Free had already developed a style of removing the seat from his mount, and lying flat prone along the back spine – thereby minimizing wind resistance, and placing most weight over the rear wheel. It is generally believed that this bike is The Black Lightning though, a custom order from the factory and was some 100 pounds lighter and 25 hp more powerful than the stock Black Shadow. In one of his books, Phil Irving (one of the designers) said that there were only about 16 of the model produced. The Black Lightning is the fastest Vincent ever produced.
To protect himself and allow comfort when in such a position, Free had developed special protective clothing. However, when his leathers tore from early runs at 147 mph (237 km/h), he discarded them and made a final attempt without jacket, pants, gloves, boots or helmet. Free lay flat on the motorcycle wearing only a
Speedo bathing suit, a shower cap, and a pair of borrowed sneakers – inspired by friend
Ed Kretz. This resulted not only in the record, but also one of the most famous photographs in motorcycling history, the "bathing suit bike" shot taken from a speeding car alongside his run on the Bonneville Salt Flats in Utah.