From Off-Road to Race Track: The Pro-Street RZR

Wyoming is a tranquil little town in the US state of Minnesota, surrounded by lakes, forests, and grassland–and is thus an ideal location for the development department of Polaris, a world-renowned manufacturer of off-road vehicles. Engineers can test four-wheeled off-road buggies like the RZR right next to their offices. The compact, high-legged two-seater with its striking front end has been a notable presence on the off-road scene for years. But in the summer of 2019, there was something unexpected to marvel at during a major dealer show at the company headquarters: the road version “Pro-Street RZR”, developed and built by the experts at Porsche Engineering in just four months.

Brian Gillingham
Chief Engineer at Polaris

The idea for the racetrack version of the RZR came to the engineers at Porsche Engineering during a joint project to optimize the chassis and handling of a Polaris off-roader set to be launched in 2021. “We had the idea of transferring the potential of the RZR to the racetrack,” says Marc Kluge, Senior Manager Design Drivetrain at Porsche Engineering. After all, the RZR variant offered him and his employees the opportunity to demonstrate the overall vehicle know-how of Porsche Engineering while incorporating experience from sports car development. “The Pro-Street RZR shows that we always look at and understand the vehicle as whole.” This includes chassis development as well as our knowledge of the vehicle body and the finer points of the individual components,” says Kluge. “It also gave us the opportunity to show Polaris that Porsche Engineering also builds complete demo vehicles on request.”

Polaris Chief Engineer Brian Gillingham, like his colleagues, was enthusiastic about working with Porsche Engineering from the very beginning. “We sensed immediately that two very similar corporate cultures were at work here: enthusiasm for the technology, courage to try things out and think laterally, direct lines of communication in implementation. It clicked right away.” Without hesitation, he says, they trusted that the idea was feasible—and gave the engineers at Porsche Engineering great freedom to achieve their goal.

Their self-appointed task, in turn, was clear: it was not intended to be a completely new development, but a variant based on the existing off-roader. “We wanted to use as many identical parts as possible and modify the original vehicle skeleton only minimally,” says Kluge. Vehicle parts such as the dashboard, the drivetrain and the body panels were already available as “carry-over parts” (COP). Using them was key to enabling rapid implementation of the project.

The result is impressive. “You can still see the Pro-Street RZR's origins, but at the same time its purist design makes it an absolutely track-ready race car,” says Kluge. Indeed: the striking front end has remained the same. Only the bumper that normally adorns the off-road version is missing. The Porsche Engineering team also left out a large part of the paneling. This saves weight and provides a clear view of the chassis and engine. The driver’s cage was also changed: the Pro-Street RZR has a new, lower rollbar. The two passengers sit in a flatter cage without a roof or windshield, made of the same material as the rollcages of Porsche race cars. This changes the overall silhouette, as does the wide and high-mounted rear spoiler.

But the most striking change is the new road position. While the high-stepping original RZR offers a ground clearance of more than 30 centimeters, the road version glides only a few centimeters above the asphalt—as befits a race car. In this, among other aspects, the engineers from Porsche Engineering were able to bring their motor racing experience to bear: new suspension struts with an optimized angle bring the vehicle closer to the road. Together with specially tuned dampers, a modified wishbone geometry, new stabilizers, and 18-inch rims, they give the vehicle a wider track. This generates greater handling stability and also matches the special conditions of race tracks: less vertical forces than off-road, but higher lateral forces when cornering at speed. And of course, the Pro-Street RZR does not utilize high-profile off-road tires, but racing tires selected on the test bench. “This is another example of how we have optimized the entire vehicle for the racetrack down to the last detail,” says Kluge.

The low road position did require further modification, however. Normally the tank of the RZR is mounted under the seats. Since there was no room there, it was installed on the rear frame. Carbon shell seats and high-performance brakes further heighten the sports car character of the Pro-Street RZR. “The powerful brakes are needed to cope with the higher deceleration and the associated high energy input to the brakes,” explains Kluge. The steering was also adapted to racing conditions. Instead of using power steering, the driver steers purely mechanically. “This gives more direct feedback and ensures more precise handling, as is needed on the race track,” explains Kluge. The engine and automatic transmission remained unchanged, however. The two-cylinder engine with just under one liter of displacement and around 170 hp accelerates the Pro-Street RZR to around 160 km/h.

A team of eight colleagues at the Bietigheim and Mönsheim locations developed, calculated, and designed the RZR derivative over three months. After that, five Porsche Engineering employees assembled the demo vehicle in four weeks and tested it on site. In July 2019, the variant finally arrived in America by plane—and caused quite a stir there, as Gillingham recalls: “Our marketing manager personally broke open the shipping crate. And when the Pro-Street RZR was rolled out, we were all thrilled.”

Gillingham has had the opportunity to drive the variant himself. “My first thought was: it’s so low!” Of course the driving experience is completely different than the off-road version—not least because of the lower seat position, which leads to a different view of the road. A real race car feeling—for Brian Gillingham, the Pro-Street RZR is quite simply “cool.”

Among the visitors at the dealer show in Wyoming, the presentation of the Pro-Street RZR caused more than just astonished looks. “People were very interested and curious,” Gillingham recalls. “They found the vehicle truly fascinating.” And with that, Polaris had accomplished its goal. “Although we will continue to operate primarily in the off-road sector, we have shown that there is a lot more to Polaris when it comes to exciting technology,” says Gillingham. And the Pro-Street RZR will continue to be used as an attention-getter at corporate events.

Porsche Engineering is just as pleased with the result. “The Pro-Street RZR is fully track-ready and offers extremely agile and precise handling at a low weight—just as we had envisioned,” says project manager Kluge. At no point in time was there any doubt as to its feasibility. “A great and highly motivated team that had a lot of fun in the project has proven unequivocally: it definitely works!”

Text first published in the Porsche Engineering Magazine, issue 1/2021.

Text: Jost Burger
Contributor: Marc Kluge
Photos: Eduard Herr

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