At the first rounds of the 2020 Lucas Oil Off-Road Race Series (LOORRS) at Glen Helen Raceway, we patrolled the pits and UTV tech inspection and were immediately drawn to Myles Cheek’s HRP/CMI/WER RZR RS1 . The Holz Racing CMI Precision RS1 is loaded with trick products and innovative details; eye candy is everywhere on this RS1. Cheek went on to dominate the Pro Stock 1000-class qualifier and the first-round main, and he has won three of the five mains run at press time to lead the Production 1000 points over former champ Brock Heger by 13. Here is the scoop on Myles Cheek’s HRP/CMI/WER RZR RS1.

Polaris Factory Racing pilot Myles Cheek has a new ride for the 2020 Lucas Oil Off-Road Racing Series Nationals, a Holz Racing/Walker Evans Racing/CMI RZR RS1 that has won three out of five Pro Stock mains and finished second in the other two.


Chuck Cheek is Myles’ dad and owner of CMI Precision Machining. He and Jaime Campbell of Raceco did the build, starting with a Holz Racing Products (HRP) RS1 Race cage. The HRP Race cage is constructed of 1.75-inch 4130 chromoly steel tubes that are Tig-welded with triangulation to meet LOORRS race rules. The $4500 HRP RS1 cage includes an aluminum roof, full doors, number plates, firewall, dash, lowered seat mount, ECU mount, display hold-down and window nets. Chuck made his own firewall and an even lower seat base for Myles, giving the car a really low center of gravity for quicker handling. The bed delete even has a custom, billet-aluminum cross-brace for the cage downtubes.

CMI Precision Machining built the RS1 exhaust, along with the axles and radius rods for the Pro Stock points-leading #957 RS1. WER Velocity 2.5 shocks are custom-tuned for short-course racing.

Such a low seat meant having to move the OEM fuel cell, so Cheek scrapped it and made a custom CMI fuel cell that sits atop the RS1’s turbo-grade front diff. Side frame rails add strength to the RS1 frame and protection for Myles. Chuck fabricated a really trick engine-oil cooler with two fans and an engine breather to mount behind the firewall. A CBR radiator sits behind Myles. CMI also machined the adjustable radius rods, bearing carriers, billet hubs ($243.95) and big-rotor brakes with light-weight caliper brackets and guards. The beautiful, three-piece RS1 wheels are also CMI, shod with Hoosier 27.5×8.0-15 Chain-Link UTV race tires with the M500 compound, and they’re armed with Tire Balls.

The Walker Velocity 2.5 shocks are protected by Ebbco carbon-fiber shock guards, and the HRP suspension and front and rear torsion bars add rigidity, precision and handling to the RS1. CMI axles and hubs add strength, too.

HRP’s Heavy-Duty Race A-arm kit ($1600) improves strength with 0.95-inch, 4130, heat-treated alloy tubes with Teflon bushings and heavy-duty FK brand Uni-Ball-type ball joints. They’re mated with Walker Evans Racing Velocity 2.Five Series racing shocks and an HRP front torsion bar and bumper ($749.95). Out back, HRP’s H-D trailing arms ($1600) shave 8 pounds of weight while adding strength and stiffness. They have 4130 chromoly steel construction with internal gussets and OEM shock, sway-bar and bearing-carrier mounts. They’re powdercoated black and mated with HRP’s trailing-arm guard flaps ($125) and HRP’s adjustable rear torsion bar kit ($499.95). The torsion bar is 4340 chromoly steel, and the mount tube is 4130 chromoly steel with Delrin bushings throughout. The two-position arms are made of 2024 aluminum, and the softer position is slightly stiffer than stock (Myles used that one at Glen Helen), with the stiffer setting much stiffer than stock. The kit includes billet-aluminum HRP bar links, and Cheek went with the HRP radius-rod plate ($125).

Super-trick CMI 15-inch wheels ride on CMI hubs and provide room for the big-brake rotors. Tires are Hoosier 27.5×8.0-15 Chain-Link UTV race tires with the M500 compound and Tire Balls.


The WER Velocity 2.5 shocks are $1,799.98 a pair for the front and rear of the RS1. They greatly upgrade performance over the OEM WER RS1 needle shocks, as the lowered piggybacks improve bottoming resistance while providing a smoother, compliant ride over chop. They also incorporate a more highly tuned form of WER’s needle-valve technology to further resist bottoming. Velocities have dual-rate compression adjusters, true dual-rate shock springs with adjustable cross-over rings, 7/8-inch steel shock shafts with Viton O-rings, steel FK spherical bearing shock ends, and hard-anodized billet-aluminum 2.5-inch shock bodies. They’re completely rebuildable and are custom-valved, along with being 100-percent American-made. They’re protected by Ebbco Offroad’s carbon fiber shock guards, which are $399.95 for all four. Ebbco also makes carbon fiber CV boot/axle guards for $69.95 a pair, and they’re lighter and stronger than the OEM plastic guards.

Pro racers easily overheat the stock RS1 brakes, so Chuck Cheek fabricated the mounts, guards and rotors for the CMI big-brake conversion. Solid brake lines cut down on expansion for a more solid pedal. The bearing carriers are also CMI upgrades.


Chuck fabricated the CMI custom RS1 exhaust with a huge outlet and carbon fiber hanger. The custom intake with huge oval K&N filter is also CMI, and Benchmark Performance did the custom-tune on the RS1 ECU. The clutch itself is stock RS1, but the cover has quick-release pins and a custom screen, which is covered by a pre-filter when racing. LOORRS engine-mod rules only allow custom intake, exhaust and ECU tune, and engines are sealed. CMI axles also beef up the drive-line. The removable nerf bars and rear bumper are by B&D Performance.

Cheek also fabricated a really clean engine-oil cooler with twin fans and an engine breather and oil-recovery system. Benchmark Performance did the ECU tune for class-winning power.

Inside the cockpit, a Sparco seat rides low, and Myles also uses a Sparco steering wheel and harness. HRP sells the Sparco Evo Low QRT seat for $850 and the Evo QRT for $825. Myles uses an HRP RS1 shifter with a special Mike Skinner shift ball. Myles doesn’t use a steering quickener, but his steering wheel has a custom billet-aluminum CMI tilt-mount. He also uses an Aim MX UTV lap counter and data acquisition unit.

Lowering the Sparco seat to the floor of the RS1 meant the OEM fuel cell had to be removed, so Cheek fabricated this beautiful racing fuel cell with EFI fuel pump to ride over the front diff.

LOORRS rules state that RZRs and RS1s must weigh 1600 pounds, including the driver, and Yamahas have to weigh 1820 pounds. Talon 1000Rs must weigh 1700 pounds, and Teryx KRX1000s must weigh 1750 pounds. The stock RS1 weighs 1340 pounds dry.

See UTV Action’s full test on the Polaris RZR RS1 here:


CMI Precision Machining

527 Fee Ana St.

Placentia, CA 92870

(714) 528-3000

Ebbco Offroad

25861 Holland Rd.

Menifee, CA 92584

(951) 326-7721

Holz Racing Products

6226 Chasteen Road

Lynden, Washington 98264

(360) 398-7006

[email protected]

Walker Evans Racing

2304 Fleetwood Drive

Riverside, CA 92509

(951) 784-7223

You might also like

Comments are closed.