What grade of stainless steel does Bob's Muffler use in its exhaust systems, and why?

There are two primary categories of stainless steel tubing used in automotive exhaust systems: 300 series and 400 series. 400 series stainless is commonly used by Bob's Muffler for exhaust because it handles heat cycling better than the 300 series. 300 series stainless becomes brittle after constant heating and cooling (which is exactly what an exhaust system does) especially in areas that incorporate welds. The issue of heat cycling is of great importance, especially in a heavy-duty application that will endure greater levels of heat than other automotive applications. Not only is 300 series stainless a poorer choice for exhaust systems, it is also more expensive and would unnecessarily increase the price of an exhaust system. 400 series stainless is not as pretty as 300 series and will have a brownish hue to it, due to the fact that it has a higher carbon content than 300 series. This means the 300 series stainless will polish up better for appearance. The carbon content in 400 series also makes it magnetic, unlike 300 series, which is a simple test to determine which series you’re dealing with. Fortunately, 400 series will handle temperatures of up to 2000 degrees without any deterioration, making it very suitable for use in exhaust systems. At Bob's Muffler we offer both 300 series and 400 series stainless, for all our high performance mandrel bent exhaust systems.