Originally Posted by FBinNY

One of the most important steps is to "stitch" the patch down. You can't do this with gentle finger pressure, you need intense local pressure to work the patch into the tube and make a proper bond. They make tire stitchers, which are basically wheels on a stick specifically for this job. You don't need to go out and buy one though. Anything that will let you massage the two together will work. I use the rounded end of a 6" adjustable wrench on a table top, using a rocking motion to do the job, you can improvise with anything, but take a minute and stitch the patch down, especially at the edges and you'll have better results.

BTW- if you use patches like Rema, you're also supposed to remove the cellophane on the outside after you've stitched the patch. The cellophane inhibits the curing process (according to Rema) and prevents good bonding.

BTW- there's also a bit of chemistry involved, and there are slightly different formulations of the butyl in tubes. IME- every once in a while you'll run into a mismatch that won't bond no matter how hard you try. In Germany, Rema offers patches of different material and glue for various types of tubes, but only one (the basic butyl) is sold here in the USA