I've got a lumber rack on my truck (3500 drw) and I'm wondering how much weight I can load on it. The bed rails are going to fail long before the rack does, so the question is how much weight can the bed rails handle?

I've got a few hundred feet of steel tubing in 20 foot sticks i need to move, and I need to decide if the rack can handle it (within a couple of trips at least) or if I need to rent a trailer.

 

If it were me I would rent a trailer. I am not sure of the weight capacity but I do know that the metal in trucks now a days is nothing like trucks built back as late as the 70's. Case in point are camper achor tie downs that are being built these days because of the lack of solid metal truck beds. My friends Toy Tacoma bed slit apart from his lumber rack, granted it was a foreign vehicle, non the less these older Toys had better metal in them too back in the day.

 

If you have a manufactured rack, check the load capacity of the rack. Manufacturers never exceed the limits of the truck. My Thule Pro rack has a load capacity of 750lbs. If you or someone else made the rack, I would stick with that 750lb capacity. 750-1000lbs seems to be the norm for max load.