I had a tire blow on previous 5er. Was doing about 65 at the time. I actually heard a pop and happened to be looking in the mirror when it happened and I saw/heard the tire go. Never lost control and I got off the road quick enough that the aluminum wheel never got a nick in it. The fender well didn't fare so well and the 5er was in the shop for several weeks getting fixed.
I usually don't tow much faster than 65, if I do it is only for short periods like passing someone....