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Inner tube patching question

Old 10-12-22, 09:07 PM
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gululok
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Inner tube patching question

I just got my first leak. Not from a puncture, just general wear and tear. I did get a patch kit for this, but with the hole so close to the valve, I'm wondering if the valve stem cause any complications. Would I damage the valve if I apply a patch so close?

Also, since the tube leaked with no puncture, is it time to retire this tube? If I patch it, would it be good as new, or would it be the first of many leaks because the tube is just too worn down.

Also also, what do I do with old tires/tubes? Do bike shops recycle them, or straight in the garbage? Is there any reason to keep old tires/tubes around?


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Old 10-12-22, 09:27 PM
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I consider a flat like yours to be UNrepairable. Not because you can't patch that close to the valve, but because the likely cause will repeat very soon at the edge of the patch.

I'll venture that you have fairly narrow rims. If so try to visualize the following as you read. Picture your tire and rim in cross section. The tire assumes the shape of an Ω (omega). The tube fills the space above and forms a circle, spanning the gap between the beads sitting in your rim. However, there's space below the beads, and under pressure the tube balloons down to fill the rim.

Friction prevents the tube from sliding around, so the narrow section spanning thee gap blows down getting stretched like crazy. The problem is worse near the valve because the reinforced section doesn't blow into the gap, so the tube right there ends up stretching even more, causing tears like yours.

Sometimes this happens fairly soon, but often the tube survives until it's a bit older and has lost some stretch. You can patch it, but you can't restore it's youth. So, it's time for a new tube.

Note---- when installing do this last step before inflating to pressure. Push the valve down into the tire to make sure nothing is trapped under the bead. Next pull the valve back out, gently but firmly to be sure the base is back below the beads so the tube doesn't have to stretch down there.
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Old 10-12-22, 10:14 PM
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Originally Posted by FBinNY View Post
I consider a flat like yours to be UNrepairable. Not because you can't patch that close to the valve, but because the likely cause will repeat very soon at the edge of the patch.

I'll venture that you have fairly narrow rims. If so try to visualize the following as you read. Picture your tire and rim in cross section. The tire assumes the shape of an Ω (omega). The tube fills the space above and forms a circle, spanning the gap between the beads sitting in your rim. However, there's space below the beads, and under pressure the tube balloons down to fill the rim.

Friction prevents the tube from sliding around, so the narrow section spanning thee gap blows down getting stretched like crazy. The problem is worse near the valve because the reinforced section doesn't blow into the gap, so the tube right there ends up stretching even more, causing tears like yours.

Sometimes this happens fairly soon, but often the tube survives until it's a bit older and has lost some stretch. You can patch it, but you can't restore it's youth. So, it's time for a new tube.

Note---- when installing do this last step before inflating to pressure. Push the valve down into the tire to make sure nothing is trapped under the bead. Next pull the valve back out, gently but firmly to be sure the base is back below the beads so the tube doesn't have to stretch down there.
Interesting.

My rims are not super narrow, I don't think (26"x1.95 tire on Weimann ZAC1900 rim), but I see what you mean.
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Old 10-12-22, 10:38 PM
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Agree with FBinNY, patching in that area would have a low chance of success. Replace the tube
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Old 10-12-22, 11:03 PM
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I've been able to successfully patch holes that close to the valve - it's just a lot more work as you have to sand down all those ridges smooth without tearing another hole - a Dremel with a barrel sanding tip is a huge time-saver. And the success probabilities aren't always 100%. But I concur that unless the underlying issue causing the excess tube expansion into the valve area isn't addressed, the flats will recur, whether with a patched or new tube. Some people build up under the rim strip with silicone or electrical tape into a wedge on each side of the valve hole, but be careful not to put anything near the bead or you greatly increase the risk of blowout due to a poorly-seated tire bead.
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Old 10-13-22, 06:29 AM
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I'm curious what caused that flat. Was the bike left sitting for a long time until there was no air left in the tire, then wheeled around a bit so something sharp could get between the valve and the rim before the tire was re-inflated?
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Old 10-13-22, 06:39 AM
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I have had a number of flats with this issue. I attributed it to poor quality tubes. No patch ever worked for me so the $7-8 is wasted. I think I received a batch of bad ones, Continentals.
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Old 10-14-22, 11:36 AM
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Originally Posted by gululok View Post
I just got my first leak. Not from a puncture, just general wear and tear. I did get a patch kit for this, but with the hole so close to the valve, I'm wondering if the valve stem cause any complications. Would I damage the valve if I apply a patch so close?

Also, since the tube leaked with no puncture, is it time to retire this tube? If I patch it, would it be good as new, or would it be the first of many leaks because the tube is just too worn down.

Also also, what do I do with old tires/tubes? Do bike shops recycle them, or straight in the garbage? Is there any reason to keep old tires/tubes around?
I'd try to patch it only in the field to get home.

Time is money, ​​​​​​it's not worth my time to repair this kind of damage otherwise. YMMV.
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Old 10-14-22, 12:17 PM
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Originally Posted by alexk_il View Post
Time is money, ​​​​​​it's not worth my time to repair this kind of damage otherwise. YMMV.
Time can indeed be money, but it can depend on context.

I patch tubes by the dozens in weekly batches for two nonprofits (Rusty Spoke and Recycle your Bicycle). I charge (and get) hundreds of dollars an hour for my professional consulting time, but tube-patching time is where I unwind, sit in the back yard, put on a little music, have my drinkables and water bucket handy (and try not to confuse the two), pop the cap on the cement and rev up the ol' Dremel, and start hole-locating, marking, prepping, and patching on an assembly-line basis, using genuine Rema cement and patches. I find it a good way to unwind after a busy day of work, and I can knock out about 20 tubes in an evening and not feel rushed about it. If a tube has up to two detectable holes, I'll mark and patch it, but 3 or more and it goes on the "recycle / toss" pile. The biggest de-stressor and time-saver is the Dremel and sanding drum - it takes the most important and often most frustrating step in patching and makes it a simple task done in just a few seconds. And with the price of new tubes these days, it saves these organizations up to hundreds of dollars in tube purchasing costs for just one quiet evening's work.

Unless the patch doesn't hold, or you find two slow pinhole leaks when you test the tube you just patched. Then it's not relaxing, and can result in me getting in touch with my inner muleskinner. But fortunately this seems to be considerably less than 5% of the total.
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Old 10-14-22, 01:21 PM
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Originally Posted by RCMoeur View Post
Time can indeed be money, but it can depend on context.
I marked the context with bold, see below. Hope it helps to make it more clear.

Originally Posted by alexk_il View Post
I'd try to patch it only in the field to get home.

Time is money, ​​​​​​it's not worth my time to repair this kind of damage otherwise. YMMV.
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Old 10-14-22, 01:42 PM
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Originally Posted by FBinNY View Post
...

Note---- when installing do this last step before inflating to pressure. Push the valve down into the tire to make sure nothing is trapped under the bead. Next pull the valve back out, gently but firmly to be sure the base is back below the beads so the tube doesn't have to stretch down there.

Thanks again FB, some of us had to learn and then relearn this trick the hard way...
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