Wheel spacers,wheel adapters are 1 more part that can fail. And just because you buy the best ones doesn't mean they can't fail. They can work their way loose,have a manufacturing flaw,etc. They aren't legal in some states. The only problems I have personally seen is the studs that hold the adapter to the wheel, spinning in the adapter. I've hit a curb sliding sideways running adapters,bent the wheel,bent the control arm,wheel adapter appeared fine. Are they safe or did I get lucky,or a little if both IDK. I do know that in one of my GM training classes,one if the instructors basically told us anything not added is one less part that can fail. He also told us not to get a Cadillac with the first year option of anything. The Cadillac gets the cool toys first ,to keep the high end clientele happy. Cadillac owners will be pissed if their neighbors get electric ball scratchers in the Chevrolet before they were available in the Cadillac. But the first year is when they discover all the problems they hadn't thought of yet.