I've had a very good experience with biketiresdirect (as noted earlier, they sell more than just tires). I recently bought a new helmet for a price that was better than I saw elsewhere. A day or two after I received it I noticed, on their online site, the price was reduced another $18. I emailed their customer service asking if they had any kind of price guarantee since I just bought it and the price was reduced very soon after. They responded quickly and credited my credit card with that $18 savings. While I had purchased from them once or twice in the past, this definitely made me a fan.