It's true that you can have some crashes with the road with a big downpipe, attached is a picture of the shield I had welded onto my pipe (props to Kurt Ziem - my welder)

Please excuse the oil (cheap Mugen fake oil cap leaked)
You can see the scratches on the shield, but it's stainless, It will take years before it wears through. I only let it hit 2 times, I forgot to be extra careful on certain Michigan roads!!