I recently purchased a CCM Excelsior 700c Hybrid bike from Canadian Tire (off the shelf), and I've ridden it less than 10 times. Twice now the tires (one more so than the other, but still both) have gone from stiff to saggy in a span of 1-2 weeks. I'm no bike expert, but it seems to me that a new bike (even one off the display shelf) should not be doing this. Should i complain to C.T, take it to a shop, practice a new religion..?