Tire size help needed

The actual size of the tire is what matters, not so much the rim size. For instance the stock 175/70 R13 tire is around 23 inches in diameter. To get the same diameter in a 14 inch tire you would need a 165/65 R14 would be real close. However a tire like a 185/70 14 would be much larger and wouldn't fit without hitting.
As long as the diameter is close and the tire clears it shouldn't cause many problems. I wouldn't try driving in snow or bad weather though as the tires likely won't have the same tread pattern, that can be much worse than being the wrong size.