The most common type of machinery used to bend exhaust pipes creates wrinkles in the pipe and it "necks down" or pinches the pipe partially in the bend area. This is the type of bends found on most exhaust systems. Of course, this restricts exhaust flow. Mandrel bends are made on special machinery using dies or guides that produce a smooth even diameter bend. High-performance aftermarket exhaust systems often use mandrel bends, but they are more costly to manufacture.

Keep a vehicle long enough and moisture from the exhaust gases will cause the system to rust and fail. Fortunately, many exhaust and muffler shops will provide a free inspection. They look not only at the condition of the pipes and mufflers, but also the hangers and mounts. Many exhaust system failures occur because one of the rubber hangers that isolate the exhaust pipes from the car body has broken. Then the exhaust system can flex excessively when the vehicle is driven, and this leads to failure of pipes and muffler connections. A quick visual inspection performed on your vehicle's exhaust system can identify necessary repairs when they can be done more economically and conveniently. Don't leave your vehicle's inspection till you hear that loud rumble and the grinding sound as part of your exhaust system drags on the ground.