Coleman ABS roof rack

[fatmax007]

Hi all, I've read so many posts on the subject I'm sick of it but I have the sag in my '99' niagara and a few good cracks in the front of the top. From what I gather, a roof rack can fix the sag problem and the sides from bowing out but where is the presure coming from to bring on the cracking? I would think that the stress is due from the sagging ? Anyway, turns out I am a metal fabricator and aluminum is my favorite so I'm going to build a truss design rack I saw on some pics out of some 1x1alum tubing and see how it go's. I know it'll work since I'm going to clad the sides with some 10gauge aluminum sheets. My one question is this: if I get the roof back to its original shape will the stress cracking stop ? Thanks for your time,