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I am planning on building a chassis car for E.T. and super class racing. I have a friend that races a chassis car with mild steel square tubing that is deadling consistent. My question is, which chassis will be the best: a round tube or square, mild steel or chrome moly? I want to make sure I get the best for my use and not to over-spend on something that I don't need. I understand that chrome moly round tube chassis is slighter than the mild steel one. Thanks, James: It is my opinion that mild steel should never be used for construction in any kind of race car especially drag racing. There a lot of stories out there that chromoly wears out quicker or that they flex more. The bottom line is that square tubing is much weaker because it has four flat sides to it which has no rigidity at all. Round tubing is much stronger than square tubing. When you talk about mild steel tubing, it is based on numbers as far as the hardness of the steel. Mild steel is usually 1018 but can range from 1010-1020. Chromoly is 4130 or 4140 and is just that much stronger. The higher the number the higher it is in tensile strength and the stiffer the material is. 4130 still remains flexible but not so rigid that it snaps. It has "memory" which mild steel does not. Mild steel tubing bends very easily so if it gets into a huge wheel stand problem it will bend and stay bent where 4130 has quite a bit of memory and it will flex, bend and come back to where it is supposed to be. So I definitely recommend 4130 in any kind of car. Mild steel has no place in a car, it's heavier and weaker; the only place we use mild steel tubing in our cars is making weight bars. When it comes to the cost, 4130 is just a little more money per foot, so the difference in a complete car is only a couple hundred dollars. In a chassis it winds up being lighter because you are able to use much thinner walls. All the tubes in a mild steel chassis have to be a minimum of .118" wall thickness by the regulations set by sanctioning bodies. Whereas with 4130 the thickest tube is .083" (the main cage) and you can go down to .058 and .049 on many of the tubes, so you save a lot of weight in the wall thickness alone. |
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Rick: