Suspicious that you've got a leak in your tire but not sure. Try this simple tried-and-true tip from the pros. Blogger Pinny Cohen's mechanic taught him this painless method for quickly and easily detecting leaks, no special equipment required:
The last time I thought a tire had a hidden leak, he whipped out a spray bottle with a 20/80 mix of liquid soap and water. I was about to tell him "thanks, but I just got a car wash done the other week" when he started spraying the tire. In a small area by the rim, I noticed a neat effect. Bubbles started growing and bursting at a fast rate - a leak!
It's not a new idea, but it's one of those clever little tricks that's always good to know. Photo by modenadude.