I never had any luck the first couple of times I tried to patch a tube, so I gave up on it for years. When faced with a flat, I just put in a fresh tube but have still been saving the punctured ones. It's a quiet night so I decided to try patching again. I used one of those kits with the separate cement/vulcanizing fluid, not the quick stick-on patches.

One problem I had was that I didn't realize how big the patches were in relation to the width of the flattened tube, so there's a bit of the patch's edge that isn't bonded to the tube because I didn't spread the cement over a large enough area. Will this be a problem or cause of a leaky patch?

I've also read that a patched tube will sometimes appear to hold air when inflated freely outside a tire but then will actually leak when installed inside a tire. So should I take out the fresh tube and save it for emergency roadside flat replacement and install the patched tube to ride on? When I'm out riding, I don't want my spare tube to be a leaky one!

Get some REMA patches in the 16mm size.
You can lay the patch on the tube and trace around it with a pen to show the area that has to have glue applied.

In general, removing the "dead" (oxidized) rubber is the key.
REMA kits include a piece of sandpaper which works well.
The cheap kits with the little metal scraper are a PITA. They are akin to applying bricks vs REMA.

IF your hole is well centered on the patch, you should be OK, assuming an otherwise good patch job.

When I patch a tube, I let it sit for a day and then put it in a "shop" wheel, gas it up, and let it sit for a day or two to see if it holds air. Then, I'll install it and ride it. I never carry a patched tube that I haven't tested as a spare.

Ride the patched tube, & bring the 27 others that you saved up as well. One of them is bound to work.

A properly installed patch doesn't leak. If your edges aren't glued down, you haven't applied the patch properly. you may well be okay, depending on whether you got the patch centerd over the puncture, and the size of the puncture.

[QUOTE=Bill Kapaun;17665417]Get some REMA patches in the 16mm size.
You can lay the patch on the tube and trace around it with a pen to show the area that has to have glue applied.

In general, removing the "dead" (oxidized) rubber is the key.
REMA kits include a piece of sandpaper which works well.
The cheap kits with the little metal scraper are a PITA. They are akin to applying bricks vs REMA.
/QUOTE]

The purpose of sanding isn't just cleaning. It also greatly increases the surface area that's available to bond with the patch, which increases the bond strength. One of the tire repair training classes I went to had a demonstration about that. A section of automotive tire casing was preped for two patches. One was applied to a properly prepared area, done with a buffer. The other was applied to a bit where they used a razor to shave off the top layer of rubber, so it was clean and smooth. They got special patches with a stem that could be grabbed with a pair of pliers. The razor patch came off cleanly at the glue line. The properly done one the patch tore, leaving the layer in contact with the tire.

Also, sand and apply glue to an area somewhat larger than patch. That ensures that you get glue under the whole patch even if you don't put the patch on in exactly the right spot. The dried glue -- you do wait for the glue to dry before putting the patch on, right? -- is easy enough to rub off after you've applied the patch and stitched it down. (A tire lever or the edge of the patch kit box works well for that.)

I'm always surprised at the problems folks have with this but regardless of that I can say with some assurance that a patched tube is not particularly prone to any leakage. I have tubes that are in use for years with patches on them. Sometimes multiple patches. A good scuffing with the sand paper, a light application of the glue that is allowed to dry for 2 or 3 min (no more is needed) and then a firm application of the patch and you're done. I never carry a spare tube unless there is some big group or I'm doing a century. If you fail to get the edge glued you can lift it a bit, rub a bit of glue in there...try to give it a minute or so to dry out and press down on it. If the hole is already covered by the patch it won't make much difference. If you don't let the glue dry (it will not be entirely dry....but you can see the reflective shine become dull after a minute or so) the patch won't stick properly. A properly patched tire will not leak from the patch and the patch will last as long as the tube. Once a tube has three or four patches I'm apt to toss it for no particular reason but once you're comfortable patching a tube you'll have complete confidence in patches. One good reason to bring spare tubes is rain. If it's pouring out it can be a challenge to get the tube dry and properly patched. When mosquitos are bad here in Alaska I also may be more apt to bring a spare tube as I've patched tires while being eaten alive by mosquitos and that is no fun. Short of that....just patch and pedal.

Sanding also removes any mold release compound which can interfere with a good bond being achieved. The patch is not merely glued on, there is a chemical reaction between the vulcanizing fluid and the rubber of both the patch and tube, which when properly done makes them essentially a single piece of rubber. Regular rubber cement or contact cement does not cause this reaction, which is why they are unsuitable for this application.

Seems kinda funny that it's a lost art. Patching tubes was something all we kids learned to do and did as a matter of course back the '50s and '60s, usually taught to us by our fathers or friends.

Does anyone remember the old-fashioned hot vulcanizing kits? They had a clamp like this Vintage Tire Tube Patch Vulcanizing Repair Clamp | eBay
and the patches came attached to a tin container filled with some fibrous compound which you clamped to the tube and set afire to heat the patch and complete the process. Vintage J w Speaker Corp Match Patch Vulcanizing Unit Giant Oval GU 5 | eBay

Like the others, I use Rema patches and cold vulcanizing fluid exclusively. Let me add a couple of my tricks that have not been mentioned.

I use a plastic Rema patch kit box to hold the tube in place while patching. I've marked a center line on the box with a crayon. This allows me to center the puncture. It's easy to miss the hole after sanding. I'll clamp the tube in place with a clothespin to prevent the tube from moving, once the hole is centered. I'll then start sanding to clean the area around the puncture. The area sanded is always greater than the patch.

The cold vulcanizing fluid aka glue has to be dry before applying the patch. Thinner glue layers speed drying. I'll use only a small drop of the glue. I'll place that drop away from the puncture. I'll then spread the glue in a thin layer with my finger, covering an area that's larger than the patch. Any excess will be spread outside the patch area. I'll wait until the glue is completely dry. I won't blow on the glue to hasten drying.

Rema patches have a cellophane back that's scored in one direction. The scoring is designed to make it easy to remove the cellophane once the patch is applied. I'll start the cellophane splitting by folding the patch along the score mark. My reason is to make sure I orient the patch with the slit being crosswise with respect to the tube.

I center and apply the patch over the puncture holding it by the cellophane corner so as not to contaminate the underside. Once applied, I take a second Rema patch kit box and use it as a burnishing tool. I move the box's rounded corner from the center to the outside pressing down. The first Rema patch kit box serves as backing. The idea is to make sure all air between the patch and the tube is removed.

I usually don't have to wait too long after burnishing for the patch to cure. That's because I started with the glue already dry. It's time to remove the cellophane backing. The slit has been already opened a little. I'll grip the edges on both sides of the slit and stretch the tube. The slit will expand until the cellophane is in two pieces. The cellophane can then be removed from the center to the outside of the patch by folding the tube along the slit.

Finally, I've saved the talcum dispenser from an old Dunlop patch kit. I'll spray and spread some talc on top of the patch and excess glued area. This will neutralize it and prevent the patch from adhering to the tire.

I normally wouldn't swap a tube at home just to have the new one as the spare. Just put the patched tube back in the saddle bag, carry a patch kit and you're covered.

I can verify as an 80s kid, the idea of a "spare tube" was alien to me. We patched our tubes on the go.

Take one of your patched inner tubes with the exposed, unglued edges. Now take a pair of pliers and try to pull the patch off. My guess is the only way you'll get the patch off will involve tearing the tube apart. That's a long way of saying "I wouldn't worry about it."

I figure that if I already have the tire apart, there is no reason to not patch it, and put it back in! Save the new one for emergencies.

I use the handle of my flip tip screw driver as a burnishing tool.
Cheers,
David in Alaska

Find hole,scuff tube until it is dull everywhere the patch goes,apply glue AND LET DRY (it will become dull and dry to the touch) apply patch and press it down good...done.I leave the clear backing on,it ain't hurting anything.

If done correctly,you should not be able to remove the patch as soon as it goes on.

The biggest problem I see is people don't let the glue dry long enough.....It won't work well unless the glue is dry.Or they don't scuff it well enough,it won't stick well to an unscuffed tube.No shiny spots.

+1 its the surface Preparation of the Tube that makes the biggest difference.

Spread the glue widely over an area larger than the patch. LET THE GLUE DRY! It's better to wait too long than to wait too short. I once forgot to apply a patch 20 minutes after applying the glue. I put the patch on, and it held permanently.

Carry a spare tube. Take the bad one out, find the hole, sand well to remove mold release, put on glue. While waiting for it to dry, put the spare tube in the wheel and pump it up. Then put on the patch and pack that tube away as the new spare: Patching Tubes by Jobst Brandt

I'm a kid of the '80's as well...a kid from Brooklyn. We patched our tires on-the-go...but these days, I feel that maybe a spare tube might come in handy one time. Last time my wife's bike caught a flat, the tube opened up about a 1/2" gash. I tossed that tube.