Join Date: Apr 2007
Location: Lakewood, Washington
If the load rating is for the rails themselves, and not for the roof, I think you would increase the carrying capacity by adding rails. You are distributing the weight among 4 supports instead of two. If the situation were reversed and you were taking rails OUT I think everyone would agree that that WOULD decrease the load capacity, right?
However, if we're talking about the roof itself, adding rails won't change much. But, I know they hold over 150 lbs as is. I put a fully loaded topped on that weighed in excess of 250 lbs and moved from Augusta, GA to Missoula, MT without a problem.
I'm no physics major, so I can't say how MUCH additional bars would increase the capacity, but I think it would.
RIP - Silver '06 Limited; 5.7 Hemi; 2" TerraFlex Lift; 255/70R17 Bridgestone Dueler REVOS, Horizontal Inclinometer, Signal Frog Antenna Ball, Surco Safari 50"x50" Roof Rack, GetLost4x4 bumper, Bulldog 9k Winch, GetLost4x4 Rock Rails - (should have added a snorkel)