When Detroit Speed set out to build a new subframe their primary objective was to design and manufacture the ultimate performance subframe. The foremost structural components in a subframe are the framerails; therefore, much consideration went into the design of the rails. Numerous OEM and aftermarket technologies were considered until a fairly new manufacturing process called hydroforming was selected because of its considerable advantages over traditional manufacturing methods.

Hydroforming is a process in which malleable metals (steel, aluminum, etc.) are formed at room temperature into complex shapes using hydraulic pressure. This process produces high-strength, lightweight, dimensionally consistent, and structurally rigid components. Hydroforming enables the production of a single component that would otherwise be required to be made from multiple components joined together.

Each framerail of a Detroit Speed subframe starts out as a large piece of thin-walled carbon steel tubing. It is mandrel bent and
pre-formed into the general shape of the framerail. The tube is then placed inside a two-piece die whose internal shape matches that of the outside of the final framerail design. The ends of the tube are connected to a high-pressure hydraulic system. The tube is then formed into the shape of the die utilizing a specialized hydroforming process called Pressure Sequence Hydroforming. This process increases the formability of the material by using an initial low-pressure stage while the die is being closed followed by second high-pressure stage initiated after the die is fully closed. Unlike traditional high-pressure hydroforming, this method forms the part shape by forcing the tube to flow into the corner areas of the die without stretching or expanding the tube to fill the die cavity resulting in a formed part that has an average wall thickness equal to that of the starting tube. All of the forming operations are performed at room temperature which “cold works” the material thereby increasing its strength. Once the rail is fully formed it is removed from the die and trimmed with a 7-axis laser system resulting in a completed framerail.

The first widespread use of hydroforming in the manufacture of an automotive chassis was by General Motors for its full-sized 1999 Chevrolet and GMC truck lines. The Corvette C6 soon followed. Today, OE hydroformed chassis components are used industry wide.

Hydroforming has many advantages over original muscle car chassis manufacturing techniques, as well as “modern” replacement subframes constructed from standard steel tubing and multi-piece welded designs. The original Camaro/Firebird/Nova subframe rails were designed in the mid-1960s, using then state-of-the-art technology. Given the tire, suspension and manufacturing technology for the time, they were contemporary for their day; however, they are unable to match the performance of a current automotive chassis. A stock rail is composed of two separate pieces of stamped steel, which are stitch welded together. Hydroforming permits each rail to be made from single piece of steel that is ultimately stronger, lighter, and more rigid than the OEM design. Considerable weight savings are achieved by the use of thinner steel and through the elimination of the weld flanges, yet stiffness is greatly increased due to the exclusion of the discontinuous stitch welds. Welded, multi-piece replacement subframes suffer from many of the same issues as the original and often lack adequate strength and stiffness due to limitations presented by their fabricated construction.

Hydroformed rails are also far more precise than the original rails or multi-piece replacements. Since the same dies are always used for each set of rails, they are always consistent unlike jig-welded components. When dealing with suspensions, a mere sixteenth of an inch can mean a substantial difference when it comes to precise final alignment settings. In severe-use or
high-performance applications, such as autocross or track day events, precision alignment becomes even more crucial.     

Hydroformed framerails are more costly than a fabricated framerail. To justify the expense, Detroit Speed owner Kyle Tucker explained, ”When we were designing our subframe, we wanted to create the strongest, lightest, most structurally rigid component possible. Since we create our parts with the notion that pro-touring cars will see track duty or at the very least autocross use, performance was the main priority, not cost. With that being said, we needed a subframe that was going to allow us to optimize suspension settings and eliminate any structural deficiencies. We had to do that and keep in mind that there was a lot of weight we could eliminate over a stock subframe. Hydroforming was the only way to meet our goals, from a rigidity, weight and performance perspective. So far, the highest performance is what our customers have demanded for their cars, so we create products that satisfy their demands”.

Tucker added, “Hydroforming is a more costly process, but it is a contemporary technology. Being on the cutting edge is often a more expensive proposition, regardless of what the component is. Being on the cutting edge is what embodies a modern pro- touring car, though. We’re living in a world where the best of everything comes at a premium. Fortunately, we also live in a world where there’s room for everybody, so it’s all up to how someone wants to build his or her car.”