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I've got a relatively new bike tire (hard case Bontrager) that got punctured by a nail. So now the tube bulges out of the tire and is of great risk of bursting (though I biked several miles before realizing this).

I'm wondering if it is possible to patch the tire? If so, how would you do this?

I'm guessing you'd want a non-stretchable patch.

  • You can sew it with dental floss. – Klaster_1 Mar 13 at 3:21
  • Do you run tubeless or tubed ? – Criggie Mar 13 at 6:16
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now the tube bulges out of the tire

It's likely time to get another new tire - this one is probably dead.

The tube bulging out of the tire means that the structural integrity of your tire is compromised - one of the functions a tire must do for you to ride safely is hold the tube securely. This tire no longer does that.

And a patch really can't fix it. The fibers embedded in the rubber compound are likely cut. It's those fibers that give the tire the strength it needs to hold the tube in place against the pressure of the air inside the tube, and no patch can uncut those fibers. A glued-on patch can fail, as the glue is not really designed to take the shearing forces that are pulling the tire apart at the cut. The tire's fibers are designed to withstand those forces, but they're cut.

If you do the math, the total forces put on the rim and tire by the air inside the tube are pretty substantial. For example, a 1.5" 29er tire has an area over 410 square inches (area of a torus). If that tire is inflated to mere 50 psi, that's a total of over 20,000 lb of force spread out over the area of the tire trying to pull it apart and push it off the rim.

A tire boot (as mentioned in what's currently the other answer) is, IMO, a temporary fix for a cut tire. It gets you home.

Tires are wear items - they wear out, sometimes faster than you'd like.

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To get you home, you can use a tyre boot. This is essentially a non stretchy patch that sticks on the inside of the tyre. They're not recommended for long term use but people do run them long term (for example relegating them to a commuting bike/wheelset). If you do use them long term it's a good idea to check then occasionally. This assumes tubed tyres.

Boots also don't work next to the bead as there isn't enough material for them to stick to and resist the considerable load.

I've improvised a boot from a glueless patch (and run the tyre soft). Crisp (chips) packets, gel wrappers and strong banknotes are also used. Something sticky to hold it in place while you reassemble and inflate is a good idea.

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    A once-popular option was to take a US dollar bill (quite robust material) and fold it a couple of times, then slip it between tire and tube. A properly installed boot of decent material should be good for hundreds if not thousands of miles, the main problem being that it's apt to get displaced on a subsequent repairs. – Daniel R Hicks Mar 13 at 12:06
  • @DanielRHicks I do have a few US notes, and our new polymer notes are tough as anything. I lead with calling a boot a get-you-home repair mainly because the manufacturers say that on the grounds of safety; my own personal experience is insufficient. – Chris H Mar 13 at 13:49
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    A gel wrapper works nicely and because of the content it is sticky. So you don't need some tape or else to keep it in place when inflating the tyre. Speaking from experience! – Carel Mar 13 at 15:59
  • @Carel I didn't realise it was that sticky! (and I have a little duct tape with me anyway) – Chris H Mar 13 at 17:31
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    I managed to make a decent boot out of a piece of an old inner tube glued in place with vulcanizing solution from a patch kit, with a bit of vulcanizing solution inside the tube to keep it flat. – HAEM Mar 15 at 10:02
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Personal experience.

I've successfully patched a round tread-hole of ~1mm across where the tube herniated through and wore through after ~200 km. Buff then tube patch on the inside, and a spot of RTV to fill the void on the outside.

This was a hole not a cut, so the integrity of the tyre carcass was fine.

I figured a patch added no more offset weight than the same patch flipped and stuck on the tube.

Probably okay for commuting and normal usage, to get the maximum wear out of a tyre. Not suitable for a race.

  • What is RTV? My hole is small, but probably more like 2-4 mm. – Aaron Kreider Mar 14 at 20:51
  • @AaronKreider RTV is a silicon sealant that sets at room temperature. Essentially its something to fill the small void where tread is missing. 4mm is getting rather big, my hole was about 1mm across. – Criggie Mar 14 at 20:54
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I did use a tube patch on a sidewall hole in the tire (I too had a nail) - and the tire bulging has decreased somewhat. It's not a long term solution though.
If the hole is not on the sidewall but on the tread, you might possibly solve it with an auto tire patch (the kind used for holes in the tread).
Keep in mind that auto tire patch (the one in the thread) is NOT TO BE USED for sidewall holes (once a car tire has a sidewall hole, you must buy a new one).

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You could have used a sleeve glued on the inside using vulcanising fluid, you can do this in any position on the inside of the tyre. You just use a oversize patch vulcanized in place, works as well as anything and is safe as it holds the tyre together where it is split.

  • This is also my experience. – jaknudsen Mar 20 at 12:35

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