Our 2018 Polaris RZR XP Turbo Dynamix Edition had already shown its range in faster terrain. The question for this test was whether its electronically controlled FOX shocks could help on the slow, punishing rock trails of Johnson Valley, California, home of King of the Hammers. After several days on trails used in the race, FIRM mode delivered a useful surprise: more ride height and better support when dropping off ledges. The stock low-range gearing remained the limiting factor.
We had previously taken a 2016 RZR XP Turbo rock crawling on the Barrett Lake Jeep Trail. For 2018, the XP Turbo made a claimed 168 hp and gained the DYNAMIX active suspension option. Our RZR XP Turbo Dynamix first ride review covers the system in faster terrain; this test focuses on its behavior in the rocks.
What DYNAMIX FIRM Mode Does in the Rocks
The 2018 system monitors vehicle inputs and adjusts shock compression damping on the fly. The dashboard switch also lets the driver choose COMFORT, SPORT or FIRM. COMFORT provides the softest baseline, SPORT adds support for faster driving, and FIRM commands maximum compression damping.
On our equipped test RZR, selecting FIRM made the shocks resist compression enough to raise the vehicle roughly two inches compared with its softer setting. That was an observed change in ride height during our test, not a mechanical lift or a promise of a fixed two-inch clearance gain on every RZR. In Johnson Valley, the extra underbody room helped when picking a line over ledges. I could switch back to COMFORT or SPORT when the trail opened up.
How We Equipped the 2018 RZR XP Turbo Dynamix
This was a modified test vehicle set up for severe rock trails and potential King of the Hammers use. Its performance should not be mistaken for a stock-machine test. The build included:
- Cognito Motorsports stock-width A-arms, trailing arms, radius links and tie rods, plus a Cognito cage, doors and tire carrier.
- Shock Therapy dual-rate springs and Ride Improvement System.
- 15 × 5.5-inch Walker Evans Racing Forged Legend beadlock wheels, BFGoodrich 32 × 9.50R15 tires and Walker Evans Racing Walker Links.
- RCV Pro Series II axles and Zollinger Race Products billet hubs.
- Factory UTV UHMW skid plate, rock sliders and A-arm guards; a Warn 9.0rc winch in a Campbell Enterprises bumper.
- KC HiLiTES FLEX LEDs and rear tail light bar; XTC Power Products power control and turn signal systems; Sick Stick LED whips.
- Rugged Radios intercom, radio and helmet blower; Magellan TRX7 GPS.
- Momo steering wheel, Simpson Vortex Rally suspension seats with D2 3 × 3 harnesses, and a BlueFire Outdoors gated shifter.
Johnson Valley Trail Test: Clearance and Articulation
We spent several days on Johnson Valley trails that had been part of the King of the Hammers UTV race. I drove the car as I would on a race pre-run, with plenty of challenging ledges and rock transitions. FIRM made the suspension stiffer, but the ride was less punishing than I had expected. It held the chassis up over obstacles and resisted blowing through the shock stroke when the RZR came down off a rock.
There was a trade-off. With the shocks resisting compression, the front end did not articulate as freely. On Turkey Claw, disconnecting the front sway bar improved front-wheel movement considerably. That observation applies to this setup and trail; a disconnected sway bar also changes handling, so reconnect it before faster driving.
The video shows the RZR working through the rocks with the front sway bar disconnected:
The Limitation: Stock Low-Range Gearing
The XP Turbo’s low range felt too tall for slow, deliberate crawling. In race-style driving, where I could maintain more momentum, it was manageable. On technical obstacles, I sometimes smelled the CVT belt and had to change my approach speed. We did not break a belt during this test, but FIRM mode could not solve a gearing and clutch-load problem.
That made me appreciate the lower gearing in the 2017 RZR XP 1000 Gold Matte Metallic Limited Edition that I raced at King of the Hammers in 2017. Its low range was reported as 55 percent lower than a standard RZR XP 1000’s, yet it could still run around 30 mph in low. The Turbo brought far more power and, in this Dynamix build, useful ride-height control; the naturally aspirated rock-focused RZR had the gearing I wanted on slow climbs.
Verdict
For our modified 2018 RZR XP Turbo Dynamix, FIRM mode was genuinely useful at Johnson Valley. It kept the chassis higher over rocks and helped prevent harsh bottoming on ledge drops. The added damping restricted articulation, which the front sway-bar disconnect helped address. If I were choosing a King of the Hammers RZR from those available at the time, I would have wanted this Turbo’s power and shock control combined with the Gold Matte Metallic Limited Edition’s much lower crawl ratio.
For another perspective on the platform in the rocks, read our RZR XP Turbo S rock crawling review and the later lower gearing test on our Turbo S.
