they only rust because there's no sealent between the flares and body. In going to put a heavy bead of clear silicon to seal out moisture getting trapped under the flares and such. As well as cover that area that the flares cover with por15 or truck bed liner inside and out. They'll never rust again. Lol.

 

Chassis saver paint works incredibly well too. I used it on the underside of my mower deck, and that stuff is TOUGH. I couldn't even sandblast it off again....... (cleaning up mistakes, needed a grinder.) Its also cheaper than POR 15.... though still, not inexpensive by any stretch of the imagination.

 

While that might be part of it I believe that a significant portion of it comes from the backside when the fenders are insufficiently flushed out during a wash. Years of rust belt salt and sand get packed up in there and start the process. I think it doesn't help that flares on the outside keep the surface from being cleaned or waxed either.

Again I'm happy for you if that's what you want but they're not my thing. If I replace the bed / fenders on my Dakota I will probably look for stuff from the south and either remove the flares or find a bed that never had them.

Steve