Bicycle Mechanics - Theory of puncture repair

The main steps of patching a tube are:
1) Sandpaper around the hole
2) Apply glue around the hole
3) Wait
4) Apply the patch

Which of these is the most important? Which is most likely to cause a bad patch?

I ask because I'm having a low success rate with patches and wondering what to improve. Is it important to sand the seam all the way down? Is there a technique to squeezing the patch on so it holds? Etc!

Steve

What to improve:
Carry a spare tube!

Exactly. I have lots of spare tubes, all with holes in them. I want to repair them to take with me.

The "sanding" is really just roughing-up the surface so the glue sticks better. You want the surface to be clean before applying the glue. Letting the glue dry before applying the patch is important.

What sort of failures are you having? The patch not sticking? Have you checked the inside of the tire to make sure no sharp object is stuck in there?

Make sure you apply the glue to the tube and not to the patch otherwise it won't stick, and also make sure the area of the glue on the tube is greater than the size of the patch. It doesn't matter if you have glue outside the edges, it dries quickly and can be rubbed off. Blow on the glue before applying the patch, it looks like it turns to ice but it sticks better. I would put something to press down on the new patch before pumping up the tyre.

Just to add: after sticking the patch down, don't neglect to remove the backing if it has one. The patch needs to stretch with the tube when it's inflated, and the backing won't stretch. It'll pull up the edges of the patch. As stated, make sure that the glued area is larger all round than the patch, and that the latter is centred accurately over the puncture (which can be marked with a thin coloured crayon if it's very small. Dust over the whole repair with French chalk or talc to stop that excess adhesive sticking to the cover. Do not inflate the tyre until it's mounted inside the cover. As someone rightly suggested, this whole meshugas can be avoided on the road by carrying a spare tube, then you can do the repair at your leisure in ideal conditions.

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I always carry a spare too.

When I get a flat, I still do the roadside repair, but I put in my spare tube and put the repaired tube back in my bag. That gives the glue some time to "cure" . . and It'll be ready to use later if I need it. . . you never know. Weather or not the glue benefits from this curing or not . . .I don't know . . .but I don't have problems from repaired tubes either. :thumb:

The "sanding" is really just roughing-up the surface so the glue sticks better. You want the surface to be clean before applying the glue. Letting the glue dry before applying the patch is important.

What sort of failures are you having? The patch not sticking? Have you checked the inside of the tire to make sure no sharp object is stuck in there?

I use this rather than an abrasive. The "sandpaper" and/or "cheesegrater" will score the rubber, sometimes deeply. Not good.

As far as "roughing" the surface, what is necessary is the removal of the mold-release compound used in the tube's manufacture. Leveling any seam is good too. Expose pristine rubber and the properly-tackt glue and patch can be used immediatly, and will not fail.

That's where the blade (especially a straight-razor blade as it is very flexy) is good. A little spit, judicious scraping, some rubbing alcohol = good rubber ripe for the patch.

I patch until I can't--which has not yet happened--or terminal tube failure (usually age induced). One time, at speed, I picked-up a cotter pin. Eight holes before I could stop. It is still in the rotation. The tire's threads, however, did eventually fail from this.

I'll shill Slime's Classic Patch Kit. It's a good value. Seal the glue well, though; otherwise it will dry-up on you, most surely.

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I always carry a spare too.

When I get a flat, I still do the roadside repair, but I put in my spare tube and put the repaired tube back in my bag. That gives the glue some time to "cure" . . and It'll be ready to use later if I need it. . . you never know. Weather or not the glue benefits from this curing or not . . .I don't know . . .but I don't have problems from repaired tubes either. :thumb:


+1.

Unless I'm inbound a couple of mile from base, then I'll wait until I'm dry and do the repair.

The important steps are sufficient glue to completely cover the patch and a bit beyond and waiting for the glue to dry.

On the road I carry the Park GP-2 self-adhesive patches.
They are simpler and quicker to use, and I haven't had any failures.
(I do carry a spare tube just in case of major damage.)

Once I get home, I swap out the tube with a previously patched (or new) tube.
The self-adhesive patch is removed and a permanent patch is installed.
The patched tube hangs on the wall until it is needed.

When patching at home, I use a shop clamp to squeeze that puppy on there good.

It can be quite convenient to just fix the tube without taking the wheel off, esp the back wheel where it can be a bit fiddly and messy if you don't have gloves.

1) Sandpaper around the hole . Yep. Make sure all of the smooth rubber is roughed up. You don't want deep gouges but you do want no sheen at all on the rubber. Then you want to make sure all the rubber dust is off the area.

2) Apply glue around the hole . I usually use the end of the glue tube to mush the glue around before it dries, to make sure any rubber dust is in the glue rather than on the surface.

3) Wait Important. Make sure the glue is completely dry, but don't touch it. The glue surface will be slightly shiny when ready; you'll learn to recognize this.

4) Apply the patch. When you remove the backing from the patch, make sure you don't touch the exposed surface. Stick the patch over the puncture, and then use the end of your plastic tire lever to go back and forth over the patch. If the patch lifts off then one of the earlier steps has been compromised. It should stick down well.

5. Use a good patch kit. There are differences. I use the Rema Tip-Top and have no problems, but there are other kits. The better kits have individual patches with foil on one side and plastic film on the other.

1) Sandpaper around the hole . Yep. Make sure all of the smooth rubber is roughed up. You don't want deep gouges but you do want no sheen at all on the rubber. Then you want to make sure all the rubber dust is off the area.

2) Apply glue around the hole . I usually use the end of the glue tube to mush the glue around before it dries, to make sure any rubber dust is in the glue rather than on the surface.

3) Wait Important. Make sure the glue is completely dry, but don't touch it. The glue surface will be slightly shiny when ready; you'll learn to recognize this.

4) Apply the patch. When you remove the backing from the patch, make sure you don't touch the exposed surface. Stick the patch over the puncture, and then use the end of your plastic tire lever to go back and forth over the patch. If the patch lifts off then one of the earlier steps has been compromised. It should stick down well.

5. Use a good patch kit. There are differences. I use the Rema Tip-Top and have no problems, but there are other kits. The better kits have individual patches with foil on one side and plastic film on the other.

If you are obsessive, clean with alcohol before #2.

http://www.made-in-china.com/image/2f0j00mMLQuOFaJfztM/Alcohol-Pad.jpg

I have never had a patch fail, but I have never tried the glueless type. After I apply the patch to the tube, I put it down on a hard surface and rub the back of it with my tire lever. It allows all the air bubbles to come out and makes sure you have good patch to tube contact.

I have finally become a successful patcher. Most important change for me was the "wait" part. Now I time myself and wait ~10 minutes after putting glue on before sticking the patch on the tube..

Also, now I inflate the tube slightly and try to make it close to its inflated size before applying the patch.

Then I install the patched tube and pump up right away.

What patch kit are you using? How old is it?

I didn't have luck with patching until I picked up a proper patch kit @ the LBS. One of the touring ones with the correct vulcanizing fluid. The key after that was making SURE I waited the instructed amount of time before removing the plastic cover. Making sure you put a wider spot of glue than you need is important also.

In response to a few comments:
- Yes, I carry spare tubes and repair them at home.
- I tried the Slime glueless patch kit. Of the 6 patches in the kit, 4 failed immediately. One failed a bit later. The last one looks like it's about to fail. With each one I inflated the tube a bit so the patch wouldn't have to stretch too much, but when I deflated it, the patches seemed to shrivel up and lose contact.
- "What patch kit are you using? How old is it?" - one brand is "thumbs up" (made in Taiwan) - a pretty basic one from LBS, has patches with foil/plastic. Not old.
- "What sort of failures are you having? The patch not sticking?" - generally it's a corner or two not quite sticking.


Just to add: after sticking the patch down, don't neglect to remove the backing if it has one. The patch needs to stretch with the tube when it's inflated, and the backing won't stretch. It'll pull up the edges of the patch.

That's interesting. I often find it hard to remove the backing because it ends up glued to the tube. And if I try and peel it, sometimes it peels the patch off too.

After doing a few more, I think what I'm mostly doing wrong is not making the glued area big enough. It seems to me if you even have one corner that isn't well glued, the whole thing can peel off. I'll also try waiting longer.

The one big thing that has helped save my sanity is testing the tubes before using them. After patching, I inflate them to, then leave them overnight. If they're still inflated in the morning, I'll trust them.

The main steps of patching a tube are:
1) Sandpaper around the hole
2) Apply glue around the hole
3) Wait
4) Apply the patch

Which of these is the most important? Which is most likely to cause a bad patch?

I ask because I'm having a low success rate with patches and wondering what to improve. Is it important to sand the seam all the way down? Is there a technique to squeezing the patch on so it holds? Etc!

Steve

3) Wait

Don't rush the time for the solvent in the glue to evaporate. "Wait" means more then 30 seconds. 2 minutes is good, 10 minutes is better, overnight is a little long but it does work;)

Carrying a spare tube is better and then fix the hole at home. But if you have to fix on the road, relax and wait awhile.

The relatively new Park Tool GP-2 glueless patch-kits streamline the process. There is no glue to wait for to dry. Clean. Sand. Peel. Press. Go. The whole kit is about the size of your thumbnail.

I often find it hard to remove the backing because it ends up glued to the tube. And if I try and peel it, sometimes it peels the patch off too

The last patches I used here were called Cure-C-Cure. They had a foil covering on one side, which you removed before sticking them down. Then you were confronted with a paper backing, which had a slit down the middle, so you could remove each half from the centre outwards. This took care of any tendency to pull at the edge of the patch. These patches were also chamfered so they blended into the surface of the tube. By contrast, the old Dunlop patches we used in the sixties were the same thickness all over, so they lifted at the edges much more easily.

Make sure you apply the glue to the tube and not to the patch otherwise it won't stick, and also make sure the area of the glue on the tube is greater than the size of the patch.

for my problems with bad patches it was this and the proper wait time.

Maybe you're not waiting long enough or adding too much glue, which would increase the time you need to wait. I have left the glue to dry all day in the sun then overnight before joining patch to tube, and it worked like a charm. Not that you have to wait so long (I forgot I left a patch job unfinished), but too long is definitely better than too short. Leave your home patch repairs to dry overnight before putting the patch on and see how well they stick.

there is also mold release on the tubes. It is a substance which keeps the tube from sticking to the mold when it is manufactured. There is also sometimes cornstarch. Clean those off very well, even if you have to rub the tube against some concrete. I feel that is better than the metal scrapers they give you if you wipe off the grit.

I use the plainest patch kits you can buy in the hardware section of the grocery store. They work great.

For patching holes at home, as opposed to on the road, try this;

1) Briskly rub the tube, around the hole, with Brake Klean or other solvent. What you are trying to do is remove the gloss, or sheen from the rubber

2) Apply a THIN, even coat of glue, on an area that is larger than the patch you are going to use.

3) WAIT until the glue is completely dry. Apply the patch, and use a wallpaper seam roller to roll and apply pressure to the patch. I do this with the tube on the flat area of my bench vise. Use some muscle here. Wait a few minutes, and peel off the clear film on the patch. You're good to go. bk

I disagree with the posters who think it's necessary to go nuts on the pressure. Press the patch on good and tight with your thumb and it will be fine. Provided the glue is completely dry. (not that pressure will redress a lack of dryness.)

For sure on the dry time. I'm always impatient. I also trim the precut square patches to round or oval to eliminate sharp corners that peel up. I usually roll the patch with a deep socket to firmly attach it.

So, does anyone use glueless patches as their permanent puncture repair method? I've tried the Slime ones and some others that look like this (http://www.campmor.com/wcsstore/Campmor/static/images/bicycling/54019.jpg). Neither looks as convincing as a well done glued patch. I can see the benefit as a quick repair job on the road, but not really for a permanent fix.

Getting back into bicycling a few years ago, I tried one of the cheap dept. store glueless patch kits (expecting permanent repair) and had a lot of failures (usually within a day or two). I am sticking with the around $2 patch kit with the tube of glue.

When I was a kid I'd use the pre-cut (about a sqare-inch in size) patches, but now I usually cut them into smaller semi-rounded (aprox. square-centimeter) patches. I do keep bigger patches on hand "just in case". The patch size probably has little to do with the repair success rate, but it just seems a waste to use such a big patch, especially relative to a skinny 700 x 25 tube.

I lightly use the metal "scrapper" (that comes with the kit) to ready the surface area. I don't do anything special when patching over a seam. I read somewhere to put a THIN layer of glue on both the tube "patch area" and the patch itself (repair side, of course), so this is what I've been doing. I wait for the initially-clear glue to "gloss over" and get a white-ish look to it (I might blow air on it to hasten this). The "gloss-over" of the glue usually just takes a minute or two. Then I just press the patch down on the tube with my thumb (with the tube laying against a hard flat surface, or just laying against my forefinger). If I see the edges of the patch not making good contact (often this will happen with just one small edge-section of the patch) I will take a toothpick and work some "new/fresh" glue into the "un-stuck" area, blow/wait on it as before and press again. Once I have a "visually-acceptable" patch everything is good-to-go (once I was patching in 90+ degrees and it took me three attempts with three new patches to fix the flat, that was before I carried an extra tube and fixed my flats at home).

From reading all the comments I would say one big similarity for success is letting the glue "cure" properly before attaching the patch to the tube. I don't think it can be stess enough to take your time and "take-notes" mentally when you succeed/fail. Ask yourself what you did right/wrong and apply that knowledge on your next attempt.

One definition of "A really long time" is sitting alongside the road, in the rain, waiting for the damn glue to cure so you can place the patch. I had a simultaneous front/back flat riding home from work (in the rain) last week and only had one tube with me. Had to patch the other one roadside. It seemed like FOREVER. :)

For patching holes at home, as opposed to on the road, try this;

1) Briskly rub the tube, around the hole, with Brake Klean or other solvent. What you are trying to do is remove the gloss, or sheen from the rubber

2) Apply a THIN, even coat of glue, on an area that is larger than the patch you are going to use.

3) WAIT until the glue is completely dry. Apply the patch, and use a wallpaper seam roller to roll and apply pressure to the patch. I do this with the tube on the flat area of my bench vise. Use some muscle here. Wait a few minutes, and peel off the clear film on the patch. You're good to go. bk

+1,,, I use acetone or lacquer thinner

Bud

This seems like such a mysterious and complicated process that I can't imagine how I've gotten by with just casually patching tubes and tires for the last 60 years, for myself and commercially! Perhaps the patch kits should come with instructions?

This seems like such a mysterious and complicated process that I can't imagine how I've gotten by with just casually patching tubes and tires for the last 60 years, for myself and commercially! Perhaps the patch kits should come with instructions?

One could be a snob and say "it's more of an art than a science"...I think different people read instructions and have different "interpretations"...some here have really emphasized putting a lot of pressure on the patch after applying it to the tube. Some say "wait a good while" for the glue to "dry" before applying the patch (I always feared the glue would become completely dry and useless, so I usually only wait a few minutes for a glossy-white-ish look to the glue and then apply).

Apparently there is a lot of room to put one's own personal "twist" to tube repair while still, as a group, we are mostly having success (even if one individual leaves out someone elses "must-do" move). I don't have bike-savvy friends to show me proper mechanical proceedures (although there may be a video of tube-repair on youtube), but if you can watch someone (who's done dozens of good tube repairs) while they're doing a tube repair then that would go a long way in helping a newbie "get it".

A side note, I just remembered this, when I was a kid (30 years ago) one of my friend's father actually lit the glue (while it was on the tube) on fire for a second or two, blew out the fire, and then applied the patch. I don't know what kind of glue and patches he was using, but thinking back it sort of blows my mind. I have never ever considered that technique...but I do wonder if it has any merit.

So, does anyone use glueless patches as their permanent puncture repair method? I've tried the Slime ones and some others that look like this (http://www.campmor.com/wcsstore/Campmor/static/images/bicycling/54019.jpg). Neither looks as convincing as a well done glued patch. I can see the benefit as a quick repair job on the road, but not really for a permanent fix.

I use the Park Tool GP-2. They work just fine. As strong as the rest of the tube.

That's interesting. I often find it hard to remove the backing because it ends up glued to the tube. And if I try and peel it, sometimes it peels the patch off too.


Yeah, I just leave the back on to avoid pulling an edge up. No problems.
I ride 700 x 23 tires and find that many patches are too big so I trim them to fit the tube better. But I do all of my patching at home. I also place a heavy weight on the patch while it dries.

A side note, I just remembered this, when I was a kid (30 years ago) one of my friend's father actually lit the glue (while it was on the tube) on fire for a second or two, blew out the fire, and then applied the patch. I don't know what kind of glue and patches he was using, but thinking back it sort of blows my mind. I have never ever considered that technique...but I do wonder if it has any merit.

They don't call it vulcanizing for nothing;) I think the application of heat was pretty standard until someone came out with a 'cold vulcanizing' compound.

>I also place a heavy weight on the patch while it dries.

Yeah, I've been using a bookcase :) But at the advice of another poster in this thread, I'm trying without. Did two last night and they still look good. I am finding that I'm getting much better at telling visually when a patch is going to last forever...

I'll have to try cutting down the size of patches - mine are really too big for 23mm tubes. There are a couple of huge (5cm) ones that I'm tempted to cheekily use to patch an exploded tube (the whole is millimetres shorter than the patch). But maybe I'll cut them down into smaller patches instead...

I'm finding something zen-like in the whole process, like whittling wood or something. I always had this huge fear of patching because I had such a low success rate, and it was so disheartening to patch then have the patch fail ten minutes down the road.

I worked out that I have something like 16 tubes, 6 of which are on bikes, and lots of other lying around with holes in them. Somehow with only two different bikes I have four different kinds: 700c 32mm, 700c 23mm, 26" 40mm presta and 26" 40mm schrader (useless).

Maybe when I master tube repair I'll move onto something really difficult like replacing spokes :p

Steve

The punctures that I've fixed have been the size of a pin-prick (or, in the case of snake-bite punctures, two pin-pricks) so relatively tiny (somewhat-rounded centimeter square-ish) patches worked fine (I think I have, in the case of a snake-biter used a still-small but more rectangular patch that covered both holes at once.

It would be a greater challenge to fix a larger "gash" in a tube, but I suppose one could give it a try if the patch used will cover the whole "wound" (I would want the patch to cover the hole and then spread out a least another centimeter over the "solid" tube surface surrounding the hole...if that makes sense).

I have a lot of tubes lying around of various sizes and conditions. When I got back into bicycling a few years ago I went in several different directions with different bikes and abandoned projects. I tend to hang on to things too long and tell myself that they might be useful someday...I guess there are worse habits/flaws one could have.

They don't call it vulcanizing for nothing;) I think the application of heat was pretty standard until someone came out with a 'cold vulcanizing' compound.

There used to be "Hot Vulcanizing" patch kits that included a clamping piece, patches and little tin containers of a chemical that burned to heat things up IIRC. The clamp squeezed the tube, patch and heat source together and then the heat source was lit to vulcanize the patch to the tube. I so not remember for sure if any form of vulcanizing cement was used too but do not believe so.