I'm trying to find some good info for this in the use of building chassis .

 

DOM is stronger, and more expensive. NHRA rules allow the use of a smaller wall thickness with DOM, so cages made with it can be lighter within the rules.

 

i'm not sure if the wall thickness can be thinner on dom than hrew(standard) tubing? I know thats the case with cromoly, but not sure about dom? not saying your wrong but I just never heard that, hopefully someone can chime in i'm curious to know.

standard tubing is hrew (hot rolled electrically welded) which has a seam if you look on the inside. dom (drawn over mandrel) is not welded so there is no seam that could fail. dom is slightly stronger but one of the great attributes of dom is the ability to tap it. you can tap the material for heim joints or what ever you need. you aren't supposed to tap hrew tubing. if it were me i'd build my chassis out of hrew(due to costs and it isn't dramatically weaker) and i'd build suspension componets out of dom. if weight is a concern then you could build the chassis out of cromoly then suspension componets out of mild steel dom tubing. it all depends on the intended application and how fat the wallet is!

 

SCCA, PCA, BMWCCA, , NASA, etc do not allow HREW. It is not as strong, and doesn't have a consistent wall thickness. It has been known to split in an accident. DOM is drawn over mandrel. That means after it is welded it will be forced over a sizing manual that equally sizes the tubing from the inside and also helps equalize the weld line.

Do not build a cage from HREW. It isn't worth your life. If you are too cheap to build it right don't.