I recently bought a huffy cranbrook that came with these good looking fenders. These fenders were probably the cheapest metal at the bottom of the bin and I'll tell you why. I hand bent these to adjust them for fitment of some different wheels. They will also rattle at any speed because of all the wobble in them. Let's get into the real subject here why I will never have fenders on my bike again.
It all started out with a nice cruise. No problems on the bike at all in the past week. It was a simple cruise until I heard a terrible rattle. Sure enough I looked back and the fender had snapped at the frame mount beneath the seat. This is how the bike looked with fenders before anything had happened.
Fenders added a nice touch and shielded me from any water or dirt that might flick up onto my back. They had held up for the past week and what would make them break if they lasted a week? This little rattle wasn't any immediate danger to me in anyway. Then bang it happened. The wheel locked up and I stopped very suddenly. Luckily for me, I was going around 10mph slowing down to a stop sign a block from home. I wasn't injured and the bike wasn't crashed, but if I was going for a top speed run I would have been taking an express ride to the hospital.
Anyways, what the point I am trying to get across is that fenders can and will mess you up if they get enough vibration. A 30mph crash on a bicycle will cause some serious damage and I wouldn't like seeing anybody on this forum in that situation. So be very cautious on the items you add to your bike. Both fenders have been completely removed from my bike now. One not by choice.