My experience was with the bigger ones falling of the trailers. Last month I ran over a big stone in rayyan, which fell off from a trailer. I didn't see it while it fell because there was a car in front of mine, and this guy somehow managed to avoid the stone and I saw it too late to avoid completely. My rear wheel ran over it and was broken and the tyre bursted, I had switched to 17" rims with low profile tyres from 15" stock wheels last year. Fortunately I had my stock wheels with me, never sold them, so saved further loss. still had to buy 4 new 15" tyres :-(