We tested the 2015 Polaris RZR S 900 on the rocks at Prairie City SVRA to determine how well its 60-inch chassis, short wheelbase and dual A-arm suspension worked in technical terrain. We also tested 30-inch tire clearance, adjusted the FOX Podium shocks and evaluated the RZR’s relatively tall low-range gearing. This test ultimately led to our RZR S 900 build for the 2015 King of the Hammers UTV race.
The original Polaris RZR S 800 always impressed us as a stock rock-crawling UTV. We even helped Jared Christie from Destination Polaris take one through the Rubicon Trail without any significant problems.
When Polaris replaced it with the 2015 Polaris RZR S 900, I was anxious to see whether the redesigned machine could improve upon the RZR S 800 in difficult rocks.
I had already driven the new RZR S at a Polaris media event in Utah, where it impressed me with more power, improved suspension and better ergonomics. Our complete Polaris RZR S 900 review covers its performance in the dunes, on faster trails and during the initial media ride.
We encountered a few rocky sections during that event, but I wanted to bring our demo unit home and test it on more demanding obstacles.
I should point out that my definition of rock crawling is probably more extreme than that of the average trail rider. I enjoy difficult trails in places such as Moab and the Rubicon, and I had already raced King of the Hammers several times. A completely stock RZR S 900 would be sufficient for many owners, but I wanted to see how far we could push the platform.
Protecting the RZR S 900 for the Rocks
The first step was protecting the RZR from rock damage. We installed the complete Factory UTV UHMW protection package for the RZR 900 platform, including a full skid plate, rock sliders and front and rear A-arm guards.
UHMW is an excellent material for this application because it is strong, resilient and slides across rocks instead of digging into them like some metal skid plates can. The full skid covered the belly of the machine, while the sliders protected the rocker panels and the A-arm guards helped shield the suspension.
Testing 30-Inch Tires on the RZR S 900
With the underside protected, the next goal was additional ground clearance. The quickest way to gain clearance under the chassis and suspension is to install taller tires.
The RZR S 900 came with 27-inch GBC Dirt Commander tires. The eight-ply Dirt Commander was already larger and more robust than the 26-inch Maxxis Bighorns used on the RZR S 800, but I wanted to find out whether the new machine could accommodate 30-inch tires.
Polaris representatives had told me that 28-inch tires would fit, but anything larger could interfere with the bodywork. Once home, I installed a set of 30-inch GBC Mongrels that had previously been used on my RZR XP 1000.
At the front, it appeared that a tire could contact the footwell when the suspension was compressed and the steering was near full lock. At the rear, the factory fender flare looked like the primary interference point.
Installing Narrower RZR 900 Fender Flares
I had noticed that the fender flares from the 50-inch RZR 900 had a much smaller footprint and would bolt directly onto the RZR S 900. I ordered a set from Placerville Polaris and installed them before testing the larger tires.
The smaller flares sacrificed some mud protection, but that was not a major concern for this build. Because the rear flares did not extend as far down or back, they created noticeably more tire clearance. The bodywork was also tucked closer to the machine, reducing the chance of clipping a flare against a rock.
The RZR S 900’s Tall Low Range
My biggest concern was the RZR S 900’s low-range gearing. Polaris made low range substantially taller on the redesigned RZR 900 platform. An RZR 800 would top out at approximately 25 mph in low range, while the RZR 900 could exceed 40 mph.
That made low range more versatile for many trail riders, but it was not ideal for technical rock crawling. A lower ratio provides better control, allows slower movement over obstacles and reduces the need to use the throttle and brakes against one another.
Rock-Crawling Test at Prairie City SVRA
With the underbody protected and the 30-inch tires mounted, I headed to Prairie City SVRA with my friend Paul Hart. Prairie City provided several useful rock obstacles along with a short-course track where we could jump the RZR, hit g-outs and check for tire interference under higher suspension loads.
We started in the rocks. The first thing we noticed was that the stock middle compression setting was too soft for this type of use. The RZR could move through its suspension travel quickly and drop the chassis onto a rock. Increasing compression damping on the FOX Podium shocks made a significant improvement.
The clutch engaged at approximately 1,750 rpm, and the RZR did not deliver as much torque at extremely low speed as I would have preferred. However, this was still a largely stock machine turning tires three inches taller than stock.
I deliberately placed the RZR in several awkward situations to evaluate its low-speed control and drivetrain. Despite the larger tires and tall low-range gearing, I never smelled the CVT belt. A lower overall ratio would have been better, but the RZR completed every obstacle we attempted. Some clutch tuning appeared likely to make the setup more manageable.
Electric power steering was particularly helpful in the rocks. The RZR S also felt much shorter and lighter than the RZR XP 1000. Its 79-inch wheelbase and 1,208-pound dry weight compared favorably with the XP 1000’s 90-inch wheelbase and approximately 1,379-pound dry weight.
Checking Tire Clearance on the Short-Course Track
After the rock test, we moved to Prairie City’s short-course track. The course, which had been used for VORRA and Nor Cal Rock Racing events, included jumps, corners and g-outs that could fully load the suspension.
We hit the jump near the start-finish line aggressively and did not see or feel any tire interference. The tires also cleared during g-outs and higher-speed cornering. The only potential contact we found all day occurred at near-full front suspension compression combined with substantial steering input.
Why the RZR S 900 Works Well in the Rocks
After a full day at Prairie City, I was impressed with the RZR S 900’s rock-crawling ability. Several characteristics made the platform particularly effective:
- Useful suspension travel without excessive width: At approximately 60 inches wide, the RZR S could fit through tighter lines than the 64-inch RZR XP 1000 while still providing 12.25 inches of front and 13.2 inches of rear suspension travel.
- Dual A-arm rear suspension: A trailing arm can strike a rock before the rear tire begins climbing it. The rear A-arms gave the RZR S 900 a cleaner path through many rock obstacles.
- Short wheelbase: The 79-inch wheelbase was approximately 11 inches shorter than that of the RZR XP 1000, producing a tighter turning radius and a more nimble feel. A short wheelbase can be a disadvantage on certain waterfall-style obstacles, but 79 inches proved to be a useful compromise.
- Relatively low weight: The RZR S 900 was more than 150 pounds lighter than the RZR XP 1000, helping it change direction and work through technical sections.
- Electric power steering: EPS reduced steering effort when the tires were loaded against rocks and made it easier to correct a line.
RZR S 900 Rock-Crawling Verdict
The 2015 Polaris RZR S 900 was a substantial improvement over the RZR S 800 for general trail use, and this test confirmed that it was also an effective rock crawler.
The 30-inch GBC Mongrels fit in nearly every situation after we installed the smaller RZR 900 fender flares. Increasing compression damping helped keep the chassis away from the rocks, while the UHMW protection allowed us to slide across obstacles without worrying about the underside.
The tall low-range gearing remained the machine’s principal weakness in technical terrain. I would have preferred a low range that delivered slower vehicle speed and more control, but the RZR completed everything we attempted without producing CVT belt odor. With appropriate clutch tuning, the gearing was workable.
From Prairie City to King of the Hammers
This test helped convince me that the RZR S 900 could become a competitive and entertaining King of the Hammers machine. Its narrow stance, short wheelbase and rear A-arm suspension were all valuable in the rocks, although the RZR XP 1000 retained an advantage in the faster desert sections.
We subsequently developed this same machine into our 2015 King of the Hammers RZR S 900 build. The upgrades included HCR Racing high-clearance replacement A-arms, which added strength, clearance and wheelbase without making the RZR wider.
The completed RZR S 900 went on to race at King of the Hammers. Read the complete 2015 King of the Hammers UTV race recap to see how the project performed in Johnson Valley.
