One of the rear rack holes on my aluminum frame have become stripped after a year of taking the rear rack off at least once a week. I've been using this bike for commuting and weekend riding, so I like to remove the rack when I'm not carrying panniers.

I've asked a few bike shops about rethreading the hole and have gotten multiple responses. One shop there is a tool that some shops have that can rethread it. Another said I was out of luck. One criticized me for taking the rack off often. The last one I asked said some shops could do it but you'd have to go up a screw size.

What's the consensus here on this type of frame repair? At the moment I can still use the rack since it's still secure with the one loose screw. I intend on getting a new bike at the end of the year for non-commuting, so I will make this a dedicated commuter bike where I can leave the rack on it when that happens.

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    Is it a pass-through hole? I mean, can you put a long bolt through and a nut on the back side to tighten it together? I would doubt the reliability of just trying to rethread the hole unless they're talking about making it slightly larger (originally M4 threads and rethreading to fit an M5 bolt). If there's enough material around the hole for that I would think it should be fine. – Noah Sutherland Jul 26 '17 at 23:38
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    Yeah, if it is possible I'd just get a longer bolt and a nut. If not probably rethreading to a larger size is the best fix. It's a simple job. For bigger, deeper threads you could use a Heli-coil type fix , but I doubt if it would work here. The most off-the-wall fix would be to get a frame guy to fill the hole with weld and redrill it. – Daniel R Hicks Jul 27 '17 at 1:49
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    I'd also suggest cutting threads for the next sized bolt or filling it and re-drilling it. And I also agree with the shop on removing and replacing the rack so frequently, especially if you were ogre-ish with rack installation -- you've got probably more an order of magnitude more uninstalls and installs than most bikes are expected to see. If you want to do the weekly install/remove, I'd use a rack like this, where the installation and removal hardware doesn't require screwing/unscrewing things from the frame every time. – Batman Jul 27 '17 at 3:02
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    Asking a clarification question - why are you routinely removing and refitting your rack? Are your panniers a non-removable part of the rack? Or is your rack oversized for its purpose? You should be able to leave the rack on the bike permanently and notice no significant differences - it shouldn't be over a kilo and lightweight alloy racks should be half that. If the weekend riding you do is compromised by a kilo of rack then you might longterm want a dedicated commuter bike with full fenders, and a dedicated weekend bike made of lightness. Comment cos not answer to question. – Criggie Jul 27 '17 at 7:19
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    @DanielRHicks just because it's not something you would do does not make it dumb. This is disrespectful of the OP. – Rider_X Jul 27 '17 at 18:52

A few ideas:

  • Buy a seatpost-mounted rack (this would be a good solution for the long term if you want to keep taking your rack on and off, but check the weight limits).

  • If you're going to keep doing this, when you've solved the immediate problem, put some stainless studs in the holes with threadlocker and use a nut on the outside. You should probably use a dome (acorn) nut to avoid hard edges.

  • If there's a rubbish thread but just enough to get a bite, degrease the hole, cover the first few turns of a stud in epoxy and screw it in. Leave overnight before fitting the rack.

  • P-clips onto the seat/chain stays can replace the mounting bosses for all but the heaviest racks.

  • You could probably tap it out. I'm used to M5 rack mounts so you'd need to go to M6. I'll the hole out with a 5mm drill then use an M6 tap. You'll probably need to start with a taper tap then change to a bottoming tap. You'll also need to open the hole on the rack to a little over 6mm (if you can't get a 6.2mm drill, use 1/4"). I reckon a metric tap set is worth having, but be sure to get one with pilot drills as these are otherwise uncommon sizes.

On my bikes I'd go for (1) P-clips (or tap if high loads and plenty of material); (2) tap it out (3) seatpost rack; (4) epoxy and only on my old bike. But I already have all the tools/materials for all these options.

All links are examples rather than recommendations.

It should probably go without saying but if you've got a child seat mounted on the rack, you should probably forget about the repair, or using the rack in its current state. But you can get a seat that fits to the seat post.

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    P clips are great - I made some roughly out of some light strips of steel (old computer L bracket slot covers) expecting to replace them in a year. They've survived 5 years and still work fine. – Criggie Jul 27 '17 at 7:21
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    I think the takeaway lesson here is "stop refitting the bolts" – Criggie Jul 27 '17 at 7:21
  • @Criggie your home made ones outlasted the ones I bought! But they're definitely worth having in the parts box. M5s should last ages if you're gentle even in Al but there might not be many turns – Chris H Jul 27 '17 at 7:26
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    The problem is steel on aluminium. Steel wins. Screwing and unscrewing a bolt so frequently will ruin the thread once more. – Carel Jul 27 '17 at 7:51
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    @Criggie I've never had any need to try them (I use anti-tamper torx stainless where possible for mounting accessories, and I'm not too concerned about weight) – Chris H Jul 27 '17 at 11:23

Most anchor points in aluminum frames are not an actual tapped holes in the frame. It is a threaded inset that attaches to the frame similar to the way a pop rivet works. On older frames they were sometimes referred to as braze-ons. If you search for Nutsert or rivet nut they may be available at your local home center. While the individual inserts are not expensive the insertion tool can be close to $80. The inserts can also be troublesome to remove. Attempting to drill them out usually results in the insert spinning in the mounting hole. A local custom frame builder may be able to help you as they likely have the tool to install bottle cage mounts and such.

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    Rivnuts can be installed using a single suitable bolt, and two ring spanners of the right sizes. You insert the fitting into the hole, then put a nut halfway onto the bolt,, then thread the exposed bolt thread into the rivnut. To compress it, you use one spanner to hold the bolt still, and use the other spanner on the nut and wind it down into the rivnut. This compresses the rivet part. Practice on scrap first! Threadlocker helps hold the rivnut too, once its been compressed. – Criggie Jul 28 '17 at 5:37
  • Rack and fender attachment points are almost never rivnuts. – Nathan Knutson Jul 28 '17 at 15:46

Going up a size (to M6) or installing a Helicoil are both good options if there's a reasonable amount of material surrounding the eyelet, which is true for all but the daintiest. If you want to keep taking it off regularly, the Helicoil is a little better option in terms of preventing similar issues in the future, since now you'll be doing it with steel threads. But either approach is sound and any real shop can do either as needed.

The simple, non-shop fix is use a longer bolt plus a nut. If clearance is tight, use a buttonhead M5 bolt run from the inside out, so the nut is outside.

  • For the heilcoil, would I use the same size as my current screw, or go up a size? The one on Amazon that pops up first looks to have reviews mentioning my exact issue, so I imagine this might be a good solution for me. – timgcarlson Jul 28 '17 at 4:55
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    Same as current, M5x.08 for almost all bikes. – Nathan Knutson Jul 28 '17 at 15:44

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