What gauge tubing for floor frame

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Well-known member
Aug 2, 2015
Fort Worth
Was wondering what size and gauge tubing everyone is using for framing a new floor and trans tunnel? Want to cut out the old floor and build a new one. Also going to redo part of the firewall. Thanks and any help is really appreciated!
A properly formed sheet metal floor or tunnel doesn't require a tubing "frame". I see a lot of builds waste often-precious space with a bunch of intricate framework that is completely unnecessary.
I'm with BED
I don't use any frame work on my floors and firewalls. I use 16 ga. sheet metal on all the floors I do and weld it all together.
I bought a bead roller but haven’t taken it out of the box yet. Anyone have any pics or links to ones they have done without framework?
Not the best picture, but zero tubing in this Model A Roadster floor...


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I use 16ga hot rolled for the floor. It is softer, easier to work, and has a stronger weld than cold rolled. No structure underneath the floor, although it is bolted to frame cross bracing in a couple of places.

The floor cross pieces in the pic are primarily for seat mounting points, but also add considerable strength.

Welding in the trans tunnel today.


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I used 1/2" treated plywood for the whole floor in a '36 Ford truck. There is a light wall rectangular tube across, under the floor, between the frame rails, and about directly under the seat front, [near the top of the picture]. I've been driving this truck for a few years now and don't feel any problems coming on.


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Thanks for the pics. Some great work. Problem is I don’t have a large brake to brake the edges for back and sides like old floor has. I have a 30” brake for smaller stuff. So I’m not sure how to attach without an angle or tube frame around the rear of cab and sides.
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Dr. C, Thanks for questioning my hasty and generally unfounded and inaccurate statement. As you likely know better than I, the relative weld strength depends on many factors, including whether mill scale was removed on hot rolled, whether cold rolled case hardens at the edge of the weld, filler material, grade and quality of steel, MIG or TIG, skills of the welder, etc. From what I have read, the weld on cold rolled may be stronger in part because of more uniformity of the sheet and no mill scale. I simply prefer welding hot rolled and like its workability for floors ... and it is much cheaper than cold rolled.

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