Wow, that's a strange one. Glad they are ok.

 

Metal grate bridges can freak out a rider if they are not used to them, just like riding on gravel.

 

This bridge is no exception in that feeling. I have ridden the Big Mac dozens of times and experienced the 'gravel ride' but this rider lost a wheel which caused the crash. I suspect this rider has also been on the bridge many times as he lives only about 2 hours away.

 

Yes now that I have had a chance to watch the video his rear wheel came of and his wife heard what sounded like loose change falling out of his pockets when it was the lug bolts coming out of the wheel. That can only happen if they were not properly torqued. I know of one other rider that lost a rear drive (not just the wheel) during a rear drive bearing failure and it separated from the bike.

 

That bridge is super scary for the first time. I went over it once and that outside lanes were close to park repair trucks so everyone had to do the steel grate. Don't look down as it is like 200 feet. Freaky. Whoever did the last wheel/tire change failed to torque the bolts. Could have cost lives. Motorcycle repair and maintenance is fraught with so much really dangerous actions. Makes me always worry about working on bikes. I make check lists, wake up at night wondering if I missed something. I have called folks to check something that I was worried about at 2AM. The wife wants me to stop working on other peoples bikes. I go slow, triple check things, stand back and walk around the bike checking each part I touched.

 

On the LT I use torque wrenches for everything. I actually enjoy using them. You just can't guess that it is tight enough. Also, you need to know that they are all equally as tight. The last time I had my tires change, I torqued them all myself once I got home.
Trust no one else.

 

I used to regularly ride across a steel grate bridge here in Georgia. It's been upgraded to a new concrete deck and is now much better. When riding over the grate, looking down is like looking through a giant cheese grater. With the gravel road feel, I was alwas extra focused when I rode that route. Glad the rider in the video was not seriously injured.

 

My take on this unfortunate event:
Primary cause was improperly torque wheel bolts.
I've crossed that bridge a few times, and it is a long, squirmy, ride.
Because of the depth of the "channels" in the bridge grate, the tires tend to jump from one channel to another, back and forth. That may have facilitated the predisposed loose wheel bolts to jiggle and "walk out" causing the failure to happen on the bridge.
Wikipedia: "Opened in 1957, the 26,372-foot-long (4.995 mi; 8.038 km) [1] bridge is the world's 29th-longest main span and is the longest suspension bridge between anchorages in the Western Hemisphere."