Frame Material

I am going to be ordering some tubing to backhalf my truck. I was wondering what thickness you guy think is necessary, I was thinking some .188 wall 2x3??

yeah that would work. i build mine out of .083 2x3

for example the full frame drag cars use .083 to build their box frames also..
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it all depends on the vehicle. that might be ok for a regular cab s-10 but not a 4 door dullie. it might need a 2x6 1/4 wall. reguardless of the vehicle i would only use the 2x4 .25 material. i wouldnt care if it was a little bit of overkill. if that wont fit run the 2x3. and esp if your going to drag a lot. all of those sparks are the bottom part of your frame and the last thing you want it your truck falling apart and hurting someone cause you didnt engineer the frame correctly. do it right the first time. good luck with the project bro