By Cody Hooper. Photos by Robert Utendorfer.
Building a competitive desert-racing UTV requires much more than installing a cage, shocks and larger tires. Holz Racing Products demonstrated that with its No. 1964 Polaris RZR XP 1000, a purpose-built race vehicle developed for the punishing conditions of the Best in the Desert series.
Although the finished machine remained recognizable as a Polaris RZR XP 1000, Holz stripped the vehicle to its frame and rebuilt nearly every major system around durability, safety and serviceability. The result provides an excellent look at how professional UTV desert race cars were being developed during the middle of the 2010s.
These competition machines helped establish the RZR as one of desert racing’s dominant platforms. For more background on that progression, see our history of the Polaris RZR and Polaris RZR Factory Racing history.
Building a Best in the Desert RZR XP 1000
Desert racing exposes a vehicle to relentless impacts, heat, vibration and component fatigue. A machine that feels strong during a recreational ride can quickly find its limits when driven at race speed for hundreds of miles.
Holz Racing Products approached the No. 1964 build with years of UTV racing and fabrication experience. Instead of concentrating solely on horsepower, the team focused on creating a balanced race car capable of maintaining speed without overstressing its chassis, suspension or drivetrain.
The 1900-series class rules in effect when this vehicle was built required a production-based UTV with a stock bottom end and cylinder head, production chassis dimensions and suspension mounting locations, one shock per corner and tires no larger than 30 inches. Maximum width was limited to 70 inches.
Those historical rules shaped nearly every part of the No. 1964 build. Holz had to improve strength, cooling and handling while retaining the production-based components required by the class.
Reinforced Chassis and Race Cage
Holz began with a new Polaris RZR XP 1000 and disassembled it to the frame. After removing the factory coating, the team reinforced high-stress areas of the chassis, including the upper A-arm towers and other suspension mounting points.
A fully welded 4130 chromoly cage replaced the stock structure. Custom aluminum panels, firewalls and protective covers helped isolate the occupants while protecting important mechanical components from rocks, debris and heat.
From the outside, the vehicle still looked like an XP 1000. Underneath the bodywork, however, it had been comprehensively prepared for the sustained punishment of desert competition.
Holz Suspension and Walker Evans Shocks
Holz manufactured a custom suspension system that widened the RZR by two inches and increased its wheelbase by three inches. Rather than pursuing the largest possible suspension-travel number, the team worked within a range that protected the shocks, CV joints and axles from excessive operating angles and loads.
Walker Evans Racing supplied adjustable 2.5-inch VS2 shocks with large reservoirs and Eibach springs. The unusual reservoir position placed the compression and rebound circuits closer to the center of the shock body, reducing the distance oil had to travel through the adjustment circuits.
The setup was designed to absorb repeated high-speed impacts while preserving control through rough desert terrain. Fine adjustment also allowed Holz to tune the car for different courses, loads and surface conditions.
Race-Prepared Drivetrain and Steering
Class rules required Holz to retain several original Polaris components. The team modified the production CV joints, transmission and clutches for greater durability and improved cooling while staying within the regulations.
Summers Brothers 300M axles replaced the stock axles. A Howe steering rack, modified by Holz, worked with the factory Polaris electric power steering system to improve steering durability during long desert races.
The car rode on 15-inch Walker Evans Racing beadlock wheels and 30x10R15 BFGoodrich KR2 race tires. The tire size satisfied the period’s class limit while the race-specific construction provided the traction and puncture resistance needed in rocky desert terrain.
Purpose-Built Racing Interior
The stock cockpit was replaced with a functional racing interior built around safety, navigation and vehicle monitoring. Sparco carbon-fiber seats and Impact Racing restraints secured the driver and navigator, while a Sparco steering wheel mounted to a Holz quick-release hub.
A Lowrance HDS7 GPS sat in front of the navigator for course mapping and navigation. The custom aluminum dashboard housed the factory Polaris instruments, AutoMeter gauges and Blue Sea Systems switches.
Rugged Radios supplied the radio and intercom system, allowing the occupants to communicate with each other and the team. Helmet blowers helped manage heat and dust during long races.
Dry-Sump Engine and Upgraded Cooling
The Polaris ProStar 1000 engine retained its production-based architecture but received a Holz dry-sump oiling system with increased oil capacity. A Setrab auxiliary oil cooler was mounted above the rear bedside to help control engine-oil temperature.
A large Ron Davis radiator and electric fan were positioned behind the occupants near the center of the vehicle. Relocating the radiator helped protect it from damage while allowing it to draw relatively clean air through the open windshield area.
The exhaust system combined the stock Polaris header with an SLP muffler. Holz also added cooling for the transmission, addressing another potential source of heat during sustained high-speed competition.
Minimal Lighting and Controlled Weight
Vision X supplied the race lighting. Instead of surrounding the vehicle with numerous LED bars, Holz used a relatively minimal lighting package that provided the required nighttime visibility without adding unnecessary weight.
That philosophy extended throughout the build. Every component had to contribute to safety, reliability or performance. Keeping weight under control reduced suspension and drivetrain loads while helping the vehicle accelerate, brake and change direction more effectively.
Early Race Performance
The No. 1964 made its early competition appearance at Nevada’s Silver State 300 after only one full day of testing. Mark Holz and his son Ryan reportedly built a six-minute lead before a cam-chain tensioner failed at race mile 206.
The mechanical failure ended the race, but the car’s pace demonstrated the potential of the new chassis and suspension package. It also illustrated a central truth of desert racing: outright speed only matters if the vehicle reaches the finish.
Holz Racing Products applied many of the lessons learned through competition to suspension, chassis and race components offered to recreational drivers and other racers.
Holz Racing RZR XP 1000 Build Specifications
- Base vehicle: Polaris RZR XP 1000
- Race number: 1964
- Chassis: Custom 4130 chromoly fabrication by Holz Racing Products
- Body and sheet metal: Custom fabricated by Holz Racing Products
- Suspension: Holz Racing +2-inch width and +3-inch wheelbase system
- Shocks: Walker Evans Racing 2.5-inch VS2
- Springs: Eibach
- CV joints: Production Polaris components modified by Holz Racing
- Axles: Summers Brothers 300M
- Wheels: 15-inch Walker Evans Racing beadlocks
- Tires: 30x10R15 BFGoodrich KR2 race tires
- Steering rack: Howe, modified by Holz Racing
- Power steering: Polaris EPS
- Steering wheel: Sparco with Holz Racing quick-release hub
- Seats: Sparco carbon fiber
- Restraints: Impact Racing
- Gauges: Polaris and AutoMeter
- Switches: Blue Sea Systems
- Lighting: Vision X
- Fuel cell: Fuel Safe unit by Holz Racing
- Brakes: Streamline oversized rotors with Holz caliper mounts
- Spindles: Heat-treated 4130 chromoly Holz Racing spindles
- Front differential: Production Polaris
- Transmission: Production Polaris transmission modified by Holz Racing
- Transmission cooler: Xtreme Plus and Holz Racing
- Clutches: Production Polaris clutches modified by Holz Racing
- Engine: Polaris ProStar 1000 with Holz dry-sump system
- Exhaust: Production Polaris header with SLP muffler
- Radio and intercom: Rugged Radios
- GPS: Lowrance HDS7 PCI
- Helmet fans: Custom Holz Racing
- Radiator: Ron Davis
- Oil cooler: Setrab and Holz Racing
- Powder coating: Advanced Powder Coating
- Graphics: Utendorfer Graphic Design Service
- Wrap: SSI Graphics
Editor’s note: The class descriptions and component specifications above document the vehicle and Best in the Desert regulations from the period in which this race car was built. Current racers should consult the latest sanctioning-body rulebook before preparing a vehicle for competition.
