SR1 Class Rule Book — Version 3.1
Highlighted text is new or changed from the 2020 rules. Sections tagged NEW are new in full.
Quick Specs
| Engine | Stock Yamaha R1, 2004–2014, center mounted |
| Induction | Naturally aspirated; no turbo, supercharger or nitrous |
| Drivetrain | Stock 6-speed, direct chain drive, no differential |
| Chassis | Weller Racing SR1 base frame and engine mount kit required; you build the rest of the chassis |
| Dimensions | 83" max wheelbase, 78" max width |
| Suspension | A-arms front and rear, +6" minimum over stock 2004–2007 Yamaha Rhino, one coil-over per wheel, 10" max shaft travel |
| Tires | Any 6-ply knobby UTV tire up to 26", run as manufactured (no grooving or treatments) |
| Fuel | Pump gas (up to E10) or VP UTV96 |
| Weight | 1,600 lb minimum with driver |
| Driver | 18 and over; driver only |
Summary only. The full rule book below governs.
1. Authority and Scope NEW
1.1 Name
1.1.1The class is named SR1, written as one word — SR1, not SR-1, SR 1 or Sr1. Any other form used by a sanctioning body, entry form or results sheet refers to this class.
1.2 Purpose
1.2.1This is the official technical rule book for the SR1 class. It defines the vehicle. It does not define competition procedure.
1.2.2The SR1 class exists to provide a low-cost, technically stable short course off-road race car, and a genuine step between entry-level and professional classes.
1.3 Use and Interpretation
1.3.1This rule book is published for use by sanctioning bodies that run an SR1 class. At any event, interpretation and enforcement of these rules rest with that event’s sanctioning body and its technical officials, whose decisions are final.
1.3.2The current version is the one posted at sr1racing.com. No printed copy is official.
1.4 Relationship to Sanctioning Body Rules
1.4.1This rule book is the class technical layer and works under the general rules of any sanctioning body.
1.4.2Where this rule book is silent, the sanctioning body’s rules apply in full, including registration, licensing, conduct, flags, starts, scoring, points, penalties, protests and pit rules.
1.4.3On safety or competition procedure, the sanctioning body’s rules govern. On class technical specification, this rule book governs, except where the sanctioning body sets a stricter limit.
1.4.4SR1 is recognized by Championship Off-Road Racing (CORR) as Class 14 under Official Rule Book v6.1: SR1 vehicle; maximum 1000cc naturally aspirated; no turbochargers, superchargers or nitrous; weight, fuel and all other vehicle specifications per this rule book.
1.5 Existing Vehicles
1.5.1No vehicle built to a prior published version of this rule book will be made ineligible by a later version, except where required by a sanctioning body or for safety. On adoption of this version, Section 2.4 grandfathers Rhino- and Teryx-based vehicles built before January 1, 2020; this provision applies to vehicles built to this version and later versions.
1.6 Assumption of Risk and No Liability
1.6.1This rule book is a technical specification only. It is not a guarantee against injury, dismemberment or death, and it creates no warranty of any kind as to the safety or fitness of any vehicle, component or racing activity.
1.6.2Compliance with this rule book does not mean a vehicle is safe. Each competitor is solely responsible for the design, construction, condition and safe operation of their vehicle and safety equipment, and participates at their own risk.
1.6.3Naming a manufacturer, part or part number in this rule book is a technical specification, not an endorsement or warranty. The authors and publishers of this rule book, and the manufacturers of any parts named in it, accept no liability arising from its use.
2. Class Definition and Eligibility
2.1 Class Definition
2.1.1SR1 is a purpose-built short course off-road race car with a transplanted motorcycle power plant, built to a common specification, with the engine center mounted between the seat locations. A passenger seat may be fitted, but only one participant, the driver, may be in the vehicle during competition.
2.1.2SR1 is a spec class. Components not expressly permitted by this rule book are not permitted.
2.2 Class Intent NEW
2.2.1SR1 is a driver’s class. The car is deliberately specified with less mechanical grip than the engine can use. This is intentional.
2.2.2Competitive advantage is meant to come from driver skill and setup within a narrow window — not from power, budget or component development. This rule book shall be interpreted in favor of this intent.
2.3 Eligible Vehicles
2.3.1A vehicle built after the effective date of this version shall use a Weller Racing SR1 chassis. Vehicles built on a Yamaha Rhino or Kawasaki Teryx base center frame are eligible only as Grandfathered Vehicles under Section 2.4.
2.3.2The chassis may be reinforced for durability and strength but shall retain its stock width, length, configuration and factory suspension geometry. Stretched chassis are not permitted.
2.3.3All chassis joints shall be welded and securely attached to the frame. No bolt-on connections to the chassis are permitted.
2.4 Grandfathered Vehicles NEW
2.4.1A vehicle built on a production Yamaha Rhino base center frame, or on a production Kawasaki Teryx base center frame of model year 2019 or older, is eligible as a Grandfathered Vehicle where it was built before January 1, 2020.
2.4.2Proof. The owner shall prove the vehicle was built before January 1, 2020 with date-stamped photographs or other dated documentation, such as receipts or race results. The sanctioning body’s technical officials decide whether the proof is sufficient. A vehicle without accepted proof is not a Grandfathered Vehicle.
2.4.3Frame. A Grandfathered Vehicle shall keep the stock width, length, configuration and factory suspension geometry of its base frame. A-arm mounting points stay in their stock locations and may be reinforced with gussets and plates.
2.4.4Engine. A Grandfathered Vehicle may run the engine the 2020 Update permitted for its frame (Appendix A, Part 2): Rhino frame — Yamaha YZF-R1, 2002–2014; Teryx frame — Kawasaki ZX-10R, 2004–2010. All of Section 3 applies to that engine; where Section 3 names Yamaha, the grandfathered engine’s manufacturer is meant.
2.4.5Every other section of this rule book applies to a Grandfathered Vehicle in full, including minimum weight, tires and safety equipment.
2.4.6Grandfathered status is not available to any vehicle built on or after January 1, 2020, or to any vehicle powered by an engine not listed in Appendix A.
2.5 Driver Eligibility
2.5.1Minimum driver age is eighteen (18) years. This applies even where the sanctioning body allows younger drivers.
2.5.2Licensing, entry, waiver and release requirements are governed by the sanctioning body. A driver new to the class shall complete the sanctioning body’s rookie orientation, where one exists, before first competition.
3. Engine
3.1 Approved Engines
3.1.1The only engine permitted in a vehicle built on a Weller Racing SR1 chassis is the Yamaha YZF-R1, model years 2004 through 2014, as listed in Appendix A, Part 1. Grandfathered Vehicles may instead run an engine listed in Appendix A, Part 2.
3.1.2No other engine, of any manufacturer, displacement or model year, is permitted. Engine cases and internal components shall be from the approved model-year range; parts may be mixed across the 2004–2008 and 2009–2014 generations only where they interchange as produced.
3.1.3The engine shall be center mounted between the driver and passenger seat locations using the Weller Racing SR1 engine mounting plates. Rear-, forward- and sideways-mounted engines are not permitted.
3.1.4The tip-over sensor shall be left intact and in working order, and shall shut off the fuel pump in a rollover. Technical officials may test it by removing the sensor and rotating it.
3.2 Induction
3.2.1Turbochargers, superchargers and nitrous oxide systems are prohibited.
3.2.2The intake above the throttle bodies is open: airbox, air filter, velocity stacks, ducting and plenum are unrestricted. (2020 rules: air filter modifications only.)
3.2.3Throttle bodies shall be OEM for the engine and unmodified. Everything from the throttle body inlet flange inward — throttle bodies, injectors, intake ports and all internal components — shall remain stock. The engine shall use the factory EFI system for its model year.
3.3 Stock Engine Requirement
3.3.1Engine cases, cylinder heads and all internal components, including transmission components, shall be stock OEM for the engine’s model year. No internal modifications of any kind are permitted.
3.3.2Clutch plates and springs are the only exception: aftermarket clutch friction plates, drive plates and springs are permitted.
3.3.3Displacement shall not be increased beyond stock for the engine’s model year. The 1000cc series limit is not an allowance to exceed stock.
3.3.4Exhaust: aftermarket headers and mufflers are permitted. The exhaust shall be at least 6 inches from any fuel line.
3.3.5Cooling: oil coolers and radiators ahead of the driver or in the driver compartment shall be shrouded to prevent liquid reaching the driver if they rupture or leak. Radiators shall not be located in the cockpit. Hoses running through the driver compartment shall be shielded; braided hose is not a shield.
3.3.6Each vehicle shall start the race with a functional generator or alternator, fan, water pump and complete electrical system, and shall be self-starting by an onboard electric starter.
3.3.7Any modification not expressly permitted in this Section is prohibited.
3.4 ECU and Driver Aids
3.4.1Only the factory ECU is permitted. Aftermarket ECUs are prohibited. The factory ECU may be flashed or tuned.
3.4.2Traction control, launch control and any other driver aid that automatically intervenes in engine output are prohibited.
4. Drivetrain
4.1The stock transmission and clutch design that came with the engine shall be used. Gearbox internals stay as produced; aftermarket gear sets are prohibited.
4.2Final drive shall be direct chain drive using the Weller Racing carrier system. Differentials and FNR boxes are prohibited.
4.3Sprocket sizes and final drive ratio are free.
4.4Shifting shall be by a stick-shift style shifter, with a clutch pedal on the floor or a clutch lever on the shifter. Electric paddle shifters, automatic clutch systems and shift interrupters are prohibited.
5. Chassis and Bodywork
5.1Maximum length is 83 inches, center of front hub to center of rear hub. Maximum width is 78 inches, outside of tire to outside of tire at the widest point. All measurements are made by the sanctioning body’s officials with their instruments.
5.2The vehicle shall keep an appearance similar to a stock UTV, with a full body including bed sides. Fins, scoops, wings and other extruding additions are prohibited. Body plastics shall be fastened with no exposed areas.
5.3Fenders shall be securely attached at the start of a race. Removing fenders during competition for any reason other than race damage is a disqualification. A loop body-mounting bracket is required, and fenders shall leave no sharp extrusion when removed.
5.4The entire roof shall be covered with sheet metal or aluminum of at least .063 inch.
5.5Front and rear bumpers are required, securely attached, rounded, with no open ends or sharp edges.
5.6Nerf bars are required on both sides, closed loop with no open ends.
5.7No titanium or other exotic materials or fasteners may be used anywhere on the vehicle except the exhaust.
5.8All fuel and brake lines, including metal lines and fittings, shall be clamped and/or safety wired.
6. Suspension, Steering and Brakes
6.1A-arm suspension is required front and rear, at least 6 inches over stock. Stock suspension, suspension less than +6 inches, and trailing arms or other non-A-arm designs are not permitted.
6.2A-arm mounting points shall remain in their stock locations on the frame and may be reinforced with gussets and plates.
6.3There shall be one, and only one, shock absorber per wheel, in working condition at the start of the race. The only permitted torsion system is a coil-over shock. Maximum shock shaft travel is 10 inches, front and rear. Shock mounting points may be moved.
6.4Bump stops shall be the solid type.
6.5Steering shall be rack and pinion, in good condition and proper working order. Power steering is permitted.
6.6Brakes shall be in safe working condition and able to lock all four tires. Turning or cutting brakes are prohibited.
7. Wheels and Tires
7.1 Tires
7.1.1Any 6-ply knobby UTV tire up to 26 inches overall diameter is permitted. Hoosier-style or race-compound tires are not permitted.
7.1.2Maximum overall tire diameter is 26 inches. The tire limit is a defining feature of the class and shall not be relaxed as a technical adjustment.
7.1.3One tire per corner. Wheel spacers are permitted within the 78 inch width limit.
7.1.4Beadlocks are permitted with recessed bolts that do not protrude past the face of the ring; button-head bolts where the bolt area cannot be recessed.
7.1.5Tires will be visually inspected and must be reasonably safe.
7.2 Tire Treatment NEW
7.2.1Tires shall be run exactly as manufactured. Prohibited without exception: cutting, grooving, siping or needling; buffing, shaving or grinding; soaking or softening with any chemical; heating, tire warmers or any thermal treatment; and any substance inside the tire other than air or nitrogen.
7.2.2Officials may check tires at any time by comparing them with a known-good sample of the same tire. Officials may mark tires at inspection; only marked tires may then be used for that event. Violation is a disqualification from the event.
8. Weight
8.1Minimum vehicle weight is 1,600 pounds with the driver, in as-raced condition with the driver in full safety gear. This applies equally to Grandfathered Vehicles.
8.2Vehicles may be weighed before or after competition. Failure to present for weighing, loose ballast, or being under weight after a race is a disqualification from that race.
9. Fuel
9.1Permitted fuels are limited to (a) gasoline sold at a retail service station for highway vehicles, any octane, with no more than 10% ethanol as sold; and (b) VP Racing UTV96, as supplied. No other fuel is permitted. (2020 rules: pump gas, racing gasoline or aviation gas.)
9.2Prohibited: all other racing gasolines; aviation gasoline; methanol; ethanol blends above 10%, including E15, E85 and E90-type race fuels; nitromethane and all nitro compounds; nitrous oxide; octane boosters and additives of any kind; and blending of fuels.
9.3Officials may sample and test fuel at any time by comparing it with a known-good sample of pump gasoline or UTV96. Fuel that does not match a permitted fuel is a violation. Fuel cooling and refueling in staging are prohibited.
9.4 Fuel Cell
9.4.1A commercially made safety fuel cell is required; the stock tank shall be removed. Maximum capacity is 12 gallons. The cell shall be filled from and vented to the outside of the vehicle.
9.4.2Fillers and vents shall have rollover check valves. Filler caps shall be positive-locking and non-vented, secured so they can’t be knocked off or open; Monza and flip-type caps are prohibited. A splash shield shall direct spills away from the driver, engine and exhaust. The cell shall not vent into the driver compartment.
9.4.3The cell shall be mounted to the chassis, not the skid plate, separated from the driver by a structural cross member, and protected from ground obstacles. A cell in the passenger area shall be fully enclosed in sheet metal or aluminum.
9.4.4A firewall shall separate the driver from fuel, fluids and acids; a replacement firewall shall be at least .063 inch aluminum.
10. Electrical and Transponder
10.1An on/off switch labeled “ignition on/off” shall be on the left side of the dash, reachable from outside the vehicle, inside a red circle at least 1 inch wide. It shall shut the engine off and disconnect all electrical power. Any electric fuel pump on its own switch shall be labeled “fuel on/off” and reachable by the driver and from outside.
10.2Batteries shall be secured with metal-to-metal tie-downs or metal brackets. Wetted fiber or gel cell only; liquid lead acid is prohibited. A battery in the driver compartment needs an adequate firewall or the factory engine cover.
10.3A transponder as specified by the sanctioning body is required (CORR: MyLaps MX type), mounted 10 inches back from the leading edge of the front bumper on the passenger side unless the series says otherwise. Charging and installation are the competitor’s responsibility.
11. Safety Equipment
The requirements below follow CORR v6.1. Where the sanctioning body’s rules are stricter or have been updated, they govern.
11.1 Driver Equipment
11.1.1Full-face helmet meeting Snell SA2020, D-ring straps only.
11.1.2Fire suit: one-piece, two-layer, neck to ankle and wrist, SFI 3.2A/5. A single-layer suit requires Nomex underwear. Racing gloves and racing shoes are required.
11.1.3Five-point harness for the driver, with quick-release lap belt, two shoulder belts and a sub-belt, mounted to the cage. Bolt-in belts use Grade 8 bolts of at least ⅜ inch. Push-button, Y-type shoulder and cam-lock belts are prohibited.
11.1.4A head and neck restraint is required whenever the vehicle is on course.
11.1.5Harnesses and window nets shall not be used more than two (2) years past their date of manufacture, regardless of condition.
11.2 Roll Cage
11.2.1An aftermarket roll cage of DOM or 4130 chromoly is required; no seamed tubing. Minimum tubing is 1½ inch diameter by .095 inch wall.
11.2.2The cage shall have one front hoop, one rear hoop, two top bars placed as far outboard as possible, two rear down braces, one diagonal brace and all necessary gussets. Rear down braces and the diagonal shall be at least 30 degrees from vertical, with a cross member at the bottom of the diagonal.
11.2.3The top left half of the cage above the driver’s head shall have a 1½ x .095 inch ‘X’ brace and/or .125 inch aluminum plate (a single diagonal is enough with plate), bolted with two bolts per side. The roof shall have a cross bar for top impact.
11.2.4At least 3 inches between the helmet and any part of the cage. Cage parts the helmet could touch shall be padded.
11.2.5Gussets are required at all major intersections, including the diagonal and rear down braces. Gussets shall be at least .125 x 3 x 3 inch plate, formed corner tubing, or tubing gussets the same wall thickness as the main cage. (2020 rules: .090 inch plate.)
11.2.6Driver-compartment tubes shall be double-shear mounted. No single-shear point is permitted anywhere on the cage.
11.2.7Welds shall be high quality with full penetration and no undercut. All construction is subject to approval by the sanctioning body’s officials.
11.3 Doors and Driver Compartment
11.3.1Doors shall have ‘X’, ‘A’ or ladder bracing: X or A in 1½ x .095 inch 4130 or DOM; ladder in 1½ x .095 inch rails with 1¼ x .095 inch rungs. Doors that latch or open are not permitted. The door area shall be covered with .063 inch sheet metal or aluminum, full coverage, no half doors.
11.3.2The driver shall be able to get in and out unassisted and with ease, with the vehicle in any position. An engine cover shall cover the motor and protect the driver.
11.3.3A window net is required on the driver side, meeting SFI 27.1 with a legible label, mounted inside the cage so the driver can release it unassisted. A torn, damaged or expired net shall be replaced before competing. A passenger-side net is not required.
11.3.4At least one seat designed for racing, from a recognized racing seat maker, is required (passenger seat optional). Each seat shall be securely mounted to the frame with no sliding rails.
11.3.5A fire extinguisher is required, mounted outside the car and reachable by safety crews, with a quick release. A fire suppression system may be used instead.
11.3.6Rock screen: a securely fastened rock screen covering at least 50% of the front window opening is required. Openings no larger than 1½ x 1½ inch, with at least .125 inch of material between openings; one optional cutout up to 7 x 10 inches; no zip-tie mounting. Required at CORR events by the January 2027 Las Vegas race.
11.3.7A rear view mirror of at least 6 square inches is recommended.
12. Numbers and Identification
12.1Race numbers are assigned by the sanctioning body. The #1 plate is reserved for the current SR1 class champion.
12.2Numbers shall be on the front left of the windshield area or visor, the rear, both sides, and the roof. Minimum digit heights: front 4 inches; sides 6 inches; rear 6 inches; roof 12 inches. Recommended plate size 10 x 14 inches.
12.3Numbers shall be block style, one color and font, on a contrasting background, with no outlines, stacking or shadows; slant up to 25 degrees allowed. Side numbers mount high and toward the rear, not on doors. No foil, reflective or tape numbers. A number that can’t be read by scoring may not be scored.
13. Technical Inspection and Protests NEW
13.1All vehicles shall pass technical inspection before entering staging or the course, and shall exit the course through tech. Any vehicle may be inspected at any time during an event.
13.2Post-race inspection may include weight and any inspection the sanctioning body chooses. Refusing inspection or weighing is a disqualification.
13.3Protests follow the sanctioning body’s rules. Under CORR v6.1: filed by a competitor in the same class, on the official form, within 30 minutes of the race; $1,000 cash for engine protests plus $200 per additional item; $100 non-refundable for all other protests.
13.4Technical questions and pre-approvals go to the sanctioning body’s technical department.
Appendix A — Approved Engines
Part 1 — All vehicles
| Make | Model | Model years | Displacement | Minimum weight (with driver) |
|---|---|---|---|---|
| Yamaha | YZF-R1 | 2004–2014 | 998cc | 1,600 lbs |
Part 2 — Grandfathered Vehicles only (Section 2.4)
| Make | Model | Model years | Base frame | Minimum weight (with driver) |
|---|---|---|---|---|
| Yamaha | YZF-R1 | 2002–2014 | Yamaha Rhino | 1,600 lbs |
| Kawasaki | ZX-10R | 2004–2010 | Kawasaki Teryx (2019 or older) | 1,600 lbs |
Appendix B — Revision History
| Version | Date | Summary |
|---|---|---|
| 3.1 | October 30, 2026 | Full rewrite. New builds on the Weller SR1 chassis with R1 2004–2014; Rhino/Teryx cars built before 2020 grandfathered with their 2020 engines. Intake open above the throttle bodies. No traction or launch control. Open 26-inch knobby tire rule kept from 2020; tire-treatment ban added. Pump gas (up to E10) or VP UTV96 only. Safety and numbers harmonized with CORR v6.1. |
| 2020 Update | December 2020 | Update to R2015: minimum weights, no Hoosier-style tires, Honda engines removed. Referenced by CORR v6.1. |
| R2015 | March 2015 | Original SR1 UTV Class Rule Book. |