I'm trying to understand the basics of bike maintenance and I need some help, please. I have a Specialized Tricross Comp bike. I recently changed my rear wheel from the stock Roval wheel to the stronger and slightly wider Mavic A719 wheel. The A719 accommodates tires from 28c-37c. I use the Continental Grand Prix 4 Season 28c tire on my A719 wheel.
Here's the problem: my Continental 28c tire keeps deflating. Four tubes were flat before I realized that I needed to put rim tape. Then, I put rim tape or, rather, what I think is equivalent: I wrapped electrical tape around the rims twice and then I used the slightly thicker Babolat tape - it's a little tougher than duct tape and used to protect the head of tennis racquets - another two times. There is no problem with the spokes puncturing my tires anymore and there are no creases in the rim tape. My inner tubes are no longer going flat.
But then why doesn't the tire pressure hold? I fill it to 115 psi at night. In the morning, the pressure is around 60 psi. After 24 hours, the pressure is at 30 psi. But, here's the thing - no air is leaking. The tube seems to be fine.
Does anyone have any suggestions for what might be wrong?
Thank you so much for your help!