King of the Hammers prep season is officially in full swing, and Jason’s Polaris RZR build is coming together FAST. Built specifically for the Ultra4 4900 class at King of the Hammers 2025, this custom tube chassis RZR is being assembled with one goal in mind: survive the rocks, stay stable in the desert, and handle race-level abuse without compromise.
Developing the Chassis Around Real Racing
One of the biggest focuses during this stage of the build has been suspension development and driver packaging. Wide Open Design has been working directly with Radflo to test new internal bypass shock configurations and maximize front suspension clearance around the axle shafts and front chassis structure. The team installed temporary mounts and flex-tested the front suspension to provide Radflo with real-world numbers for:
- shock clearance
- front clevis positioning
- suspension travel
- and steering movement
Head Clearance Matters
One thing people often overlook on race builds is helmet and pumper clearance. Jason spent time mocking up helmet fitment, pumper routing, seating position, steering wheel placement, and roof clearance before finalizing the roof design. Modern race helmets now commonly place pumper ports on top of the helmet instead of the side, requiring additional overhead clearance in tight chassis builds.
37” OBOR Tires & Raceline Beadlocks
This RZR steps up to:
- 37” OBOR RocScraper tires
- Raceline beadlock wheels
- custom offset package
- lightweight race-ready wheel and tire combo
Jason specifically wanted to stay with a 15” wheel setup while maximizing ground clearance and top-end speed. Compared to previous chassis builds running 32s and 35s this setup pushes the chassis design even further while maintaining proper suspension and steering clearance. The end result is a wider, more stable platform capable of handling both desert speed and technical rock sections.
PRP Interior Setup
The PRP interior package on this build turned out killer. The car features:
- PRP Alpha seats
- PRP quick release steering hub
- PRP steering wheel
- PRP harnesses
- ratcheting harness system
The PRP ratcheting harnesses are a huge upgrade for racing because drivers can tighten themselves into the seat mid-race without stopping.
Combined with the containment-style PRP Alpha seats, this setup dramatically improves:
- driver stability
- control
- fatigue reduction
- and overall comfort during long race days.
Built for KOH 2025
This car still has a long list of final assembly items ahead:
- sway bars
- electrical systems
- dash layout
- GPS integration
- backup camera
- steering setup
- final suspension tuning
But the parts are arriving and the build is quickly transforming from a bare chassis into a true Ultra4 race machine. With:
- Radflo shocks
- Eibach springs
- OBOR tires
- Raceline wheels
- PRP interior
- Custom Splice recovery gear
- and a fully custom WOD chassis package
Jason’s latest creation is a testament to dedication, precision, and passion. Over the course of three years, he meticulously designed every aspect of this chassis in CAD, working through countless details to craft a rig that blends power, performance, and precision. In just under three months, using nothing but his weekends, Jason took his vision from the digital drawing board to reality, producing one of the most impressive Polaris Turbo R-based builds we’ve ever seen. Jason’s Polaris RZR is shaping up to be one serious contender for King of the Hammers 2025.
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