CORBIN LEAVERTON’S HRP RZR PRO-XP
Corbin Leaverton dominated the 2019 World Off-Road Championship Series (WORCS) Pro Stock 1000 season, winning the title by 43 points over Beau Baron and clinching four wins with two more podiums. Leaverton switched to the Pro Production Turbos for 2020 in a Holz Racing Products (HRP) RZR Pro XP Turbo, and he has racked up four wins out of six rounds and has a 23-point lead over Davi Haagsma with one round remaining at press time. Corbin Leaverton’s HRP RZR Pro-XP is full of performance and durability upgrades every Pro XP owner will want to know about.
HOLZ RACING SHORT-COURSE PRO XP BUILD
Mark Holz built Corbin Leaverton’s HRP RZR Pro-XP, starting with the $4950 72-inch HRP suspension kit. HRP developed the 4130 chromoly tubular A-arms with internal gussets and Tig welding to use OEM pivot sleeves and mounting hardware with high-strength FK precision ball joints and heat-treated steel alloy misalignment ball-joint pins. They come with bushings installed and black powdercoat standard, but other colors are available. Trailing arms are also 4130 chromoly sheet metal with internal gussets for strength and less unsprung weight, and they come with sealed spherical bearings installed.
HRP tie-rods are 7075 aircraft-grade aluminum with high-strength, three-piece FK precision rod ends, heated-treated 17-4 stainless steel rack clevis and misalignment tapered pins. HRP radius rods are 4130 chromoly tubes with billet-machined 4130 chromoly ends and sealed spherical misalignment spacers. They mate with an HRP rear chassis brace that has double-shear rod mounts and Tig-welded 4130 sheet construction. The 72-inch kit adds travel, stability and front-tire clearance to all 2020 RZR Pro XP models. The kit can be had with HRP half shafts for another $1200, trailing-arm guards for $125 and/or sway-bar links for $149.95.
Corbin runs the CNC-machined billet-aluminum HRP sway-bar links with 17-4 SS misalignment spacers and UHMW trailing-arm guards, but he uses RCV Series II axles, which are claimed to be twice as strong as the OEM axles. Series II axles have sealed outboard CVs with 4340 chromoly bodies and 300M internals and axle shafts for extreme racing conditions. The +4-inch RCVs are $775 each for fronts and $825 each for rears. Leaverton runs CMI’s Big Brake rotors with billet-aluminum mounts for Willwood calipers and CMI bearing carriers. HRP sells Walker Evans Racing’s Velocity 2.5 piggyback shocks for $3600 a set, but Corbin runs WER 2.5 needle shocks with Eibach dual-rate springs.
Holz builds the HRP Deluxe Race cage out of 1.75-inch 4130 chromoly tubes with one front anti-intrusion bar and seriously triangulated rear for mounting the twin-fan C&R radiator. The HRP low-profile Race cage is CNC-machined, mandrel-bent and powder-coated red. The cage, lowered seat, number plates, dash, firewall, radiator-relocate, billet steering column, window net and roof are $5000, and Pro XP door inserts are $129.95. Holz incorporates side braces from roof to floor for the Pro XP quarter doors and HRP inserts, and the cage is completely bolt-on. Corbin runs a large C&R intercooler and a Jazz Racing fuel cell where the passenger seat usually sits.
HRP sells the Sparco Evo QRT racing seat for $825, and the newest version has an ultra-light shell, reduced shoulder-bolster dimensions and raised harness slots for taller drivers. QRTs also have the most rake for a laid-back driver’s position. Corbin also uses a Sparco 375 suede-leather steering wheel ($250) with HRP quick-connect hub (159.95) and adapter ($49.95), and a Mastercraft five-point, 3-inch safety harness ($134.95).
ADDING SHORT-COURSE ARMOR
HRP’s Pro XP pre-runner front bumper provides bolt-on protection with Tig-welded, 1.5-inch DOM tubes and a 1/8-inch aluminum skid plate. The bumper also includes tabs for Corbin’s Rigid LED 10-inch light bar. The HRP bumper is powdercoated black with a raw skid plate, and all mounting hardware for $369.95. The pre-runner rear bumper is $359.95 with similar construction and 4130 chromoly mounting tabs. HRP’s rear skid plate is $119.95 and made of UHMW plastic extending farther back to protect the transmission and rear chassis components. HRP nerf bars are $299.95 a pair.
Leaverton runs 30×10-15 Tensor DS tires ($232.09 each) on Method 401-R beadlock rims. The 401-R is made of A356 aluminum with T6 heat-treating, a reinforced inner lip, forged 6061 V.2 bead-lock rings and Grade 8 bolts, all for $299 each. Each 401-R is rated for 1600 pounds, and the Tensor DS 30 is rated at 1200 pounds and weighs 30.9 pounds.
PRO PRODUCTION POWER AND CLUTCH
Leaverton runs Evolution Powersports’ Maptuner Power Package ($949) and charge tube ($179) with a custom Carven-R Performance exhaust muffler ($92.99) mated to the Pro XP header. With an Evo Stage 2 tune, the Pro XP puts out 204 horsepower and 167 wheel horsepower at 17-psi boost. HRP puts that power to the ground with its clutch weights ($149.95), 160/260 secondary clutch spring ($24.99), a 43-degree non-EBS billet-aluminum helix ($125), clutching spring washer kit (18.95) and CVT belt ($199.99). HRP’s clutch weights redistribute weight from the center to the tip for improved engagement, back shifts, belt grip and acceleration. The non-EBS helix reduces engine braking for jumps and corners.
Holz Racing Products
6226 Chasteen Road
Lynden, Washington 98264
CMI Precision Machining
527 Fee Ana St.
Placentia, CA 92870
Walker Evans Racing
2304 Fleetwood Drive
Riverside, CA 92509
See UTV Action’s full test on the RZR Pro XP 4 here: https://utvactionmag.com/2020-polaris-rzr-pro-xp-4-utv-action-full-test/