Hey - I am having a weird problem with my bike that is making me crazy. It is riding like the rear tire is flat (or VERY low on air) but it is not. I notice it when I am seated on a mild incline and pushing hard. The bike seems to bounce/sway/vibrate. . .this is new and I haven't had the problem before. I just replaced the rear tire (it was worn) by moving the front tire to the rear and putting the new tire on the front. I then had a puncture flat a day or so later (small tack went thru the tire/tube). I have checked the wheel and it appears ok (spins even, etc.).

It is a road bike - Tarmac Pro with Mondo S-Works tires.

Thanks
Adam