I just bought my first bike in Jan. Since then I have rode just over 1000 miles. My tires look rought on the edges but not to bad. But, in the last few days I have notice a feeling in the rear that feels like a slight sway, kind of like low tire presure would feel. My tires have 38 lbs in them. I checked out the tire and there seems to be a flat spot in the middle, kind of giving the tire a squared off feel. Could this be what is causing it? is it time for a new tire? what is a good tire for street?