Via: speedracer wiki
"In the American West, a convoy of trucks is crossing the desert. A group of motorcycles scream down the mountainside and attack the convoy.
Meanwhile, Speed wins the Southwest Grand Prix. One of Speed's fans is admiring the Mach Five when Speed walks into the garage. He says that he wanted to be a professional racer himself but didn't make it. He doesn't give his name.
That evening, Speed and the gang are dining with Mr. Skyhigh from the Office of Space Development. Later, in a ghost town Skyhigh is trying to enlist Speed's help to protect the construction of an international space development base. The crews and equipment are being attacked by motorcycle Apaches. The Mach Five is needed to transport a shipment of uraniumtane, an element that will give nuclear missiles an explosive power greater than an H-bomb."