Step-By-Step Instructions On How To Flip A Tatra T87 at 20 MPH

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– Posted on March 25, 2021

The Lane Motor Museum in Nashville is my favorite one, and was the scene of our memorable 2016 CC Meet-Up. One of the main draws for me was their collection of Tatras, including this T87, seen here just about to land on its side. The Lane has a firm commitment to keeping all their cars fully driveable, and employees take home cars to keep them exercised.

A slightly more ambitious form of exercise was undertaken recently by journalist Sam Smith, on behalf of Hagerty Media. As part of their “Death Eaters” series, the T87 was driven 70 miles to Kentucky’s NCM Motorsports Park, where it was put through its paces to ascertain whether its reputation for tricky handling and “Nazi Killer” were justified.

It turns out it was, in the right hands and circumstances.

There was a preview: On the 70 mile drive to the track, cruising along at 70 or so, Smith encountered a buffet of wind from a passing semi. It sent the heavily loaded (63% of its weight) rear end stuffed with a 2.5 L hemi head air cooled V8 wagging back and forth, decidedly on its own volition. It eventually settled down, but Smith said it was the most disconcerting experience since 2015 when the Ferrari 488 he was track testing lost a wheel.

The moniker “Nazi Killer” is based on the story that Hitler forbade his top SS and Wehrmacht officers from driving the T87 because several were killed on high speed autobahn crashes. Who knows if it’s true; what is known is that Hitler and his officers were also in love with the big Tatras, and Hitler was adamant that his Volkswagen would “be like a Tatra”. Of course Porsche already had been working on a similar rear-engine concept for years, as described in my article “Who’s The Real Father of the Volkswagen”.  And true to form for any article on the Tatra and VW, Smith regurgitates the falsehoods that the VW was just a crib of the Tatra, as well as a few others. I should send him a link to my article.

It was well known that the first big rear engine Tatra, the T77, had serious handling issues, and that supposedly these were mitigated to some extent or another with the successor T87. But the combination of a V8 hanging out the back end and swing axles with skinny tires and a high roll center were still a recipe for disaster in the wrong circumstances or hands.

This is precisely why Porsche used the smallest, shortest and lightest engine possible in the VW, and insisted on an expensive magnesium case for the engine. He was determined to reduce the rear weight bias as much as possible, and it really did make a substantial difference. Of course VWs were rolled, invariably in the hands of drivers who didn’t know how to drive a rear engine oversteering car, meaning slow down before the curve and then keep on the gas going through it. And of course, the Corvair’s much heavier six cylinder engine exacerbated its snap oversteer issues.

The testing at the track went well enough, with Smith becoming familiar with the Tatra’s tail-out behavior in a wide range of speeds and turns. As Smith said:

The morning had gone well so far. I was interested, albeit wary, when the Tatra began to slide its rear tires in testing. The car was uniquely odd in a hundred ways but controllable, even predictable, once you learned its habits. We tried big slides and shorter ones, quick steps out and longer dramatic arcs, and the rear tires returned to grip either abruptly or gradually, depending on momentum and how much leash you were willing to give the helm. Above all, the engine’s mass and the rear suspension gave a domino effect in corners—once the Tatra’s substantial mass began moving in a given direction, the tail was following come hell or high water, even if the driver changed his mind. So long as you avoided trailed brake (the rear suspension would jack and hang) and kept your foot deep in the throttle (lifting in a corner transferred weight in a way that took acres of road to fix), the car seemed almost docile.

The rear tires were clearly being pushed hard, and that raises some questions. The T87 was of course originally conceived and sold with the bias-ply tires of the time. Bias ply tires are softer in the tread, but have a decidedly stiffer sidewall, or the inverse of radial ply tires. The T87 was shod with steel-belted Michelin X tires, a particular type that replicates as they were in the 1950s. It was known and understood that these had different characteristics than the bias ply tires.

The Tatra didn’t like gross attitude changes at any point, and it could seem recalcitrant, simply unwilling to shift mood once committed. As testing progressed, the rear axle’s behavior left us concerned about what would happen if one of the intensely stressed Michelins separated from the rim. After Lane personnel added five psi of pressure, I did a loop of the skidpad to feel things out.

 

The result was a shouting testament to how a vehicle’s suspension is the sum of its parts, and how engineers choose spring and damper rates to work with a given amount of grip. The added pressure allowed the tire to hold its shape more in corners, and the resultant added traction gave enough additional body roll that the Tatra’s inside wheel would hike a little and spin under power in corners. Emergency maneuvers were less consistent and made me more uncomfortable, so we proceeded with caution. The next run, when I went to initiate a gentle, first-gear spin—essentially a slide uncaught, no steering correction—the car went over.

And just what caused that?

It’s all here in this picture. Look at the outside rear tire: it’s practically popping off the rim. I don’t know if this shot was just before the flip or not, but this is the kiss of…a flip. And it’s exactly what Ralph Nader described in detail in his book “Unsafe At Any Speed” about the Corvair’s killer instincts. What happens is that as the rear end comes around, the swing axles tend to jack up, creating positive camber. The excessive forces on the outside rear wheel cause the tire to buckle under or even pop off the rim altogether, allowing the steel rim to contact the pavement.

As the rim digs into the pavement, any further sideways motion is stopped abruptly, so naturally the rear end of the car jacks up drastically and flips over. It’s the only and obvious outcome, thanks to the laws of physics.

And there is that inevitable outcome, from a tight corner taken at a mere 20 mph, which still involves considerable masses and centrifugal forces. More than enough to land the six-figure Tatra on its side.

Smith’s take on the tires:

The simple answer is that the lower pressure let the Michelins deform enough to approximate the behavior of bias-ply rubber. Regardless, when the outside wheel went into compression, the newly compressed axle acted as fulcrum. The car’s mass simply pivoted around it, and up she went.

I’m not sure I agree. Bias ply tires have significantly stiffer sidewalls, so relatively lower pressure on the Michelins (to approximate the behavior of bias ply tires) likely exacerbated the situation. The degree of tire deformation on that back wheel is shocking and surprising, given the low speed. I’m not speaking as a tire expert, but from what I’ve picked up over the years about the differences between bias and radials, and steel belted radials and fabric belted ones.

Back in the day when I had two VWs, I shod them with Semperit fabric-belted radials precisely because I had read on more than one occasion that the steel-belted Michelins were riskier to use on rear-engine cars because the stiffer steel belts caused a more abrupt break-away when its limits had been reached, exacerbating precisely the kind of behavior seen here by the T87. Semperits and Pirellis were common on VWs and Porsches, much more so than the Michelins of the times.  Those qualities of the Michelins undoubtedly improved over the decades.

The onlookers all pitched in to push the T87 back on its feet.

“It was a limousine,” Jeff Lane told me, after the rollover. He gave one of those what-can-you-do shrugs. “It’ll go around a corner faster than you think it should, but it wasn’t designed to be driven like this.” He’s not wrong. The unfortunate catch, of course, is that people did drive it like that, and a reputation solidified, and there you go.

And with that, testing continued.

So what did Smith prove? What everyone who has ever driven a T87 knows all too well: one needs to drive it with respect and consideration of its huge abilities as well as its foibles. And in the hands of those that respected that, it was a superbly comfortable car, highly capable under all manner of circumstances, including a 3½ year trip around the world in 1947 by Miroslav Zikmund and Jiří Hanzelka, two Czechoslovakians. Tatra supplied the T87, and they took it to the ends of the earth, literally.

Those that have experience with the T87 will tend to come down in two camps: they have either come to grips with its inherent limitations, respect them, but are comfortable with it. And there are those that have been terrified by it.

Swing axles were a milestone development, as they eliminated the huge unsprung weight of the heavy rear axles and hard springs of the times. Ride quality, especially over the generally rougher roads of the times, was greatly increased, and handling was too, as long as it didn’t involve V8 engines at the rear and the kind of maneuvers that provoked its bad habits. Ultimately, it comes down to knowing its characteristics and respecting them.

This is the same car when I shot it at the Lane in 2016. And undoubtedly by the next time I get back there, as soon as possible, it will be back to its pristine self. But it will have had some new experiences under its belt.

 

Hagerty Media article here  Images by Andrew Trahan

Related CC reading:

Automotive History: Who’s The True Father of the Volkswagen?

Automotive History: Hans Ledwinka’s Tatras