Shock Therapy is one of the many aftermarket companies in Arizona specializing in modifying UTVs for dunes, desert and short-course racing. The Shock Therapy crew has more than 25 years of off-road racing experience with Trophy Trucks and Class 1 buggies, and when more and more race teams started using UTVs for pre-running, they started re-valving and -springing Rhinos, Teryxs, RZRs, Mavericks and Wildcats for a plush ride at speed. Now, ST is a premier suspension-tuning company that holds several patents, and their Polaris RZR XP 4 1100 and XP Turbo are rolling test beds for developing new products like the XP frame supports, silent cross-over rings and the brand-new triple bypass system. The XP 4 build also has support from Weller Racing, DragonFire Racing, TMW Off-Road, BS Sand Seats, LoneStar Racing, RCV Performance, Wolf Designs, Sin-Fab, Trinity Racing, Sand Tires Unlimited, DWT, Baja Designs, Rugged Radios, 5150 and ATVonics; many are based in Arizona.
WELLER RACING POWER
Weller Racing provides the power with its WR Stage 5 big-bore kit ($3,299.99), which includes two 96mm forged piston kits, bored and plated cylinders, CNC porting and polishing, +1mm valves, head studs, valve-bucket kit, dual valve springs with Ti retainers, adjustable shim kit, WR-profiled cams, automatic timing-chain tensioner, new OEM oil filter, spark plugs and gasket kit including valve seals. This kit bumps rear-wheel horsepower from 84 to 95-plus horsepower. The CVT is upgraded with Weller’s Kyle Tuned clutch kit ($389.99) with modified helix, springs and adjustable weights, and the transmission is armed with WR heavy-duty bearings. RCV Performance Pro II Series axles ($725 each) beef up the drivetrain for the extra power and stress of turning 31-inch Sand Tires Unlimited Tribute front and Blackbird rear paddle tires. RCVs have a 33-spline 300M shaft and 4340 chromoly CV bodies, with the inner CV plunging 2.25 inches. Sinister Fabrications arms the rear end with 5/8-inch radius rods ($489.99).
TMW & DFR OFF-ROAD STYLE
TMW’s XP 4 Venom cage starts at $1899, with MIG welding, 0.95-inch DOM tubing and extra support tubes, and powdercoating and an aluminum roof add $780. XP 4 full doors by TMW are $1350, plus graphics, but ST went with a full Extreme Plus Wrap by Wolf Designs ($480). BS Sand supplied four Extreme full-suspension seats, and they were fitted with DFR 3-inch, 5-point harnesses ($139.99 each). DFR also supplied the Sport V steering wheel with a quick-disconnect kit ($281.99), and TMW also fitted its Venom cage with a glass windshield and rear-view mirror.
LED lighting is a must for night riding, and the stock RZR headlights were replaced with Baja Designs’ Sportsmen XP1K headlight kit ($584.95), which includes four Squadron Sports LED cubes (two spot and two combo at 1800 lumens each), mounting brackets and plug-and-play adapters. Sinister Fabrication’s XP1K front grill with a 10-inch, 30-watt LED is $199.99, and Sin-Fab’s Totron 40-inch combo LED light bar is $299.99 and puts out 9600 lumens. The 5150 LED whips have built-in three-button controllers, in-line fuses and quick-release mounts; their 6-foot color-changing LED whips are $325 for two.
Rugged Radios’ Dune Rider 25-watt car-to-car radio and four-person intercom system (RRP660) is $1,259.90; the RM-25R radio has 200 programmable channels and 40 pre-programmed off-road channels, and the RRP660 intercom has Vox control for loud environments, music in with auto muting and an iPhone connect port. ST also added Dunertunes’ five-speaker audio system with JL Audio speakers; this Phoenix-based company is no longer in business.
RIDE BY SHOCK THERAPY
This XP 4 has LoneStar Racing’s factory-length front A-arm kit ($1550), and the Walker Evans Racing (WER) 2.5-inch front and 3.0 rear shocks are Stage 4, including Ride Improvement System valving ($749.95), dual-rate spring kit with silent cross-overs ($895.95), and a front torsion bar kit ($649.95) and ST rear torsion bar ($549.95). The XP 4 also gets frame supports ($199.99), billet rear torsion-bar links ($149.95) and steel shock bodies ($125 each). If you move the aluminum preload ring on the OEM aluminum shock body, it galls and seizes, so ST machines steel bodies to eliminate that chance. Between the RIS, DRS and ST torsion bars, your XP or XP 4 will float like a hovercraft over the nastiest chop yet track like it’s on rails, but ST has more tricks in the works.
TRIPLE BYPASS SURGERY
Shock Therapy is working with Walker Evans Racing (WER) on Internal ByPass (IBP) shocks for RZR XPs. Shock Therapy’s IBP shocks work in conjunction with the OEM WER needle shocks that are modified with lighter valving and spring rates, and they mount behind the rear shocks with bolt-on bottom and clamp-on top mounts. The IBP shocks have three external tubes—two for compression and one for rebound—to provide a plush ride in the small stuff and eliminate bottoming on big dune jumps. The triple-tube design provides four stages of travel, and finger and wrench adjusters on the external tubes control when each stage engages.
Basically, small chop is handled by the coil-over shocks only, as the lowest tube on the IBPs displaces fluid for no damping. Get into whoops and the coil-overs control the first half and the IBPs control the second half of damping. When the IBP pistons pass the top of the first and second tubes, those sections increase damping forces, and the last stage firms up more to prevent bottoming. On big jumps and dune G-outs, which fool speed-sensitive damping, the IBPs do all of the damping work. Once dialed in, the Shock Therapy IBPs provide a plush ride with no bottoming, whether there’s only the driver in the RZR or three passengers and the driver in an XP 4. MSRP will be $2,695.95 for WER-shocked RZR XPs only. Fox Editions require reservoir mounts, and Turbos will need CVT duct reroutes.
With the IBP kit, lifting for big whoops and tabletops on Sand Highway will be a thing of the past.
2609 N. 35th Ave.
Phoenix, AZ 85009
3191 N. Washington St, Suite 2
Chandler, AZ 85225
P.O. Box 116
Wittman, AZ 85361
2010 W. Parkside Lane #122
Phoenix, AZ 85027
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Mesa, AZ 85210
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