On Friday, December 6, 2019 at 5:06:07 PM UTC-8, Dirk_PW wrote:
I like the cheap plastic fenders because they act as a weak link when something hits them. They shatter instead of transferring the impact loads to the side of the trailer. If something hits a metal fender, don't be surprised if it bends or wrinkles the side wall of the trailer where it is mounted. Other road debris can slam into the fenders that can do more damage than lost tread.

I've had both, and, no, I haven't seen any damage transferred to the trailer body (fortunately!). The damaged metal fender had to be replaced. Replace your tires at reasonable intervals; when they blow you will have to replace them anyhow, along with the fender.

Tom