Does your Hardrock have 26" rims or is it a 29er? I have a Hardrock 29er and use 700x38 tires. I'm easily 4 to 5mph faster with the same effort on the street tires. It should have eyelets for a rack. They are on the seat stays about three inches down from the seat tube. If you have disc brakes you would need the rack designed for them.