Chassis Material

[rouse]

Just my "2 cents" then I'll shut up, ERW, DOM, are fabrication process, and have nothing to do with the alloy of the tubing.

When buying, and/or selecting tubing, you select the material by  ASTM # , and then decide the fabrication technique Ie, seamless, ERW, DOM, and the finish condition such as Hot Rolled, Heat Treat, as Rolled, or Normalized.

So; ASTM#*****+ Fabrication technique+ finish condition, and your ready to place your order.

Rouse

[Stainless1]

The nice thing about LSR is it is grass roots racing.  If you are a decent weldor, then you can build the cage that protects your life.  Most of us are  more comfortable welding mild steel than CM.  I finally built a CM axle, but not without talking to the pros about what I should do to normalize.  Fortunately the guy that builds the axles for Speedway lives in Wichita 
So weld what you are comfortable with, meet or exceed the size requirements in the rule book.  Don't worry about the weight.  A light car is not necessary, a car that can withstand a lot of punishment is.

Remember who is driving 

[kiwi belly tank]

I think the welding thing is probably the main reason behind the mild steel recommendation in the rule book. Most of the stuff run in LSR is amatuer built in a shed & most people can lay a successful weld on that but I have seen some pretty scary welds parked at Bonneville & when I say parked I mean the weld was parked on the metal!
  Sid. 

[Vinsky]

I agree with Pete on  the DoCol R, especially if you have little experience with CM. Downside is the cost.
http://www.ssab.us/globaldata/news-center/2016/01/18/08/06/racing-into-the-future-with-docol-tubing

[Interested Observer]

http://www.engineeringtoolbox.com/carbon-steel-pipes-standards-d_31.html
http://www.vallourec.com/onshorelinepipe/EN/E-Library/Publications/Lists/Publications/V_E00B0003B-GB.

[manta22]

Mild steel is a good choice. It is cheap, widely available, and it absorbs more energy due to its plastic deformation when stressed beyond its linear range.

4130N is commonly used in home-built aircraft construction but it is thinwall tubing and is oxy-acetylene torch welded in this application. This allows the joint to cool slowly and relieve stress.

Regards, Neil  Tucson, AZ

[Sumner]

Sumner, your article was a no show for me.... can you just post the link please 

Sorry, I think I got it fixed....

http://www.pirate4x4.com/tech/billavista/Links/

Sumner

[panic]

If your space permits, use the largest OD tubing that fits since stiffness (resistance to deformation and bending) varies roughly with the 4th power of the OD. 2" is 52% higher stiffness than 1-3/4" at the same wall thickness with only a 15% weight penalty.
The larger curve also makes gussets easier to fit tightly.