I installed luggage racks on my '99 Jeep Grand Cherokee almost a year ago. They have worked fine for 11 months, installed to hold the tailgate. I happened to go skiing and it was very cold at night. The temperature was below zero and I was at 9500 feet. I opened the back door, one of the pillars started hissing and slamming, and the back door started falling. I think the problem came from a combination of very cold air and altitude. I contacted the company and they replaced the shelves free of charge. I installed it in about five minutes and my tailgate was back to normal. In about three weeks I will be skiing again. If I don't come back and post again, everything is fine.