I've had my stock rims and tires sitting in the garage for about 1.5 years. I know that after a certain amount of time dry rot sets in and the tires can be less than reliable. It's pretty dry here. Is there a way to check if they're safe?

 

Look @ the sidewalls carefully for any signs of cracking etc. You may even want to have the wheels and tires broken down and inspected from the inside......

 

If your garage is pretty well sheltered from the elements, then i dont see a big problem!