After having a tyre blowout about a month ago I decided to buy 4 brand new ones. I opted for the Runway Enduro 616.
They put my normal 50psi .a week week later I checked them and all 4 were 1-2 psi down. I thought that they may have needed to settle in as they were new or something so I topped them up. This happened another 3 times over a period of about a month. I took them back today and when they tyre place checked them all 4 were reading 46psi. The garage checked 1 of them for leaks but couldn’t find any. In the end they said they would fill them with nitrogen as this would stop them leaking air. He told me to bring them back in a week’s time . i am not hopeful .any suggestions would be appreciated.
If you said you hadn't had them filled with nitrogen, I would have thought the air you've put in 'has cooled down'.
Similar to when you blow up an air bed... Read that somewhere you blow it up - leave it, then come back to 'top up'.
But as people have said, it could be a poor bead seal on the rim, maybe due to something as simple as rust. You may have to take the tyre off (again), clean the rim and refit. Cheaper than getting whole new rims.