All trunk racks will scratch your paint. There is no real way to avoid it...just minimize it. The rubber padding on the racks will shift when you tighten the straps...that will move any dirt that is on the paint. So I now try to clean off as best as I can the areas that come in contact with the pads. Then on the pads itself, I put a microfiber towel around the rubber. And of course when securing the bikes...make sure the handle bar is secured to the frame so the front wheels cant move and hit your bumper...and the back wheel should be kept from being able to spin because that will turn the crank and the pedals can scratch the paint. Then finally depending on the rack, secure the bottom half of the frame onto the trunk. Going about 40+, the bike looks like its hanging on for dear life

I have the Saris Bones 3 bike. Great sturdy rack...easy to fit onto car...easy to take on and off.