Very Very sad deal. Seems rear wheel stud breakage happens more than it should. I know some Pro mods that tried titanium studs and broke some.
Perhaps studs should be larger dia, more of them, spread the wheel circle pattern wider.
I did hear mentioned that a retaining devise is being looked into.
I watched the finish last evening and they showed how far that wheel bounced. Lucky it did not hurt anyone else.
Wheels into the crowd have killed many people over the years in all types of motor sports. Usually fans.
I recall one wheel incident at the Indy 500 one year. It was when I was still working with the Indy crew for Bear Manufacturing back then.
That damn wheel bounced from the 4th. turn to the start of the straight away and went into the stands. If I recall the victim was from near here in Peoria.
I remeber one night at Princeton IL. 1/4 mile Dirt track. Street Stockers running 10 and 12 bolt GM rears with only C clip retainers pitched out two wheels with the axles still attached two times that night. Both times they damn near hit a group standing by the first turn opening to the pits. I guess in Princeton, IL. they never heard of Strange's axle retainer kit for C clip type axles.
The damn fools still stood by that opening!