[JimD]

I don't have a hitch on my e88 yet but may do it. I currently tow with my Suzuki SUV. It has a class III hitch which has a 2 inch rectangular bar. It also has an eighth of inch or so clearance between the bar and the hitch. Depending on how the trailer is loaded it sometimes rattles. It only happens over bigger bumps unless the trailer is loaded improperly with too much weight in the back of the trailer.

With bikes on the back, I strongly suspect the rattling will be mostly the bikes and parts of the bike rack, not the bar fitup to the hitch. The weight of the bikes is going to take the slop out of the bar fitup and unless a bump causes enough acceleration up and down to overcome that weight, the bar won't move in the hitch. The way the bikes are held is unlikely to be as loaded (it could damage the bikes if it was) so I think that is where your rattling will come from. At highway speeds, I doubt you will hear a thing. Highways tend to be smoother than at least some secondary roads too. That may help.

I wouldn't worry about it. With a quality bike rack you should be fine.