Stripped Thread On Campagnolo Inner Chainring

shortfall
shortfall Posts: 3,288
edited June 2019 in Workshop
I have a 2012 (ish) 11 sp Record 39t inner chainring on which one of the threads stripped when I removed the securing bolt. The bolt itself is ok it's the threaded part of the chainring which has failed meaning I can't tighten it up. There doesn't appear to be enough metal to drill it out and fit a bolt with a securing nut/threaded sleeve so I'm wondering what is the most economical repair? New Campag chainrings look to be pretty pricey. Taking it to a shop to get it drilled out and a new thread tapped in is an option but I wondered about trying some threadlocking compound or similar. Does anyone have any thoughts on the best way to proceed? (No jokes about buying Shimano instead :D )

Thanks

Comments

  • rafletcher
    rafletcher Posts: 1,235
    I think the only people who do compatible chainrings are TA (although I haven't been able to find them online) and Miche - see here..

    https://www.bike24.com/p220050.html

    Those Miche ones might not be the exact match for you, but if you give Malcolm at Thecycleclinic - https://thecycleclinic.co.uk/ - a ring he should be able to help, as he sells Miche stuff and can talk to the importers, Chicken. He's also a Campag pro shop, so will know what you're talking about.
  • shortfall
    shortfall Posts: 3,288
    rafletcher wrote:
    I think the only people who do compatible chainrings are TA (although I haven't been able to find them online) and Miche - see here..

    https://www.bike24.com/p220050.html

    Those Miche ones might not be the exact match for you, but if you give Malcolm at Thecycleclinic - https://thecycleclinic.co.uk/ - a ring he should be able to help, as he sells Miche stuff and can talk to the importers, Chicken. He's also a Campag pro shop, so will know what you're talking about.

    Thanks. I'm going to try some Loctite in the first instance seeing as it's only a few quid and will come in handy elsewhere. I'm not holding out too much hope that it will provide a permanent repair though in which case I'll contact Cycle Clinic.
  • Alejandrosdog
    Alejandrosdog Posts: 1,975
    Is the thread totally stripped or just damaged?

    If damaged, you could try cleaning it up with the appropriate tap and the use thread locker since there can’t be too many threads in a thin piece like that.
  • shortfall
    shortfall Posts: 3,288
    :) F
    Alejandrosdog wrote:
    Is the thread totally stripped or just damaged?

    If damaged, you could try cleaning it up with the appropriate tap and the use thread locker since there can’t be too many threads in a thin piece like that.

    The thread appears ok to the naked eye and bizarrely I only noticed the problem after I had removed one of the bolts to get a match at my LBS for another bolt that had dropped out and gone missing at some point. When I came to screw it back in it just wouldn't nip up.
  • rafletcher
    rafletcher Posts: 1,235
    If it won't nip up then it's trashed - or you have the wrong bolt.
  • shortfall
    shortfall Posts: 3,288
    rafletcher wrote:
    If it won't nip up then it's trashed - or you have the wrong bolt.

    It's definitely the right bolt cos it came out of the same chainring. Suspect you're right about it being trashed though but I threadlocked this afternoon. Will report back after the weekend when I've had chance to ride it.
  • monkimark
    monkimark Posts: 1,884
    Is it thick enough to use a helicoil?
  • shortfall
    shortfall Posts: 3,288
    monkimark wrote:
    Is it thick enough to use a helicoil?

    Not sure but if fitting a helicoil involves drilling the old thread out then probably not as the holes are right at the outer edge of the chainring. I've got an old Centaur chainset where the securing bolts screw into a threaded nut/sleeve that slides in from the other side and I considered drilling the holes to accept one of these but discounted the idea due to their being insufficient metal.
  • keef66
    keef66 Posts: 13,123
    Must admit it sounds a bit flimsy cutting a thread in something as soft and thin as an alloy chainring. Or is it beefed up at those points?

    I suppose from an engineering POV despite their eye-watering cost the rings are viewed as wear parts, so they probably don't build them to withstand frequent dismantly / reassembly...
  • shortfall
    shortfall Posts: 3,288
    keef66 wrote:
    Must admit it sounds a bit flimsy cutting a thread in something as soft and thin as an alloy chainring. Or is it beefed up at those points?

    I suppose from an engineering POV despite their eye-watering cost the rings are viewed as wear parts, so they probably don't build them to withstand frequent dismantly / reassembly...

    If the threadlock doesn't work I might try drilling it to accept the 2 piece older Centaur solution just to see what it looks like on the basis that I'll have to get a replacement anyway.
  • shortfall
    shortfall Posts: 3,288
    So I put some threadlock on and left it a couple of days before riding. Had a couple of short rides over the weekend and so far it's held in place. I guess only time will tell if it's a long term solution.
  • shortfall
    shortfall Posts: 3,288
    Update.
    Several hundred miles later it's still holding. Hopefully the loctite bodge has worked.
  • keef66
    keef66 Posts: 13,123
    Excellent news!
  • shortfall
    shortfall Posts: 3,288
    edited June 2019
    Update part deux.

    So inevitably the bodge failed and the substitute bolt dropped out after a hard hilly ride. I decided to have a go at drilling out the damaged thread and doing a more permanent repair. I have an old Daytona chainset and I was able to drill out the old hole and fit the recessed sleeved nut from this to accept the bolt from the other side.

    6zy4g9.jpg

    20kuamh.jpg

    The finished article isn't pretty but it works and should be a lasting repair.

    f0b6fl.jpg
  • keef66
    keef66 Posts: 13,123
    Top work that man!

    I think the inner ring on the Daytona looks like it's seen a long and active life!
  • shortfall
    shortfall Posts: 3,288
    It belonged to my neighbour who gave me a load of odds and sods when he cleared his garage out. It looks like he got full use out of it!
  • pinno
    pinno Posts: 52,097
    Yes, the problem with Cyanoacrylate is that it's brittle and susceptible to all the vibrations and potholes a bike will experience.
    Good fix.
    I have a half dozen of those chainring bolts - happy to donate them for the next fix.
    seanoconn - gruagach craic!
  • amrushton
    amrushton Posts: 1,307
    The chainrings aren't threaded, the threads are on the bolt and the securing nut (slotted piece). If you have the hidden bolt Campag (2nd pic), the actual arm acts as the nut as the receiver is inset and the bolt screws into the arm. That chainring has to go - that's a serious amount of wear.
    Miche/Stronglight/TA do compatible rings. In CT format it's 110bcd but that offset bolt means the ring has to be campag specific
  • shortfall
    shortfall Posts: 3,288
    amrushton wrote:
    The chainrings aren't threaded, the threads are on the bolt and the securing nut (slotted piece). If you have the hidden bolt Campag (2nd pic), the actual arm acts as the nut as the receiver is inset and the bolt screws into the arm. That chainring has to go - that's a serious amount of wear.
    Miche/Stronglight/TA do compatible rings. In CT format it's 110bcd but that offset bolt means the ring has to be campag specific

    It's the inner chainring of the Record chainset that was damaged. One of the threads was damaged when I was removing it which was bizarre as that usually happens if you over tighten something. The knackered Daytona chainset was only used for donor parts as the chainring bolts can be used in place of the ridiculously expensive Record items. In this particular instance I drilled the damaged thread out of the Record chainring so it would accept the sleeved securing nut and I secured it with one of the bolts from the Daytona. It cost me nothing to do this and saved me probably £100 or more if I'd replaced the chainring with a Record replacement and had to buy an entire set of bolts (which don't come supplied as far as I can make out). The only slight downside is that the Daytona bolts are chromed allen headed and the Record ones are black torx heads. You wouldn't know unless you were looking. Read the thread from the beginning and it should become clear.
  • pinno
    pinno Posts: 52,097
    On that particular Record chainset, is the chainring itself threaded?
    seanoconn - gruagach craic!
  • shortfall
    shortfall Posts: 3,288
    Pinno wrote:
    On that particular Record chainset, is the chainring itself threaded?

    Yes. One of the holes on the inner chainring lost its thread during removal. I tried a bodge with a Daytona bolt and some loctite threadlock which only lasted a few hundred miles so I drilled out the damaged hole so it was big enough to accept a Daytona sleeved nut and then screwed it together with the relevant Daytona chainring bolt. Genuine Campag bolts are about 35 quid for the set. You might be able to get them individually from your LBS spares bin but as the Daytona ones are the same I've previously used one of these. From reading it seems as though I'm not alone with the bolts coming loose although it's taken about 5 years to start happening to mine.
  • Alejandrosdog
    Alejandrosdog Posts: 1,975
    Proper job!
  • pinno
    pinno Posts: 52,097
    Shortfall wrote:
    Pinno wrote:
    On that particular Record chainset, is the chainring itself threaded?
    Yes.

    That's all I needed. :wink:
    seanoconn - gruagach craic!

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