanks all, really helpful thoughts.

joec
Posts: 100
Joined: Wed Mar 05, 2014 9:20 pm

by joec

I was assumeing the FP3 has bonded in threaded inserts BTW,

DrJeffers
Posts: 57
Joined: Tue Apr 07, 2015 8:21 pm
Location: Wiltshire, UK

by DrJeffers

Well, they look like the ones in the pics above! Doesn't look anything particularly fancy.

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pavel
Posts: 69
Joined: Mon Jan 04, 2016 12:03 am

by pavel

toiyuet wrote:We don't need a rivnut gun at all, just use some QR, and mant spacers.

wow, brilliant.

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