Originally Posted by
jdfnnl
having been a longtime believer in patches as a way of salvaging tubes and saving them from being trash, lately I have been noticing they just don't hold up sustaining normal road tire pressures (100+ psi). Patches really shine whenon a ride to remedy a flat if one is without a replacement tube, but otherwise it seems I have lost faith in the humble patch. This after recently confirming a front wheel repeatedly deflate from around 110 to remain around 40-50 and I suppose this was the last straw. I do a fairly thorough job of applying the patch, starting with a vigorous sanding out of all the ridges, before an even spread of cement that dries until tacky and then bam with the patch. Do any road riders avoid patched tubes like mushy wheels, or do some have better trust in their constancy and would say my method must be flawed somehow or that I am surely using old vulcanizing fluid.
There are several problems that I observe with people patching tubes at my local co-op...even from the volunteers who should know better. First, start with a
proper patch kit. Most people use the cheapest patch kit they can buy and then are disappointed with the results. Cheap patch kits use rubber cement to make the patch. It works but not as well as it should. Rema patch kits don't use "rubber cement". They use a 2 part system that includes an accelerator chemical in the vulcanizing fluid...
not rubber cement...and a second chemical in the patch that forms new rubber bonds. Done properly, the patch becomes part of the rubber over time and makes a much stronger bond.
Second, let the glue
dry. Not until it is "tacky" or no longer tacky. You can't let it dry enough. Or, more specifically, letting it sit for longer won't hurt anything and will actually help. I've forgotten a patch job in the garage for weeks and the patch stuck to the vulcanizing fluid perfectly fine. If, however, there is still any solvent under the vulcanizing fluid, the patch won't stick and the chemical reaction won't proceed on Rema patches.
Third, resist the urge to "check your work" by refilling the tube and dipping it in water. The Rema patches make a very fast bond. The chemical reaction starts almost immediately. Even the rubber cement based patch kits bond quickly but they don't initiate any chemical reactions. However, when you blow up the tire to "check" the patch, you are stretching the tube away from the patch and lifting the patch off the tube. The patch can start to leak because you've pulled the patch away from the hole.
The best thing to do is to put the tube back in the tire and inflate it...after checking for what made the puncture in the tire in the first place. The pressure will evenly press on the patch and let it, if you are using Rema patches, cure properly. Even if you just fold up the tube and let it sit in a seatbag, the patch will have time to cure and make a better bond.
Finally, the vulcanizing fluid doesn't age appreciably. As long as it has solvent in it, it will still work, no matter how old it is. Same with patches.