from casc regs:
The minimum size seamless or DOM tubing to be used shall be as follows:
Curb Weight Mild Steel Alloy Steel
Up to 1500 lbs 1.375” x 0.095” 1.375” x 0.080”
1501-2500 lbs 1.500” x 0.095” 1.375” x 0.095”
Over 2500 lbs 1.500” x 0.120” 1.500” x 0.095”
Or 1.750” x 0.095” ERW tubing may be used in the following sizes only.
Curb Weight ERW Tubing
Up to 2500 lbs 1.500” x 0.120”
Over 2500 lbs 1.750” x 0.120”
The minus tolerance for wall thickness shall not be more than 0.010” below
the nominal thickness.
see here for more detailed info:
http://casc.on.ca/uploadedFiles/2011_Ti ... 211751.pdf