Depending on the year of your car and the trunk lid, there are a few options. I've managed bikeshops for 15 years and have pretty much seen them all. The best seller we had was the Allen Rack. I think it was the 103A and sold for about $40. I don't know if they still make it, i haven't worked for a bike shop for about 5 years. Another option is a Rhode Gear Rack. they make different models to fit different cars and start around $50 -$60. The thing to keep in mind is to make sure your car is clean where the rack pads contact the car. Dirt can cause scratches from the vibration. Also, use padding or a foam block wherever the bike may touch the car or another bike. A good bikeshop should be able to help you with this and be able to show you how to mount the bike on the rack properly. I hope I was of some help, if anyone has any other questions on bicycles, I'll be glad to help.

Steve