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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 05-15-12, 04:22 PM   #1
GEOlson
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flat tire under a spoke

Today I got a second flat tire in two weeks and I think it's from the same spot. There's nothing in the tire and the puncture in the tube on in the inside of the tube. It's right in an indentation in the rim tape where a spoke is. The tape is still in tact but the dip felt slightly deeper that the rest. There is also no part of the spoke pushing through the tape. Is this simply resolved by replacing the rim tape? I still have the original tape (2005 model year, ~2300 miles on the bike), and it is the quality canvas-like material, not the thin rubber.

The funny part is, I was talking to my coworker about how to fix a flat because he was telling me about his recurring flat, when after about 5 minutes of talking, standing next to my bike (at work, in an office) and the tire decided to speak up with a PSSSSHHHHHHHHTTTT!
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Old 05-15-12, 04:33 PM   #2
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It really depends on the puncture on the tube. If the puncture is a small, approx. round hole, then you have something sticking out and poking the tube. From you seem to be suggesting about a "dip," I'd hazard a guess you have double wall rims. If so, and the tube looks like it's been cut along the side, then you may need to make sure the tape fully covers all the holes and then has at least a couple mm on each side so the tube has no chance of squeezing by the tape along the side. This may mean you need wider tape. Check the rim around that area for burrs too.
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Old 05-15-12, 04:56 PM   #3
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Wheels flex -especially if the spokes are not up to correct tension.

A spoke can poke through when you are riding with your weight on it but when the wheel is off the bike it looks just fine.
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Old 05-15-12, 04:59 PM   #4
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Thank you, guys. I will check spoke tension. It's a stock wheel on a Trek 1000, so it's an Alex Rim AT-450 road wheel. It looks like just a small slit, maybe 1-2 mm long.
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Old 05-16-12, 09:18 AM   #5
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Patching a patch?

I tried using a Park Tool pre-glued patch that failed after 20 minutes. I'm glad I changed it a little before I left work. Anyway, the tube was still in the garbage pail this morning so I decided I would wash it - that can doesn't get used a whole lot since it's not by the public entrance, and re-patch it. I used to adhesive remover to clean off the old glue, sanded it, alcohol swabbed it, and applied a new patch. I inflated the tube a bit, just enough to have a decent amount of pressure to test the patch. But I was wondering if rubber cement type patches can be removed and patched again?

I've never been good at patches, so is it the recommended way to smear the rubber cement on the tube and let it completely dry (for that type of patch)? I think I will go back to my German patches in the small green container.

And I pulled out my tube that was flat 2 week ago and it was in a different spot. A little further from the stem and on the outside of the tube, so I will inspect that tire for the cause.

Thanks for the advice!
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Old 05-16-12, 11:57 AM   #6
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Number one thing is to get the tube clean. All you need to do most of the time is to sand it unless it is so filthy that you are pulling more goop into the sanded area. Then most of the time all you need is to rinse it with water or use an alcohol wipe before sanding.

When sanding make sure if there is a rib or other imperfection that it is sanded down smooth.

That's all you need for a self-gluing patch. Just place it down and press for a few seconds. The tire or rim should keep it pressed against the tube until the glue really sets up over time. But it might fail if you ever swap tires. Self-gluing patches are temporary IMHO. I usually will peel them off and clean/sand and put on a real glued patch on when I get home.

With a glue patch you need to prep the tube the same way but the trick is not put too much glue on. Put it on and spread it out with the back of the tube so it is a consist and smooth coat but not too thick. LET IT DRY THOROUGHLY before attempting to lay the patch on it. It can take 4-5 minutes for the glue to dry. If you attempt to put the patch on before that your failure rate will be very high. Make sure not to touch or contaminate the back of the patch. Hold it with your fingernails at the very edge. Make sure you have it over the hole(s) and centered.

The area you have sanded/clean should be well over 2-times the size of the patch. The area you glue should be over 1.5 x the size of the patch. Don't put the glue on an area larger than the area you have cleaned or you will pull contaminants into the patch/glue and that will be were it fails.

After a day, if you have done the patch correctly the rubber will all be one piece. You won't be able to peel it off. It's just as strong (stronger because it is thicker) than the original tube.

Last edited by Amesja; 05-16-12 at 12:00 PM.
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Old 05-16-12, 12:21 PM   #7
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Thanks, Amesja! I will use your words of wisdom and experience and pass on the knowledge of fixing a flat. So far my tube hasn't leaked yet. But I will be sure to pick up a glue patch kit when I can, and alcohol swabs for cleaning. I figure the swan will make the tube dry, too, for the glue.
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Old 05-17-12, 05:13 AM   #8
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You should let the glue dry until it is "tacky" to touch - but not completely dry.

Here is an effective, albeit difficult, trick - taught to me at a mechanics course - which means you don't have to wait.

Splooge glue on patch and tube. Smooth each out to a thin even layer. Wipe your fingers clean! Using a cigarette lighter set fire to the glue on the tube. *Do not let the tube get hot and melt*. This means blow the burning glue out *immediately*. Now move to the patch, same thing. Then back to the tube. You keep going until there is no volatile solvent left - and the glue won't immediately and easily burn, 2 or 3 brief flames on each probably. See what I'm saying there - you shouldn't be holding the lighter next to the glue for more than a fraction of a second. Once it stops immediately popping into flame then it's ready to stick.

You are effectively quickly drawing all the solvent out of the glue without having to wait around.

Do not do this in a garden shed near petrol, do not do it inside the house near curtains, you probably should only do this in the middle of the Mojave desert. Or better still, not at all.

Seriously be careful. I can't say this enough. Have a bucket of water nearby to plunge burnt fingers in.

Once the glue is ready, stick patch to tube, quickly shake talcum powder on the patch and surrounds - clamp it flat while it dries.

If you survive then you will have the best patch you've ever done.

Do not reply with posts saying that you have accidentally torched your apartment building and hundreds of orphans have died.
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Old 05-17-12, 05:19 AM   #9
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Oh-pah!

Setting stuff on fire always helps any process...
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Old 05-17-12, 06:43 AM   #10
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Old 05-17-12, 11:03 AM   #11
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Quote:
Originally Posted by jolly_ross View Post
You should let the glue dry until it is "tacky" to touch - but not completely dry.

Here is an effective, albeit difficult, trick - taught to me at a mechanics course - which means you don't have to wait.

Splooge glue on patch and tube. Smooth each out to a thin even layer. Wipe your fingers clean! Using a cigarette lighter set fire to the glue on the tube. *Do not let the tube get hot and melt*. This means blow the burning glue out *immediately*. Now move to the patch, same thing. Then back to the tube. You keep going until there is no volatile solvent left - and the glue won't immediately and easily burn, 2 or 3 brief flames on each probably. See what I'm saying there - you shouldn't be holding the lighter next to the glue for more than a fraction of a second. Once it stops immediately popping into flame then it's ready to stick.

You are effectively quickly drawing all the solvent out of the glue without having to wait around.

Do not do this in a garden shed near petrol, do not do it inside the house near curtains, you probably should only do this in the middle of the Mojave desert. Or better still, not at all.

Seriously be careful. I can't say this enough. Have a bucket of water nearby to plunge burnt fingers in.

Once the glue is ready, stick patch to tube, quickly shake talcum powder on the patch and surrounds - clamp it flat while it dries.

If you survive then you will have the best patch you've ever done.

Do not reply with posts saying that you have accidentally torched your apartment building and hundreds of orphans have died.
Jolly, no offense but your advise is pretty much wacky; you're turning a simple process into a major safety issue. First, you need to let the glue completely dry, which will usually take no more than 4 minutes and usually much less. As you discussed, one needs to wait until all the solvent flashes off; the vulcanizing chemicals are suspended in the solvent. If the glue does not completely dry, than the solvent will prevent the vulcanizing process. It sounds to me your wrench misses the old days before they outlawed hot vulcanizing patches..
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Old 05-17-12, 04:30 PM   #12
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Well, I've done 36 miles since I put a new tube on and no flats, so I think it was just a fluke. The re-patch was still holding air today so I deflated it and packed it into my seat bag. I did "attempt" to true the wheel in case a spoke was loose. I say attempt because I'm an amateur with truing wheels, but all seems good so far.
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Old 05-17-12, 06:41 PM   #13
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Patching a patch?

Are tubes super expensive in the states? I reckon a patch kit is great for getting you home (much like the frame pump philosophy). But once your home - spend the $2 and put a new tube in.

In fact I ride with a spare tube in my saddle bag - along with a patch kit just in case I have a shocking run of luck...or happen to ride through a car accident involving a truck carrying thumb tacks...
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Old 05-17-12, 08:43 PM   #14
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I've got 3 tubes in boxes, but the last time I bought a Bontrager tube it cost $7. The patching a patch was removing the pre-glued patch that didn't make it, cleaning it up, and then reapplying a patch which so far has held air. I have a new tube in my seat bag as well as the patched tube, amongst all the other junk I can cram in there.
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