I had two blowouts on downhill’s going about 40. Both times I happened to be going almost straight. I had no damage to the rim. After looking at the tires I found out why.
Both tires were 70x23 with Kevlar belts. When going straight the Kevlar belt flattened out and made the tire stick out past the rim on both sides evenly. On those tires you can feel the location of the Kevlar belt by hand. It saved my new Ksyriums both times.
The Kevlar belt has another hidden benefit, if you go straight enough it can protect your rims. cool.