Re: what roll cage tubing type
 

I built racecar chassis for several years & always used .120 DOM when I had a choice & never had a chassis fail certification. The DOM is much more consistent than the cheaper stuff. Actually the reason for using .134 is it is more inconsistent & is also much heavier. I would recommend talking with the NHRA Chassis inspector beforehand as there are variations from person to person in how they approach Certification.

There is undoubtedly a good reason for the disclaimer from S&W but unless something drastic has changed the DOM is better tubing. Your bender can also affect the thickness of the outside radius.

tubing
 

the issue is at bends the inner thickens and outer stretches hence reducing the wall thickness, get the SFI guide and build chassis to those specs, they are different to NHRA (thinner wall)

Yes, your posting is older, but we thought we would chime in just in case you haven't made your final decision.

This is ‘your’ life, so listen to those who know, and don't talk price, which is in this discussion, as that is not what this is all about.

We used DOM in this rollcage for our '99 Firebird, as it is recommended by most tech inspectors over Chrome Moly. Why? Most Chrome Moly cages will not pass an inspection without a pile of paperwork and certifications that most can't afford. Everyone here has heard of or seen cage failures because the welding process was Junk!

Our cage has 223' of DOM tubing. BUT, we went to the next safety item. Welding the main hoops to ¼” plates welded to the floor just doesn't cut it anymore, and you will see inspections that demand an Occupant Compartment Frame (OCF), which is what you see here.

For our design, we used a Nascar Spec. design, similar to our current Land Speed Race car.

Just our .02 cents, and hope this helps in your decisions.

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my opinion, dom is better more consistent.
get an SFI 25.x to match your needs.
nhra requirements are thicker than SFI. .134 wall is used because of stretch on bends.

I use .125 wall EW. never failed a 7.50 tag. can buy any steel supply

Following your mail. If you have to keep your weight down, before I built the cage, I would sonic test the tubing ahead of time...

the EWS is made from flat plate and electrically butt welded 1010 mat'l, the DOM is 1020 mat'l and cld draw over a mandrel and seemless, the carbon content is in the same range on both.