We purchased two sets of these and used them on the Yakima roof racks on our pop-up camper. Assembly took less than an hour and attaching the 4 bikes took only 30 mins. We had two bikes (one youth/one adult) that had thicker support bars, so we just took apart the crimp assembly, placed it around the supports and then ratcheted them down like they're supposed to. We traveled 600 miles at highway speeds and only had one tire wobble. Overall, we are very pleased with the cost and performance of these racks!
I purchased this top carrier to use on a 2008 Scion XD with no roof rack. It fit the car very well but the instructions to secure it to the car were very confusing. Extra straps were needed. It would secure as tight as I felt safe with, but did not move during the trip. It did flap a lot during the trip (straps? no skid pad?) and the noise sounded a lot like there was rain on the roof of the car. But it did it's job during a move, and for that I was grateful. I'd recommend it. Just give yourself plenty of time to figure out the straps if you don't have a roof rack.
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