I don't think you have been given the answer you a wondering, but I am just reading between the lines. I think we would all llike to just replace all 4 but you specifically asked if replacing only fronts would hurt anything, and no one has given you the answer. The answer is NO just replacing fronts will NOT hurt anything. It would obviously be better to replace all 4 if you can but we are not all made of money and you and your machine will be just fine if you only replace fronts. Been there and done that many times.