Originally Posted by
dddd
The most-common problem with patches that slowly fail is that the patch allows stretch, which thus also allows the glued part of the tube to also stretch into a state of tension as the inflated tube fills the tire.
With the tube itself stretched in tension, the patch remains pinned against the inside of the tire casing by air pressure, but the tube can pull away from the patch, starting at the puncture hole, since air can only get between the bonded layers at the hole.
Eventually, as it slowly peels away, the tube is pulled into a flat surface, like a drum head, until the "drum head" diameter reaches the edge of the patch, at which point the air rapidly escapes.
This may be true with patches that use 'rubber cement', i.e. the very cheapest generic patches. However, it's not true with cold vulcanized patches like the Rema. Cold vulcanizing goes beyond a simple adhesive bond and becomes part of the tube. The new bonds formed are almost indistinguishable from the original rubber. They won't peel away fromn the tube because they are
part of the tube.
Originally Posted by
dddd
BTW, today's inner tubes are highly variable in terms of their patch-ability, with some tubes having a slightly "gummy" surface rubber which is extremely slow to abrade away cleanly, and all types of patches (glued and glueless) are challenged by it's Teflon-like adhesive properties.
By contrast, tubes from back in the day would typically abrade cleanly, with no balled-up, sticky rubber having to be sloughed off continuously as it was being created by the sanding action.
I've not run across any tube that is unpatchable and I have tubes from many different sources. All tubes, even the old ones, have a mold release compound on the outside. The tube couldn't be removed from the forming mold without it.
The key to a successful patch is more involved with the quality of the patch...*COUGH* Rema...and allowing the glue to dry properly than with the tube itself.
A leak
through the tube sounds like the offending object hasn't been removed.