The hot days continue, but I’m still frequently driving my 964. Since it has Tiptronic, it’s easy to drive both around town and for commuting, making it arguably the best air-cooled Porsche for everyday use.

One day, I casually lifted the rear spoiler to take a look and found that the plastic bellows (accordion-style) part had deteriorated and developed holes. While it doesn’t directly affect driving performance, it looks bad from behind and isn’t ideal functionally, so I decided to replace it.

Porsche’s Rear Spoiler

Aerodynamics matter for cars that run on the Autobahn

The 911 has a rear that slopes downward, which isn’t great for downforce. Its cross-section resembles an airplane wing viewed from the side, so at high speeds, it actually generates lift instead of downforce.

A similar-shaped car is the first-generation Audi TT. Initially, it also produced significant lift, leading to many rollover accidents on the Autobahn due to insufficient downforce. As a result, a small rear spoiler was added in later minor facelift models.

This might not be a big issue in Japan, but in environments like the Autobahn, aerodynamics are very important.

Porsche 911 (964) catalog from the era

The 964’s Electric Rear Spoiler

From the 964 generation onward, the 911 is equipped with an electric rear spoiler that automatically raises at a certain speed (around 80 km/h for the 964).

This raised rear spoiler features a bellows-style expandable wall, so when viewed directly from behind, the lower part of the spoiler forms a black wall. This effectively channels incoming air into the engine bay to aid cooling, reportedly doubling the air intake.

However, if this wall has holes, the airflow simply escapes out the back.

Before and After Replacing the Rear Spoiler Wall

I asked my usual shop, Beeforce, to handle the replacement. It’s not like the driving feel changes dramatically, but having new parts just feels good.

Before replacement. The bellows were completely split open

After replacement

Since the rear spoiler is usually retracted, it’s easy to overlook issues here. If you own a 964, it’s a good idea to occasionally manually raise the rear spoiler and inspect it.