Michelin Put This Porsche 904 On Citroën Hydropneumatic Suspension And Used It To Test Tires For Decades

Porsche’s ludicrously beautiful 904 Carrera GTS is among the coolest race cars of all time. With a lightweight fiberglass body and a rev-happy gear-driven twin-cam flat-four engine, it was a real zinger on the race track and on hillclimbs in the mid-1960s. I’m an absolute dork for 904s, so when I saw this car — chassis number 904-034 — at the Le Mans Museum back in 2014 and snapped the terrible iPhone 6 photo you see below, I was instantly intrigued by its story. This car has lived in my brain rent-free for over a decade, and I think I finally have the full grasp of its story — and what a story it is!

The car was originally delivered to Herbert Müller in 1964, and was raced at the 24 Hours of Le Mans among other events, before it was sold to world-record cyclist Roger Rivière who wanted to get into racing. When Rivière eventually realized how dangerous racing was, he quickly sold the car. That’s where the story gets interesting, because it was purchased by famed French tire manufacturer Michelin. 

Once in Michelin’s care, the car was immediately shifted to tire test duty at the company’s Ladoux test center, itself brand new from 1963. Michelin determined that it needed a car which could test hundreds of different types and sizes of tires, including the strength of tire sidewalls under stress. As a way to increase stress on the sidewalls, the car was fitted with then-new Citroën DS hydropneumatic suspension in order to vary the ride height and modify the center of mass. 

By 1967 the car’s original Fuhrmann twin-cam engine had been put through the paces in racing and tire testing with who knows how many hard kilometers, and it decided to expire. Through the course of its hard three years on earth, it was damaged front and rear from crashes, and the engine was gone. Michelin set about putting the car right, or right enough that it could continue testing tires. The bodywork was fixed and the car was painted bright orange for safety reasons. The original 180-horsepower four-cylinder was yanked out and put under a tarp out behind the building, to be replaced by a then-new 1967 Porsche 911S flat-six engine, making the same 180 horsepower from the same two-liter displacement. 

I’ve reached out to Michelin a few times over the years to determine more about the car’s history, or perhaps uncover some period photographs of it in test livery, but they either don’t exist or are buried deep in the company archives and nobody cares enough to dig. It isn’t known how long the car was used for tire testing, or which tires it was used to test, but it seems the car may have seen action at the Michelin Engineering & Services test track deep into the 1980s before it was shelved. It was shoved into a garage somewhere and forgotten about until 2001 when an engineer uncovered the car and tracked down its Le Mans history. 

This rolling laboratory had served the tire company well, and had been discarded to the depths of cold storage. The engineer, who was from Le Mans, France, reached out to the Le Mans Museum to see if they might be interested. Between the engineer and the museum curator they were able to wrench the car, and its original blown-up engine, free of the giant corporation’s grasp. It was, by all measures, in seriously rough shape. 

With support from Michelin and oil company Motul, the car was given a full and extremely careful restoration back to how it looked when it first arrived at Michelin in 1965 or ’66. That original Furhmann four-cam engine, itself now valued deep into the six figures, had cylinders full of hazelnuts on teardown, evidence that a squirrel had made the engine its home at some point between 1967 and 2001. Given a sympathetic restoration the car is a rolling piece of weird history, blurring the line between race car and road car technology. This thing must have been an absolute hoot to drive in the ’70s with its bright orange paint, deep flat-six wail, and French-supplied adjustable suspension. I’m so glad it wasn’t left to rot in a warehouse somewhere, that thing belongs in a museum.