As for the front windshield, this was kept stock for two reasons. First, while a Lexan front windshield would have saved about 16 lb, I wanted to keep the DOT safety glass for driving on city streets. The second reason was expense. A standard 911 glass windshield is about a third of the cost of a Lexan shield, which, after a season of running amidst a pack of racers with gummy tires, tends to be so badly pitted that it has to be replaced. The glass window holds up substantially better.
Another weight-saving piece, and one that aided greatly in streamlining the airflow over the car, was the flush rear window assembly from Performance Products. The 911's stock rear window does not rest flush with the roofline but is recessed beneath small slots used for ventilation. The flush-mount Plexiglass window utilizes a plastic frame installed in the area previously taken by the original glass and rubber seal. The frame is secured to the roof with aluminum rivets, and the flat Plexiglass replacement window is then fastened to the frame with 14 screws.
An added benefit is that the window can be easily removed for cleaning. This may sound trivial, but with the S's rear seat area fortified by a maze of rollcage bars, it would otherwise take a contortionist or a 3-year-old to slip through the labyrinth to clean the window.
Of course, even if a car is endowed with umpteen horsepower, feather lightness, exceptional agility and Hans Stuck behind the steering wheel, it means little if the tires do not adhere to the pavement. Okay, maybe it wouldn't matter so much if Stuck was actually behind the wheel, but he wasn't, I was, so choosing the correct rubber was critical for getting the most out of the 911S.
When I first purchased the car in 1978, it was running on Pirelli CN36 tires, which happened to be the tire company's first standard production steel radial and one of my all-time favorite tires. In its present form, the S required more than casual street shoes to keep it fused to the road. Thankfully, Pirelli is still a leader in tire technology for both high-performance and competition rubber.
For the track, a race car needs slicks. While tread design may determine the correct street or rally tire, with racing slicks the key is to choose the right tire compound to match the event's conditions, i.e., track surface, ambient temperature and the distance the race is scheduled to run.
As the project car was to be tested in mid-winter-albeit a California winter where the temperatures hover around 60F-the tire compounds suggested by the Pirelli technicians were a combination of their D5 and D6 tires.
The D6 compound requires less friction to reach its optimal temperature, and thus was assigned to the relatively light end of the car. In comparison, the D5 compound needs more input from the chassis and suspension to bring the rubber up to operating conditions. Obviously, a lot of friction is generated at the rear tire patch of a rear-engine car, so the D5 compound reached its preferred adhesiveness at the same rate as the front compound.