Poop Pipe Info!
OK, since I do work on my truck with pipe, thought I'd post a little info.
Pipe is Pipe and Tube is Tube, they are different.
Tube is measured by outside diameter and wall thickness.
Pipe is 'measured' by inside diameter and schedule (wall thickness)
However, pipe is still a standard OD, and the ID varies based on the schedule. So for a 1-1/4" pipe, the OD is 1.66". Schedule 80 would have a smaller ID than Schedule 40...etc..
There's a lot of misinfo about pipe, people thinking its brittle, weak, etc. Not really true. There are a lot of different types of pipe, just like there are lots of types of tube. So getting the right material, no matter what you do, is the key to getting strong material. You will find plenty of circle track cars with pipe-built roll cages, which are going to have higher impact forces than on most any 4x4.
There are lots of types of pipe out there. Going to the home depot and buying a 10 chunk of pipe you don't know what you are getting, and its propably crap. Some types of pipe might be butt welded, so there are butt seams in the pipe that may be weak. Some types might be a weaker iron that leads people to think of the pipes being brittle.
A common one used in building cages is ASTM A53 type S grade B.
This is a carbon steel pipe, with a yield strength of 35,000 psi, and tensile strength of 60,000 psi.
I personally use ASTM A500 grade B, which is a carbon steel pipe known as structural tubing. The A500 standard actually covers both rounds and shapes such as sqaure tubing, and is often what you are buying when you buy square & rectangle tube. It is known as tubing although the rounds are available in pipe sizes. It is specifically designed for use in structural applications, and not going to be brittle or weak like people think. Min yield strength is 42,000 psi, tensile strength is 58,000 psi.
For most roll bars, bumpers, sliders, etc, 1-1/4" schedule 40 makes a nice size. That is a 1.66" OD, with a wall thickness of 0.140". Currently, a 21 ft stick of A500b 1-1/4" sch 40 runs about $35 at Pontiac Steel.
I am using 2-1/2" sch 40 for my rear driveshaft, as well.