This is a basic tire repair question. Apologies if it's been answered before.

So I got a glass piece through my Schwalbe Kojak tire.

I removed the glass, checked for anything left behind, cleaned out the tire and put in a new inner tube.

But the new tube popped on first inflation.

I checked again. It looks as though the puncture left behind is sort of protruding inwards. It could've caused the tube to rip.

I could try trimming the bits down but I'm not sure how effective this would be.

Should I cover it up instead with some sort of tape?

Any advice is much appreciated.

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If you think that is causing the problem, put a patch on it.
You may as well put a patch on the old tube and save it.

Was the new puncture in the same place? To my eye, I can't see that cut causing a second flat, but a photo is different than having the tire in your hands. If in doubt, put a pice of duck tape over it, applying id on the bias so it's weave follows the tires bias weave angle.

BTW- odds are you punctured the new tube with a poor install, either pinching it, or trapping it under the tire bead.

I always probe holes with the leather punch of my Swiss army knife to feel for bits of glass left behind.

What size of tire is that, and how big of a hole did you have going through the tire? If you have a 1/4" gash 100% through the tire, then you really need some kind of a boot to keep the tube from protruding out the hole (which could cause it to pop quickly).

I ran half the winter on a 25mm Marathon tire with a deep gash, but only small point hole through the inner casing. I ran a week or so without a boot, then tried a Park boot which is meant to be temporary. It was too big and caused the tire to thump, so I cut the boot it in half and put it back in. I don't know, maybe 500 miles before I decided to switch bikes. The Park boot does have pretty square edges, but seems to be ok so far.

Some people have suggested that maybe a Radial Tire patch has the strength to act as a small boot, and might be better than the Park boots. I haven't tried it yet, but it is worth considering.

Ok let's try that again

I'll try the duct tape method.

I was careful to make sure that there was no pinching. But I suppose there can be no shortage of being careful.

This is a 20" 406 tyre - 1.35" I believe. Fairly good condition generally.

The gash is about 7mm long. But since it's right through the kevlar bit, I think perhaps the region is tough. A boot may not be necessary.

There is still a piece of glass in there.

I have had this problem when there was a piece of glass that did the initial flat and a shard or two that was in the tire and worked it's way out after rolling a few feet. I now examine very carefully and would vote for a $5 deposit on all bottles.

If inflation pressure is high enough, a 7mm gash will allow the inner tube to push through. A hole in the middle of the tread like that is bad because even though the inner tube may not blow right away, the rubber of the inner tube can contact the road and wear through. You absolutely would need a tire boot

That's my impression too. I'd push some kind of poker in, from the outside, and see what can be cleaned out of the hole. Also, I'd carefully inspect the entire rest of the tire for more glass.

That would seem to indicate an installation fault.

If you can see the blue from the inside for the 7mm, that means that it is a full thickness cut that entire length. You can watch that hole when you inflate the next tube, but I'd just go ahead with the boot.

The boot will also help prevent future debris from working down to your tube.

Pressure and tube thickness may also make a difference. The kid's bike tires can be quite forgiving. A high pressure road time on a quality folding bike may be less forgiving.

Here is a photo of the damaged tube. My initial impression, given the direction of tear, was that the expanding tube caught on to that protruding bit from the tire, and just ripped when it stretched too much.



I've done this but could not see anything come out. Perhaps it's stuck in there.

I'll go with the boot idea. It should solve all the possibilities I think - any tiny glass bits inside the cut would not be able to penetrate as it would provide some sort of protection, and it would shield that protruding bit from the tube.

That looks like a cut from something sharp, not a blow through. I'd investigate the old hole and the rest of the tire for something sharp causing it.

Well seeing how much of a mystery it is, you should patch up the old tube and clean out the entire wheel. Whenever I get a second flat in the same ride I run my fingers gently over the tire to check for any existing debris. Usually I find something. Other times i find that I was the one that messed up by pinching it. Do a fresh install and see if that solves your problem. Maybe you pinched the tube with the tire.

+1 on probing the hole with a large needle or something similar to make sure there is no glass left behind, and for checking the rest of the tire as if you rolled through some glass, there is the possibility of another less obvious puncture somewhere else.

I keep a metalic Sharpie marker around and mark the direction of rotation on my innertubes and, when I get a puncture, to mark the leak so that I can line up the valve stem to find the correct location to check on the tire. This is another good reason to install tires with a reference point (either the label or the max inflation info) adjacent to the stem hole in the rim.

For small tears like this, I use the regular Park innertube patches as a boot. Just clean the inside of the tire well with a little alcohol, let dry and apply the patch per directions. Don't count on any boot to keep even a small shard of glass from eventually working it's way back through. Every time your wheel goes around that shard gets tapped a little deeper. This is why you need to inspect your tires any time you ride through glass, even if you don't get an immediate flat. Even a small bit stuck to the surface can eventually be driven through to cause a flat miles later. Many mysterious recurring flats can be traced to not properly inspecting the tire and removing and foreign objects found, no matter how small. If there is any gap in the outer surface of the tire from the puncture, a dab of Shoe Goo or similar product will keep out new debris.

It would be interesting to see the shape of the cut on the outside of the tire. The problem with a cut across the tread like that is that the opening in the tread will constantly be opening and closing with each wheel rotation as that part of the tread comes into contact with the ground. This will tend to pick up any debris that it comes into contact with. Stuff will get pushed into the tire carcass. Anything sharp could eventually pierce through. Duct tape isn't resistant enough, you need a tire boot that is very puncture resistant. Think about how easy it is to tear off a piece of duct tape when you are using it. That and the adhesive on the tape would tend to make anything that pokes into the hole stay there

Whatever theory you form has to match the facts.

The theory that the second tube failure was caused by the tire cut doesn't.

First of all, small cuts like the one in the OP's tire don't cause larger cuts in the tube, and even if they did, the orientation is wrong. The cut in the tire is angled almost crosswise to the tire, while the tube is cut almost lengthwise. It would have been informative if the OP had made a reference mark in the tire at the valve, because that would have told him if it was in the dame place.

Looking at the tube, and given the timing, I suspect that the second tube flatted from an installation error. It might have been cut by a tire lever edge (if levers were used), or been trapped under the bead and torn on inflation or soon after.

To the OP, many here carefully mount tires so the label is at the valve. I don't but I do make a mark where the valve is before removing the tire. Either way allows you o line up the tube against the tire aand know where on the tire to look for the cause of a puncture.

+1


That looks like the tube got pinched during installation

"Here is a photo of the damaged tube. My initial impression, given the direction of tear, was that the expanding tube caught on to that protruding bit from the tire, and just ripped when it stretched too much."

Tubes don't stretch much when you pump them up inside the tire, there is very little room for them to expand.

I also suspect that it was pinched or torn on installation. Done it many times myself. It's a learning process.

The hole in the tube looks more like a blowout caused by improper installation. It is possible for the same thing to happen from a large cut in the tire - generally much larger than the one shown. With 'medium' sized cuts in tires, you might start to see the tube bulging through, but usually not enough to pop. It if did pop due to that cut, it would have bulged out like a kid blowing a bubblegum bubble before popping.
When a tube is improperly installed in such a way that it is trapped between the tire and rim, usually the tube pushes the bead of the tire off the rim then immediately blows up with a loud POW.

toss the tire and move on

Thanks for the comment.

Unfortunately I had not marked the valve location on my tire. It's a good idea. I shall do it in future.

I did not use levers during installation.

After inserting the tube I inflated it slightly and I checked along the length if any part of the tube had gotten stuck on to the rim. In this way: https://youtu.be/-XUFVrl0UT4?t=5m6s. Should I have done any other check?

It is precisely because the orientation between the tube damage and tire cut is perpendicular to each other that I feel that the former was caused by the latter.

When I run my fingers on the inside of the tire they catch on to that bit. It sort of sticks out. This is why I assumed the inner tube had got caught on to it and ripped in the way it has while inflating.