I recently took an old Brompton bicycle out of storage after several years. The tyres were deflated (unsurprisingly) so I pumped up the inner tube to check for punctures. I couldn't find any obvious punctures and the tubes did not deflate over the course of the next couple of days.
However when I put the tubes back onto the wheel they deflated within a few hours. Is this because the the inner tube has weakened over time and the pressure of the tyre is forcing the air out? Or is there another reason?
Many thanks in advance for any advice/help.