I recently purchased this rack for my old Univega. When I got it home though I tried installing it and noticed that my bike doesn't have any mounting holes near the seatpost. Is there any way I could install this rack on my bike or would I need to buy a different one that mounts to the brake?
P clamps are small vinyl covered metal loops that go around the stays and have holes in each end that line up when the P clamp is installed around the stay. You put small bolts/nuts through the holes and with the supports from the rack in place you tighten them up. That's what you need. The rack may have come with a bag of hardware that includes them, it's common to have to use them.