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To prevent future punctures or keep delaying them, can I use super glue for this purpose? What can I do?

I do a lot of street riding and am concerned with small glass shards ruining my rides. I had a pinched tube destroy my bike tyre when it exploded. I am already making use of an old bike tyre inside my current tyre as a precaution.

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    Super glue is probably not the best choice. I suppose it would harden out and just fall out of the cuts.
    – DoNuT
    Commented Jul 26, 2023 at 7:47
  • Perhaps check bicycles.stackexchange.com/questions/89735/… for some tips.
    – DoNuT
    Commented Jul 26, 2023 at 7:50
  • Welcome to the site - I'm not sure how your pinched tube destroyed the bike tyre by exploding - a pinch flat is too-low pressure and allows the rim to press through the tube-tyre into the road-surface. Too-little air pressure can also cause the tyre to flex and fail faster because of the flexing. Can you use edit to expand on that? I suspect the pinched tube is unrelated to the glass question, other than both being in tyres.
    – Criggie
    Commented Jul 26, 2023 at 8:34
  • Instead of regular super glue try flexible super glue.
    – sjakobi
    Commented Aug 16, 2023 at 16:52

5 Answers 5

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Against glass on roads, there are three measures (pick one or two ;)), and mostly preventive:

  • Puncture Resistant Tires: there are product ranges meant provide additional protection (typically kevlar reinforcement, and a buffer layer between the exterior layer of the tire and the part in contact with the tire). These tires have as main inconvenient to be heavy and rigid, which means you have to run them at higher pressure for efficiency. The most known ranges are Schwalbe Marathon and Continental Contact (tip: if you live in a city with shared e-bikes, look at what they have).
  • Tubeless Tires: require tubeless tires & compatible rims. The tire is mounted directly on the rim, without inner tube. Then you put a sealant inside, that is a liquid that will clog the holes. This system works well with small punctures (<3mm — small ones will be clogged by the liquid without intervention, larger one will require some repair, that can be done without removing the wheel), requires regular topping off of liquid sealant (twice per year for example - the exact rate depends on a bunch of factors: temperature, kind of sealant, permeability and volume of the tires,...) and allows to run the tires at lower pressure, which is good for comfort. For urban use however, the choice of tubeless tires is limited, as this technology has been originally designed for off-road bikes. But there are some examples: Schwalbe Marathon Allmotion, some Schwalbe G-Ones,...
  • Tire Inserts (Tannus Armour for example): special foam fitted inside the tire that is meant to prevent damage on the rim in case of puncture, but can also act as buffer for some kind of perforation. Makes mostly sense for tubeless or non-puncture resistant tires.

Superglue is a strange choice for me: you need to locate the shard to apply the glue, and in that case better to remove it — the outer layer of a tire can be damaged and has no structural role. A tire inside the tire might help for some perforating damage, but if the two tires are not puncture resistant, I would suspect that it will be less effective than a proper puncture resistant tires.

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    I assumed they were taking out the glass then trying to glue the remaining cut shut.
    – Chris H
    Commented Jul 26, 2023 at 8:19
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    Footnote: Puncture protection exists on a continuum, with Marathon Plus being the toughest (in Schwalbe's range, which I'll use as an example). Marathon Mondial and Marathon GreenGuard aren't far behind. Marathon Supreme is the sweet spot for me as a long-distance tyre - supple sidewalls for easier rolling, but still quite a lot of protection under the tread. And that's just (some of) the Marathon range, before you get to the less-protected tyres
    – Chris H
    Commented Jul 26, 2023 at 8:23
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    @ChrisH (1st comment): indeed, that's why I mentioned that the outer part of the tire can take damage.
    – Rеnаud
    Commented Jul 26, 2023 at 9:10
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    Minorest of nits: I think it'd be better to say that sealant needs to be topped off "when it gets low", not twice year. Sealant consumption rates depend on too many factors to be so prescriptive, IMO.
    – Paul H
    Commented Jul 27, 2023 at 18:52
  • @PaulH I don't disagree with you, the issue is to know "when it gets low". It would deserve a dedicated question... (text edited to clarify this point). The reasoning being that a reasonable excess of sealant is better than to little.
    – Rеnаud
    Commented Jul 28, 2023 at 14:24
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With some kind of protection inside the tyre, the best you can do is check the tyre occasionally. The tyre doesn't have to be airtight (assuming you're not running a tubeless setup, and it sounds like you're not) because it's the tube that holds the air. So a tiny hole through the tyre doesn't matter in itself. When I fixed a puncture yesterday I picked out 5 shards of glass; only one had penetrated.

However you can improve a couple of things in your setup even without going to the expense of tougher tyres:

  • Rather than an old tyre, there are thick polyurethane liners (the big brand is Mr Tuffy, but there are cheap imitations). These do a good job of stopping things that have made it through the tyre, before they reach the tube. I've been trying a thinner liner as well, but so far haven't reached any conclusions.
  • There are sealant-loaded tubes. Personally, I'm not keen, as the sealant doesn't last forever, but these should seal pinpricks. If the shard is still there, it will pierce the tube again.
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For a moderate hole/cut in the tire, I would patch the inside of the tire because the cut can expand over time. The patch will arrest this some.

Patching the inside of a tire is fairly straightforward. With the tire removed, locate the cut/hole. Clean the area where the patch will be applied. Use isopropyl (rubbing) alcohol on a clean cloth. Avoid using the sandpaper to roughen up the inner tire surface if the cords of the tire are close to the surface as weakening/tearing them will not be good for the tire. If the patched surface is clean, the patch should still adhere. Then proceed with patching normally (apply vulcanizing cement, allow to dry, apply a suitably-sized tire patch, and press the patch firmly to gain a good bond from edge-to-edge of the patch)

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    The question is asking about cuts in a tyre, not in a tube. I don't know anyone who patches tyres on a bike; you should describe this process.
    – DavidW
    Commented Jul 26, 2023 at 16:36
  • Welcome to the site - Do you mean booting the tyre with a patch on the inside ?
    – Criggie
    Commented Jul 26, 2023 at 19:31
  • I have used this process successfully before on a relatively new tubeless road tire that was salvageable and I preferred not to trash. It can work pretty well keeping a cut from spreading. Sometimes I have done this in tandem super glue fusing on the outside of the cut.
    – Ted Hohl
    Commented Jul 27, 2023 at 15:23
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If the cut is small, and you've removed whatever sharp make the cut, then just leave it.

Any cut under 1-2 millimetres should be fine to leave, as long as

  • cut does not show any threads
  • tube is not visible at any time even when inflated.

If your cut is more of a hole (ie, with width) rather than a slash, then reconsider, but for a small gash I'd just keep riding.

You've already "booted" the inside by adding a second layer with the extra inner tube, but its also possible to put a patch on the inside of the tube for additional reinforcement.

However, also remember that tyres are consumables so replacement might be the best long term solution. Also, try to either avoid areas where you know there is a lot of broken glass, or report it to the local authority (council etc) for cleanup.

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    Avoidance is often recommended, but if you need to be in the city centre, you need to be in the city centre, and debris accumulates where bikes often end up. This end of my commute I could report new broken glass daily (and get nowhere by doing so)
    – Chris H
    Commented Jul 26, 2023 at 8:40
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I have used superglue with some success on cuts in a tire. If a cut is small and not very deep I ignore it. If the cut is larger, but not too large, the superglue method can have some success. I have only done this with tubeless road tires, and only when the tire is not very worn so as to get a few more miles out of a tire before having to replace it (lowering the cost per mile/km essentially).

The process to use for this is to locate the cut and make sure it is clean so the superglue will adhere and without any remnants of glass in it. Next, lower the air pressure in the tire to about 20-25 psi (I normally ride at about 80 psi on a 28mm wide tire). Lowering the tire pressure will allow the spread of the cut to reduce to where the cut closes up with the sides of the cut contacting each other instead of spread open. Leaving some pressure in the tire is a convenience when running tubeless as one can easily add air when done and not have to reseat the tire bead. If one is running tubes, the tire pressure can be dropped lower, even to zero if desired.

Once the tire pressure is reduced, position the cut at the top of the wheel (so the superglue will not run down the tire). Then squeeze/flex the tire at the cut to open the cut and then create a small pool of superglue in the cut opening. Stop squeezing the tire and excess superglue will be pressed out of the cut. Wipe the excess with a paper towel or a clean rag, and allow the superglue some time to cure before reinflating the tire.

In my experience, the "repair" will last for many miles, extending the life of the tire. Occasionally, the repair will open up partially or fully after some time. There will likely be a thin remnant of superglue that remains on the outside of the tire that surprisingly takes many miles to wear off.

This experience is on a road tire, at 80 psi, on tarmac. Rougher/off-road conditions, different tire pressures, increased tire flexing may make a superglue repair less durable. Fortunately, it is easy to try without much cost involved, so it is worth a try if the tire condition is not too bad and worth saving. If it does not work for a situation, then not much has been lost.

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