Now it’s flat, now it’s not. Ideas?
Details: Rode home from yesterday’s ride fine, rear tire properly inflated (by my low standards anyway. Grin.). This am: completely flat. Because of noise, rather than change the tube, I pumped up the tire with my shop pump and rode to a trailhead. ten minutes later, it’s at half inflation (20 psi rather than 40). I ran my trail, returning to a completely flat tire (as expected). Pumped it up. Trying to get the Zefel pump off was hard and the valve stem plug looked odd, like it had partly come out. Two hours later, it’s still holding air just fine. Scratching my head.