OK...I was wrong. I knew there was a reason I went with four wheel instead of three. A friend had told me she had a problem with the three wheel and I thought it was tipping but now since I read the link below I remember what it was. I just did a web search and found that the three wheel ones are better for fast movements...they are more difficult to maneuver in slow speeds. Here is a link and a quote from that site:
<LI id=jsArticleStep1 sizset="114" sizcache="11" itxtvisited="1">Some strollers are specifically designed for faster activities, such as jogging, while others are definitely for more leisurely walks. Those that are meant for speed usually have three wheels instead of four for easier maneuvering.
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About Pet Strollers | eHow.com About Pet Strollers | eHow.com