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Old 01-15-10, 12:33 AM   #1
markjenn
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Tube Patching Disappontments

Gentlemen, please explain what I'm doing wrong. I have been patching tubes for thirty years and am lucky to have maybe a 50% batting average with respect to a patched tube not slow leaking afterwards.

Checklist: I'm not stupid. I have a good patching kit (I typically use the Rema kit and patches.) I use fresh vulcanizing fluid. I follow directions, including roughing up the area, applying a thin layer of fluid, waiting five minutes, and then carefully pressing the patch down from the center out. But even when I do all these things, I often get slow leaks. And during the subsequent second attempt, I often note that the patch simply isn't sticking that well to the tube - it is pretty easy to pull it up from a corner. Shouldn't a properly-applied vulcanizing patch weld the patch to the rubber of the tube?

My theory is that there is often something on the tube which is preventing the fluid from working properly and from getting good adhesion. Would some alcohol wipes help? Would wiping down the tube with something a little more aggressive (e.g., lacquer thinner, MEK, acetone)?

I'm tired of messing with this to the point that I often just put in a new tube and throw the old away, even for the first puncture. But that seems like a waste.

- Mark
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Old 01-15-10, 12:55 AM   #2
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I've had a near 100% success rate. But when I was learning I found that any time I didn't get a total bond it was because I didn't abrade the tube enough. It isn't enough to just scuff it so it's got some scratches on it. I mean like dark and dull like you could fall into the hole you just created. No sign at all of the original tube surface finish should be left The rubber has to take on a chewed up dull look overall for a size that extends out to pretty close to the edges of the patches or just a hair beyond. There seems to be almost a skin on the tube that you have to cut away and expose the inner rubber before the patch will take well.

I've never used a solvent to clean the area. Just abraded it. I also tend to go with some 80 grit garnet sandpaper that I have aplenty thanks to my woodworking hobby. Using a fresh abrasion medium often may help. But I normally do a good half dozen at a time with the same scrap of sandpaper so contamination of whatever is on the rubber isn't an issue. But cutting off the surface "skin" surely is.

And when you press the patch into place after waiting until the glue has lost all its shine you want to pinch it down with a few seconds of all out white knuckle effort to achieve the best bond. But this second aspect won't mean diddly if the tube itself wasn't abraded well enough.

Hope that helps you to enjoy the near 100% success that I do.
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Old 01-15-10, 01:47 AM   #3
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Thanks for comments, yes, this makes sense.

I wonder if having a dremel handy in the shop might make the "abrading" step easier and more reliable. I try and do a good job with the little piece of sandpaper in the kit, but it is difficult to really get a nice uniform abrade across the entire surface of the patch. (In the field, I typically just use a new tube so as long as I don't get two flats in a ride, I don't worry much about field patching.)

Old-timers wil remember a kit called "Match Patch" in which you clamped a patch assembly onto the tube and then lit it on fire to fuse a patch onto the tube. You never worried about a patch leaking with these things!

- Mark

Last edited by markjenn; 01-15-10 at 01:53 AM.
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Old 01-15-10, 02:21 AM   #4
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I had this problem earlier and got sort of made fun of for not just throwing out the tube and starting afresh

However the super helpful guy working at the bike co-op made explicit what BCRider first stated: you've got to rub those down like crazy with the abrasive.

Speaking of which, I need to go re-patch the tube on my bike that's sitting. On the trainer. Its sort of an excuse not to ride the trainer.
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Old 01-15-10, 04:28 AM   #5
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The most common problem I have encountered is people not letting the glue dry all the way before applying the patch. The second one is not using enough glue to cover the patch. Third is debris left on the tube. And yes - scuff the surface up well! Yes - you can use an alcohol-wipe to clean the area - but make sure it's completely evaporated before proceeding. I wouldn't recommend using anything stronger. You run the risk of damaging the latex/rubber itself.

Good luck! You'll get it right.
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Old 01-15-10, 07:13 AM   #6
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Acetone will do it. The patch will weld on to the tube, never to come off again. I have to use acetone prior to patching Road Tubeless tires; it's the only good way to clean them for patching if one uses sealant inside.
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Old 01-15-10, 07:53 AM   #7
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I also have same problem after 30yrs of no trouble mine doesn't stick at all or sticks and then tire deflates a day later. I have tried all new glues different patches etc. I am leaving for a cross country trip Feb 1 and am worried about this. I can completely build a bike but not patch a tube. It is totally demoralizing.
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Old 01-15-10, 08:21 AM   #8
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As much as many people hate the things, I use Park GP2 self-adhesive patches and rarely have any problems. Only after 3 months did one of them develop a leak, because it was a patch placed over a seam on the tube. Aside from that one issue, they've done me well.
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Old 01-15-10, 08:30 AM   #9
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I've never had one come off, using only the normal stuff in a patch kit.

What they all said, and I "roll" the patch on with a round screwdriver head, or, even a round stone, pushing down very firmly. Same goes for patching tubeless tires.
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Old 01-15-10, 09:35 AM   #10
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Quote:
Originally Posted by markjenn View Post
Gentlemen, please explain what I'm doing wrong. I have been patching tubes for thirty years and am lucky to have maybe a 50% batting average with respect to a patched tube not slow leaking afterwards.

Checklist: I'm not stupid. I have a good patching kit (I typically use the Rema kit and patches.) I use fresh vulcanizing fluid. I follow directions, including roughing up the area, applying a thin layer of fluid, waiting five minutes, and then carefully pressing the patch down from the center out. But even when I do all these things, I often get slow leaks. And during the subsequent second attempt, I often note that the patch simply isn't sticking that well to the tube - it is pretty easy to pull it up from a corner. Shouldn't a properly-applied vulcanizing patch weld the patch to the rubber of the tube?

My theory is that there is often something on the tube which is preventing the fluid from working properly and from getting good adhesion. Would some alcohol wipes help? Would wiping down the tube with something a little more aggressive (e.g., lacquer thinner, MEK, acetone)?

I'm tired of messing with this to the point that I often just put in a new tube and throw the old away, even for the first puncture. But that seems like a waste.

- Mark
To me the difference was when somebody finally told me the reasons behind the patching procedures like eg. roughing the area up. Yes you are right in your theory about something on the tube that prevents the glue to work: It is mold release from the production that covers the tube, and the reason why you should apply eg. sandpaper before patching to remove this layer. I thought (like many others) that the reason to rough up the area was because this made the glue and patch bond better.

Engineer Jobst Brandt have written this excellent section of the RBT Usenet group FAQ. It is worth a careful reading:
http://draco.acs.uci.edu/rbfaq/FAQ/8b.1.html

The section "Leaky patches" may explain some of your problems; basically, don't patch and ride the tube the same day if it can be avoided. It is therefore common to just exchange the tube when on the road, and then patch the tubes in batches.
A day or two after I have patched such a batch, I fill them with air as a kind of quality control for bad patches or overlooked micro-holes. If the tubes still hold the air a couple of days later, I roll them up and place them in in zip lock bags to avoid abrasion failures when in my repair kit.

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Old 01-15-10, 10:03 AM   #11
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Do you put glue on the tire and patch? I rarely have a patch fail. Rough up the tube, put glue on the roughed up area, put glue on the patch, let both dry. When the patch touches the tube, they will stick, there is no moving it once they are together, so make sure you cover the hole.
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Old 01-15-10, 11:05 AM   #12
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Here is a really good thread on tube patching from awhile back. I learned a lot from it... including that the patches don't "weld" to the tube.

http://www.bikeforums.net/showthread...g-narrow-tubes

After which I upgraded my tires, and haven't had a flat since. Oh well.
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Old 01-15-10, 12:46 PM   #13
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Quote:
Originally Posted by leob1 View Post
Do you put glue on the tire and patch? I rarely have a patch fail. Rough up the tube, put glue on the roughed up area, put glue on the patch, let both dry. When the patch touches the tube, they will stick, there is no moving it once they are together, so make sure you cover the hole.
You may want to mention which brand of patch you're using. With the kits I get locally the patches are pre-glued and come stuck between a backing and a front film. The kit specifically says to glue the tube only.



More generally sticking the patch on too early is definetly not good. The glue not only has to LOOK dry but you should not be able to smell much, if any solvent. I find that this takes around 10 minutes or so. Maybe 15 in the winter when it's cold in the shop. But don't rush it. The glue is a contact type cement and will remain active for at least an hour.
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Old 01-15-10, 02:01 PM   #14
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Wow, I see that this is a thread that is both popular and comes up frequently. I'm surprised that something done by bicyclists this commonly is so sensitive to technique and prone to error. You would think there is a hell of an opportunity for someone to come up with a better system. Thanks for the comments.

- Mark
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Old 01-15-10, 04:03 PM   #15
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I replace the tube with a good tube on the road and take the old tube home. This gives me more time to analyze the cause of the flat.
After installing a patch I put a heavy flat weight on the patch to help squeeze out any air while the glue dries. Works every time.

Al
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Old 01-15-10, 04:29 PM   #16
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Quote:
Originally Posted by markjenn View Post
I have been patching tubes for thirty years and am lucky to have maybe a 50% batting average with respect to a patched tube not slow leaking afterwards.
Wiping with alcohol or lighter fluid is good. Otherwise, are you putting the right side of the patch towards the tube? The soft little-vulcanized rubber should be directed towards the tube. Are you spreading out the glue far enough away from the hole, significantly farther than the patch extends? Do you lose track of where the hole is after spreading the glue? You can mark the hole position with a cross whose arms extend beyond where the glue will be. If the patch has sharp vertices, you should round them with scissors. Are you unnecessarily trying to remove protective paper off the patch? It is better to leave it on the tube - it does not hurt and will eventually fall off. After patching, it is good to talc the glue area to prevent sticking to the tire.

Other than in difficult cases of vent area or making stupid mistakes along the lines above, I have no failures - rather I find it quite predictable. If you tend to end up with leaks, inflate the tube after patching, just moderately, and put it under water. You should be able to see small bubbles forming in the patch contact area, even if the leak is very slow. Normally, the patch should settle with the tube inflated inside the tire, but, in your case, it might be worth to shorten the turnaround.

Last edited by 2_i; 01-15-10 at 04:35 PM.
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Old 01-15-10, 04:34 PM   #17
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Quote:
Originally Posted by pmt View Post
Acetone will do it. The patch will weld on to the tube, never to come off again. I have to use acetone prior to patching Road Tubeless tires; it's the only good way to clean them for patching if one uses sealant inside.
+1
And ..With acetone(or lacquer thinner) you never need to sandpaper it...never had a failure..
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Old 01-15-10, 04:51 PM   #18
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I have found that a drywall sanding sponge enables me to get an evenly abraded tube very quickly. Years ago, an old timer told me to vigorously rub the back of the applied patch with a rounded tool, he used a pen-size device with a small roller on the end, until the cellophane comes off.
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Old 01-15-10, 05:21 PM   #19
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Some one else mentioned that they used the Park peel and press on patches, and had good luck. I have used that brand, and others, and have had no trouble at all. The plus's of the peel and stick is no glue no waiting, and the kit is just a small box. But with them too, be sure to buff the area really good.
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Old 01-15-10, 06:34 PM   #20
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Acetone doesn't come in handy little foil packs like alcohol does, thus you can't carry acetone in your seat bag unless you get a small bottle and take the chance of it leaking.

I too use Park Glueless patches and have doing so since they first came onto the market and NEVER had a failure and use them as permanent patches. I'll never go back to glue on patches again...not that their bad, in fact glue patches are quite good, but the ease of the glueless patch and never having to find a dry glue tube outweighs the old glue on patches.

You do need to buff the tube with a small piece of fine emery paper; but if you buff to hard or use too course of a emery or sand paper you can rub right through a tube especially a ultralight tube; thus buff lightly. Make sure you buff an area slightly larger then the patch will cover, then (if using glue) glue an area larger then the patch will cover, then press the patch hard on like others have said whether glue or glueless.

In the old days I too use a small tool with a small roller on it but I haven't used that in many years. You can do the same thing with your finger and thumb just roll the patch real hard with your finger on the bottom of the tube and your thumb on the patch and roll back and forth real hard and the cellophane backing will come off.

I always patch on the road mostly because I tour a lot and can't be carrying 4 dozen tubes with me so I can take home the leakers to fix when I get home!!! When I race I just replace the tube.
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Old 01-15-10, 06:44 PM   #21
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I haven't read any of the posts here except for BCRider's first one, and he has everything that I do except, if you're patching the tube at home, use a vice instead of your hands. Letting the glue get "milky" and then clamping the tube and patch at high pressure creates a chemical reaction that makes a really sturdy bond.
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Old 01-15-10, 06:59 PM   #22
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haven't had problems doing it with my hands
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Old 01-15-10, 07:07 PM   #23
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haven't had problems doing it with my hands
I'm not saying it's an issue, I'm saying that it creates a very strong bond that has never failed on my 1000mile-ridden patched road tube.
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Old 01-15-10, 08:13 PM   #24
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Acetone doesn't come in handy little foil packs like alcohol does, thus you can't carry acetone in your seat bag unless you get a small bottle and take the chance of it leaking
Yes, well, if you want to patch Road Tubeless on the road. you find a way. I use an emptied-out Visine eyedrops bottle. It's small and the tip makes it easy to apply the acetone precisely. No leaks at all.
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Old 01-15-10, 10:35 PM   #25
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here's how it has been successful for me.

scuff up the area and brush off any remnants with your fingers.
apply the glue in a thin, quarter-sized circle.
get antsy and put the patch on in 3-4 minutes.
push it on hard for a few seconds.
put the tube back in the tire, mount it on the rim, and pump it up.

maybe the pressure between the patch and tire helps create a strong bond, i dont know.
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