EV1 engineers developed an amazingly solid aluminum structure in which all of its elements are bonded together into a single rigid unit. With a stiffness rating of 25 Hertz, the EV1's structure is one of the simplest, lightest, stiffest structures for any vehicle of its size in the world. This structure, combined with electric propulsion and polymer exterior panels, creates a durable car that is designed to have a long life.For obvious reasons, this platform had to be as light as it is stable. After all, this is a car program that measured its success in grams. Any extra weight — no matter how minute — meant a loss in range to the driver. And that was simply not an option. The suspension system is another lesson in lightweight materials. The suspension system was designed under the watchful eye of engineers like Clive Roberts, a former Lotus suspension engineer who was on loan to the electric car program and is now a GM lead development engineer. The design artistry of the suspension system is especially smart when you consider the challenge faced by EV1 designers: To develop new front and rear suspensions that would work with 50 psi tires. These higher-pressure tires, compared to the 30-35 psi found in normal all-season tires, presented a real challenge for Clive and the design engineers. In the front, they chose a short/long arm variation on a double-wishbone design with forged aluminum components that reduce weight and isolate the driver from road shocks while increasing handling ability. In the rear, they chose an aluminum beam axle, micro-alloy steel springs and links of strong fiberglass rods with aluminum die-castings bonded to each end. Not surprisingly, the result is a car that rides very well and handles like a sports car.