Back in the ’80s, BMW was the coolest brand in the world. It was putting out cars that were genuinely shocking the world and pushing boundaries in the best of ways. In the ’80s, BMW delivered the legendary E28 M5 and E30 M3, both of which were the first of their kind and both of which spawned entire segments for other brands to chase. However, BMW also debuted another car in the very late ’80s that’s less known but every bit as awesome — the BMW Z1.

The Z1 was a funky car then and it’s a funky car now. It debuted in 1988 and was the precursor to the BMW Z3 but its main party piece wasn’t its 2.5 liter inline-six cylinder engine or quirky styling. Instead, the BMW Z1 became famous for its sliding doors.

A simple press of the button next to the door activated the door mechanism. Once pressed, the window and door would slide downward into the lower sill. Admittedly, it still left a tall sill to step over, making ingress a bit tricky. However, it was one of the coolest door mechanisms ever made when it debuted. Once inside the car, you pull the typical ’80s BMW door pull once and both the door and window then rise back up.

The mechanism is actually rather interesting. It uses a motorized pulley system, with a toothed rubber belt that slides the door up and down and triggers the window regulator to work in tandem. In fact, the whole door mechanism operates like a window regulator. According to BMW Z1 forums, the doors work as such:

When the door button is pressed, (assuming window and door are closed)

A shaft behind the door button pulls a rod, Door motor and window motor are engaged, door and window opens together.
The rod releases the mechanical catch of the door, the catch activates the 1st step of the microswitch, instructing the door control unit “door is released”.
The second stage of the microswitch gives the ‘motor-on’ command to the door control unit, to start the motor (alternate up and down after initial setting).
The motor moves the belt and the door moves.
The window lifter is controlled by the door control unit. Except when opened manually, as the window motion is controlled by the manual movement of the door, incases such as flat battery, it is possible to open door and window by hand.

If door is open

When the button is pressed, the door motor lifts the door until it is closed (locked in the catch) and then the window motor engages to close the window.

If window is open

When button is pressed, only the door motor engages. If the window is partially open, it’s the same as if it is fully closed. Only difference is, that the window goes to its last known position when you close the door.

There’s also this helpful video, which shows the door working independently of the rest of the Z1. It’s really quite cool to see it work and it has such a smooth operation that it seems like it will work forever. Sadly, the BMW Z1 was very short lived and didn’t find a lot of buyers. However, the few BMW Z1 owners that exist are loyal, almost cult-like, followers of the funky little convertible and it’s not hard to see why.

This content was originally published here.