Why Rule Updates are Important

Rule updates are essential in 1/28 scale racing because they help maintain fair competition, adapt to evolving technology, and keep the sport accessible to both new and experienced racers. As manufacturers develop new motors, chassis designs, and electronic components, rules need to evolve to prevent any single technological advantage from dominating the field and pricing out competitors. Regular updates also address unforeseen loopholes or issues that emerge through real-world racing experience, ensuring that driver skill remains the primary factor in winning rather than simply having the newest or most expensive equipment. Additionally, rule changes can improve safety standards, clarify ambiguous regulations that lead to disputes, and keep the racing format fresh and engaging for participants and spectators alike. Without periodic rule updates, 1/28 scale racing risks becoming either a technological arms race where only those with deep pockets can compete, or a stagnant hobby that fails to incorporate beneficial innovations that could enhance the racing experience for everyone involved.

28SRA Class Rules - Grand Prix Classes

Box Stock

BOX STOCK CLASS REGULATIONS

DRIVER RESTRICTIONS

  • Lipo 3500, 2wd Mod, AWD Mod, Lipo 2500 Pan, or Open Pan drivers are not permitted in Box Stock class.

CHASSIS

  • Allowed: Kyosho MR03S, MR03S2, MR03 RTR, MR04 RWD, Associated SR27 (RWD only)
  • Not Allowed:Shaving chassis or removing sections for weight reduction
  • Chassis must be raced as manufactured from the box

WHEELBASE

  • Only allowed wheelbases: RWD 90mm, 94mm, 98mm, and 102mm

MOTOR & ESC BOARD

  • Kyosho MZ9P, MZ9E Motor from RWD RTR
  • Permitted modifications:
    • Changing motor wires with same or maximum (20) gauge wire 
    • Removing safety switch
    • Motor must be run as manufactured with no other manipulations or modifications
  • Not Permitted: EVO Board or other upgraded board

GEAR RATIO

  • 6T - 9T Pinion (included with RTR kits)
  • Stock Kyosho Gear Diff only

WHEELS

  • All brand plastic and aluminum 1/28 scale production wheels allowed
  • Size limitations:
    • Maximum front-wheel width: 8.5mm (not including outer flange/disk)
    • Maximum rear-wheel width: 11mm (not including outer flange/disk)
    • Maximum wheel diameter: 20mm
    • Minimum wheel diameter: 19mm
  • Wheels must be original designs made for 1/28 scale cars
  • Wheel and tire must fit inside the body

TIRES

  • Maximum tire diameter (mounted): 25.5mm
  • Front tires must be 8.5mm and rear tires 11mm
  • Not Allowed:
    • Traction compound on tire or race surface
    • Tire warmers
    • Homemade tires
    • Foam tires
    • Silicon tires
    • Urethane tires
    • Ethyl Carbonate tires
    • Tire inserts
  • Tires may be cleaned with 70% alcohol solution or water
  • Using illegal tire cleaner will result in penalties
  • Direct tire-related questions to the driver's meeting or race director

BATTERIES

  • Cars must be powered by 4 AAA batteries
  • Allowed types: Alkaline, Ni-MH, or Ni-Cd
  • An additional battery is allowed only for transponder connection

ELECTRONICS & TRANSMITTER

  • Stock Radio from RTR Kit
  • Only Kyosho original items included in the RTR box are allowed
  • No modifications to radio permitted

BODY

  • Any manufactured molded hard shell that fits the allowed wheelbase
  • All parts must be original for that body
  • Limited wheel and ground clearance modifications allowed
  • Size limitations:
  • Maximum body length: 180mm
  • Maximum width: 83mm
  • Not Allowed:
    • Shaving/thinning body material for weight reduction
    • Lexan roofs, windows, and wings
  • Headlight requirements:
    • Original headlight covers must be installed
    • Headlight buckets may be removed/omitted
    • Lost headlight covers may be replaced with decal/tape
  • Taillights and covers may be removed/omitted
  • Small body parts (mirrors, canards, exhausts, front splitters) may be omitted to prevent racing damage
  • Wings: Standard rear wings for corresponding hard-shell body may be used with no height limit
  • Custom aftermarket plastic wings must meet 45mm height limit from ground

OPTION PARTS

  • Allowed from any manufacturer: bearings, wheel nuts, springs, and T-Plates
  • Only original Kyosho front and rear suspension parts may be used
  • No added weight via tungsten, brass, or other materials

MODIFICATIONS

  • King pin flip allowed, lower pin must be shortened to no damage track

AAA 3500

AAA 3500 CLASS REGULATIONS

CHASSIS

  • Allowed models: Kyosho MR03S, MR03S2, & MR03 RWD, MR04 RWD, Jomurema, MRC MRC01, PN PNR2.5W

WHEELBASE

  • Only allowed wheelbases: 90mm, 94mm, 98mm, and 102mm

MOTOR

  • Any manufacturer 3500Kv motor ( must run sensorless- no sensor wires attached)
  • Maximum can diameter: 15mm
  • Maximum Kv: 3800
  • No aftermarket rotors allowed
  • Motors must not be tampered with or modified

GEAR RATIO

  • Any manufacturer pinion and spur allowed
  • Tooth count must be distinguishable by markings or color for easy tech
  • All gears must be Pre-Event teched and painted
  • Standard ratio: 53T Spur, 16T pinion (unless specified for track conditions by event)

WHEELS

  • All brand plastic and aluminum 1/28 scale production wheels allowed
  • Size limitations:
    • Maximum front-wheel width: 8.5mm (not including outer flange/disk)
    • Maximum rear-wheel width: 11mm (not including outer flange/disk)
    • Maximum wheel diameter: 20mm
    • Minimum wheel diameter: 19mm
  • Wheels must be original designs made for 1/28 scale cars
  • Wheel and tire must fit inside the body

TIRES

  • Maximum tire diameter (mounted): 25.5mm
  • Front tires must be 8.5mm and rear tires 11mm
  • Tire warmers are allowed
  • Tires may be cleaned with 70% alcohol solution or water
  • Not Allowed: 
    • Traction compound on tire or race surface
    • Homemade tires
    • Foam tires
    • Silicon tires
    • Urethane tires
    • Ethyl Carbamate tires
    • Tire inserts
  • Using illegal tire cleaner will result in penalties

BATTERIES

  • Cars must be powered by 4 AAA batteries
  • Allowed types: Alkaline, Ni-MH, or Ni-Cd
  • An additional battery is allowed only for transponder connection

ESC / RECEIVER

  • Any 1/28th scale MiniZ ESC and Receiver in the same flat board configuration as the Kyosho EVO board
  • Not Allowed:
    • Receivers with built-in Gyro
    • Separate Gyros

BODY

  • Any manufactured molded hard shell that fits the allowed wheelbase
  • All parts must be original for that body
  • Limited wheel and ground clearance modifications allowed
  • Lexan roofs, windows, and wings are allowed
  • Size limitations:
    • Maximum body length: 180mm
    • Maximum width: 83mm
    • Minimum Weight: 24 grams
  • Headlight requirements: Original headlight covers must be installed
  • Headlight buckets may be removed/omitted
  • Lost headlight covers may be replaced with decal/tape
  • Taillights and covers may be removed/omitted
  • Small body parts (mirrors, canards, exhausts, front splitters) may be omitted to prevent racing damage
  • Wings: Standard rear wings for corresponding hard-shell body may be used with no height limit
  • Custom aftermarket plastic wings must meet 45mm height limit from ground

WEIGHT

  • Full car minimum weight: 160 grams (race ready)

OPTIONAL PARTS

  • Any aftermarket 1/28 scale publicly available production or 3D printed parts allowed
  • Adding weight via tungsten putty, stick weight, or cut hobby brass is allowed
  • Not Allowed: Prototype parts
  • Public availability requirements: Parts must be publicly announced via social media or website 45 days prior to race
  • Parts must be available for purchase nationally 45 days prior to race
  • 3D print files must be shared with the public 30 days before event start

Any questions concerning class rules should be addressed at the driver's meeting or with the race director.

 

Lipo 2500

LIPO 2500 CLASS 

  • Allowed models: Kyosho MR03S, MR03S2, & MR03 RWD, Jomurema, GL Racing GLR, GLR-GT, GL-GTR, MRC MRC01, PN PNR2.5W, PNR3.0, RTRC RTA, Atomic MRZ, MRX, MRV, RX28/SE G1, G2 and G3, NEXX Skyline, Specter, MWX R.1, G-Force Lightning, XBility XB 1, AE RC28

WHEELBASE

  • Only allowed wheelbases: 98mm and 102mm

MOTOR

  • Any 1/28th scale manufacturer 2500Kv sensored motor
  • Maximum can diameter: 15mm
  • Maximum Kv: 2800
  • No aftermarket rotors allowed
  • Motors must not be tampered with or modified

GEAR RATIO

  • Any manufacturer pinion and spur allowed
  • Tooth count must be distinguishable by markings or color for easy tech
  • All gears must be Pre-Event teched and painted
  • Standard ratio: 12T Pinion / 53T Spur (unless specified for track conditions by event)

WHEELS

  • All brand plastic and aluminum 1/28 scale production wheels allowed
  • Size limitations:
    • Maximum front-wheel width: 8.5mm (not including outer flange/disk)
    • Maximum rear-wheel width: 11mm (not including outer flange/disk)
    • Maximum wheel diameter: 20mm
    • Minimum wheel diameter: 19mm
  • Wheels must be original designs made for 1/28 scale cars
  • Wheel and tire must fit inside the body

TIRES

  • Maximum tire diameter (mounted): 25.5mm
  • Front tires must be 8.5mm and rear tires 11mm wide
  • Tire warmers are allowed
  • Tires may be cleaned with 70% alcohol solution or water
  • Not Allowed:
    • Traction compound on tire or race surface
    • Homemade tires
    • Foam tires
    • Silicon tires
    • Urethane tires
    • Ethyl Carbamate tires
    • Tire inserts
  • Using illegal tire cleaner will result in penalties

BATTERIES

  • 2-cell LiPo or 2 one-cells paralleled (maximum 8.40 volts)
  • Max battery dimensions 45 x 24.0 x 13.0mm
  • Battery must be identifiable with original sticker from 1/28th MiniZ manufacturer
  • Maximum 500 mAh
  • An additional battery is allowed only for transponder connection

ESC / RECEIVER

  • Any manufacturer 1/28 ESC and Receiver allowed
  • ESC must not have any timing, turbo or boost activated and have a visual Blinking LED. (Blinky Mode) LED. (Blinky Mode) 
  • Not Allowed:
    • Receivers with built-in Gyro
    • Separate Gyros

BODY

  • Any manufactured molded hard shell that fits the allowed wheelbase
  • All parts must be original for that body
  • Limited wheel and ground clearance modifications allowed
  • Lexan roofs, windows, and wings are allowed
  • Size limitations:
    • Maximum body length: 180mm
    • Maximum width: 83mm
    • Minimum Weight: 24 grams
  • Headlight requirements: Original headlight covers must be installed
  • Headlight buckets may be removed/omitted
  • Lost headlight covers may be replaced with decal/tape
  • Taillights and covers may be removed/omitted
  • Small body parts (mirrors, canards, exhausts, front splitters) may be omitted to prevent racing damage
  • Wings: Standard rear wings for corresponding hard-shell body may be used with no height limit
  • Custom aftermarket plastic wings must meet 45mm height limit from ground

OPTIONAL PARTS

  • Any aftermarket 1/28 scale publicly available production or 3D printed parts allowed
  • Adding weight via tungsten putty, stick weight, or cut hobby brass is allowed
  • Not Allowed:
    • Prototype parts
  • Public availability requirements:
  • Parts must be publicly announced via social media or website
  • Parts must be available for purchase nationally 45 days prior to race
  • 3D print files must be shared with the public 30 days before event start

WEIGHT

  • Full car minimum weight: 160 grams (race ready)

Any questions concerning class rules should be addressed at the driver's meeting or with the race director.


Formula 1

FORMULA 1 CLASS REGULATIONS

CHASSIS

  • Allowed models: GL Racing GLF-1, G-Force Formula, PNR 3.0F1, MWX R1F1, Atomic SF-F1 conversion, Reflex FX28, Xbility XB-F1

WHEELBASE

  • Only allowed wheelbase: 112mm – 116mm

MOTOR

  • Any 1/28th scale manufacturer 2500Kv sensored motor
  • Maximum can diameter: 15mm
  • Maximum Kv: 2800
  • No aftermarket rotors allowed
  • Motors must not be tampered with or modified

GEAR RATIO

  • Any manufacturer pinion and spur allowed
  • Tooth count must be distinguishable by markings or color for easy tech
  • All gears must be Pre-Event teched and painted
  • Standard ratio: 12T Pinion / 53T Spur (unless specified for track conditions by event)

WHEELS

  • All brand plastic and aluminum 1/28 scale production wheels allowed
  • Size specifications:
  • Front-wheel width: 11mm
  • Rear-wheel width: 14mm (not including outer flange/disk)
  • Maximum wheel diameter: 20mm
  • Minimum wheel diameter: 19mm
  • Wheels must be original designs made for 1/28 scale cars

TIRES

  • Maximum tire diameter (mounted): 25.5mm
  • Front tires must be 11mm and rear tires 14mm wide
  • Tire warmers are allowed
  • Tires may be cleaned with 70% alcohol solution or water
  • Not Allowed:
    • Traction compound on tire or race surface
    • Homemade tires
    • Foam tires
    • Silicon tires
    • Urethane tires
    • Ethyl Carbamate tires
  • Tire inserts
  • Using illegal tire cleaner will result in penalties

BATTERIES

  • 2-cell LiPo or 2 one-cells paralleled (maximum 8.4 volts)
  • Max battery dimensions 45 x 24.0 x 13.0mm
  • Battery must be identifiable with original sticker from 1/28th MiniZ manufacturer
  • Maximum 500 mAh
  • An additional battery is allowed only for transponder connection

ESC / RECEIVER

  • Any manufacturer ESC and Receiver allowed
  • ESC must have and be in BLINKY MODE
  • Not Allowed:
    • Receivers with built-in Gyro
    • Separate Gyros

BODY

  • Lexan F1 Bodies only: GLF-1, PN-F1, MWX, G-Force, Reflex FX28
  • Aftermarket front and rear wings allowed (must look like an F1 wing)
  • Bearings in the front wing are not allowed

OPTION PARTS

  • Any aftermarket 1/28 scale publicly available production or 3D printed parts allowed
  • Adding weight via tungsten putty, stick weight, or cut hobby brass is allowed
  • Not Allowed:
    • Prototype parts
  • Public availability requirements:
  • Parts must be publicly announced via social media or website
  • Parts must be available for purchase nationally 45 days prior to race
  • 3D print files must be shared with the public 30 days before event start

WEIGHT

  • Minimum weight: 140 grams

Any questions concerning class rules should be addressed at the driver's meeting or with the race director.

Lipo 3500 Lexan

LIPO 3500 LEXAN CLASS REGULATIONS

CHASSIS

  • Allowed models: Kyosho MR03S, MR03S2, and MR03 RWD, Jomurema, GL Racing GLR, GLR-GT, GL-GTR, MRC MRC01, PN PNR2.5W, PNR3.0, RTRC RTA, Atomic MRZ, MRX, MRV, RX28/SE G1, G2 and G3, NEXX Skyline, Specter, MWX R.1, G-Force Lightning, XBility XB 1, AE RC28

WHEELBASE

  • Only allowed wheelbases: 98mm and 102mm

MOTOR

  • Any 1/28th scale manufacturer 3500Kv sensored motor
  • Maximum can diameter: 15mm
  • Maximum Kv: 3800
  • No aftermarket rotors allowed
  • Motors must not be tampered with or modified in any way

GEAR RATIO

  • Any manufacturer pinion and spur allowed
  • Tooth count must be distinguishable by markings or color for easy tech
  • All gears must be Pre-Event teched and painted
  • Standard ratio: 12T Pinion / 53T Spur (unless specified for track conditions by event)

WHEELS

  • All brand plastic and aluminum 1/28 scale production wheels allowed
  • Size specifications:
    • Front-wheel width: 8.5mm (not including outer flange/disk)
    • Rear-wheel width: 11mm (not including outer flange/disk)
    • Maximum wheel diameter: 20mm
    • Minimum wheel diameter: 19mm
  • Wheels must be original designs made for 1/28 scale cars
  • Wheel and tire must fit inside the body

TIRES

  • Maximum tire diameter (mounted): 25.5mm
  • Front tires must be 8.5mm and rear tires 11mm wide
  • Tire warmers are allowed
  • Tires may be cleaned with 70% alcohol solution or water
  • Not Allowed:
    • Traction compound on tire or race surface
    • Homemade tires
    • Foam tires
    • Silicon tires
    • Urethane tires
    • Ethyl Carbamate tires
    • Tire inserts
  • Using illegal tire cleaner will result in penalties

BATTERIES

  • 2-cell LiPo or 2 one-cells paralleled (maximum 8.40 volts)
  • Max battery dimensions 45 x 24.0 x 13.0mm
  • Battery must be identifiable with original sticker from 1/28th MiniZ manufacturer
  • Maximum 500 mAh
  • An additional battery is allowed only for transponder connection

ESC / RECEIVER

  • Any manufacturer 1/28 ESC and Receiver allowed
  • ESC must not have any timing, turbo or boost activated and have a visual Blinking LED. (Blinky Mode)  
  • Not Allowed:
    • Receivers with built-in Gyro
    • Separate Gyros

APPROVED LIPO 3500 BODIES

  • PN: Supra A90, JSK, AD4, GT4LB, 992GT3, M4GT3, Concept C9, V2 JGT01, ZLB
  • SBRC: Zenvo ST1, Phenom GT, NSX GT3, 458GT, SBX, STR, HYR, JX, XB2
  • Marka: RK410, RK408, RK-S, RK-SP6, RK-HC, RK-P-One, RK-W, RK-12, RK-TWR, RK-4C, RK-AMGT, RK-BLD, RK-NTI, RK-PZR, RK-MK4, MK5
  • Atomic: M4Z, DBX, Hyper, VST, ADR, IS2, LTC Type, LCT-2.0, AMZ
  • GL Racing: P1M
  • Rad Body: Mako GT, Mako X, Catfish
  • PROTOform: P63, Venturi GT
  • G-Force: VW
  • RTRC: XVR-GTB
  • Bitty Designs: Ares-1, Eptron
  • Nexx Racing: NX-326 Body
  • 102mm Wheelbase Specific:
    • GL Racing – P1M
    • Marka – RK-P-One
    • RTRC – XVR-GTB
  • Wings:  Wings have 45mm height limit from ground

WEIGHT

  • Full car minimum weight: 160 grams (race ready)

OPTION PARTS

  • Any aftermarket 1/28 scale publicly available production or 3D printed parts allowed
  • Adding weight via tungsten putty, stick weight, or cut hobby brass is allowed
  • Not Allowed: Prototype parts
  • Public availability requirements: Parts must be publicly announced via social media or website 45 days prior to race
  • Parts must be available for purchase nationally 45 days prior to race
  • 3D print files must be shared with the public 30 days before event start

Lipo 2500 Pan

This class debuted in 2025 is the newest addition to the 28SRA Grand Prix.

LIPO 2500 PAN CLASS REGULATIONS

CHASSIS

  • Open any 2WD chassis ONLY
  • Prototype or pre-production chassis allowed

WHEELBASE

  • Only allowed wheelbases: 94mm, 98mm and 102mm

MOTOR

  • Any manufacturer 2500 motor allowed (sensored or sensorless)
  • 2800kv limit
  • Maximum can diameter: 15mm

GEAR RATIO

  • Open 

WHEELS

  • All brand plastic and aluminum 1/28 scale production wheels allowed
  • Size specifications:
    • Maximum front-wheel width: 11mm (not including outer flange/disk)
    • Maximum rear-wheel width: 14mm (not including outer flange/disk)
    • Maximum wheel diameter: 20.5mm
    • Minimum wheel diameter: 19mm
  • Wheels must be original designs made for 1/28 scale cars
  • Wheel and tire must fit inside the body

TIRES

  • Front tires maximum width: 11mm
  • Rear tires maximum width: 14mm
  • Tire warmers are allowed
  • Tires may be cleaned with 70% alcohol solution or water
  • Not Allowed:
    • Traction compound on tire or race surface
    • Homemade tires
    • Foam tires
    • Silicon tires
    • Urethane tires
    • Ethyl Carbamate tires
    • Tire inserts
  • Using illegal tire cleaner will result in penalties

BATTERIES

  • 2-cell LiPo or 2 one-cells paralleled (maximum 8.40 volts)
  • An additional battery is allowed only for transponder connection

ESC / RECEIVER

  • Any manufacturer ESC (sensored or sensorless) and Receiver allowed.
  • Not Allowed:
    • Receivers with built-in Gyro
    • Separate Gyros

APPROVED LEXAN & LMP CAR BODIES

  • Cutting the rear panel is allowed
  • PN: BMR, AMR2
  • Marka: RK-AMR, RK-P99, RK-LM6, MRK-8031-07, MRK-8045, MRK-8046, MRK-8047
  • Reflex LMP3
  • Atomic: MP1
  • SBRC: B001, B011
  • Rad Body: LMP3 RAD001, Ocho, Skillet
  • GL Racing – VDS
  • GK Body GK-0001

OPTION PARTS

  • Open any parts allowed (including homemade parts, 3D-printed, and prototype parts)

 

AWD Mod

AWD MOD CLASS REGULATIONS

CHASSIS

  • Allowed models: Kyosho Mini-Z Racer AWD MA010, MA015, MA020 and MA030, Atomic BZ and SZ2, GL Racing GLA, GLA Giulia, Mini-Q Q7, RTRC RTB

WHEELBASE

  • Only allowed wheelbases: 98mm and 102mm

MOTOR

  • Any manufacturer motor allowed (sensored or sensorless)
  • Maximum can diameter: 16mm

GEAR RATIO

  • Open

WHEELS

  • All brand plastic and aluminum 1/28 scale production wheels allowed
  • Size specifications:
    • Maximum front-wheel width: 11mm
    • Maximum rear-wheel width: 14mm (not including outer flange/disk)
    • Maximum wheel diameter: 20.5mm
    • Minimum wheel diameter: 19mm
  • Wheels must be original designs made for 1/28 scale cars
  • Wheel and tire must fit inside the body

TIRES

  • Maximum tire diameter (mounted): 25.5mm
  • Front tires max 11mm and rear tires max 14mm wide
  • Tire warmers are allowed
  • Tires may be cleaned with 70% alcohol solution or water
  • Not Allowed:
    • Traction compound on tire or race surface
    • Homemade tires
    • Foam tires
    • Silicon tires
    • Urethane tires
    • Ethyl Carbamate tires
    • Tire inserts
  • Using illegal tire cleaner will result in penalties

BATTERIES

  • 2-cell LiPo or 2 one-cells paralleled (maximum 8.40 volts)
  • An additional battery is allowed only for transponder connection
  • ESC / RECEIVER
  • Any manufacturer ESC (sensored or sensorless) and Receiver allowed
  • Not Allowed:
    • Receivers with built-in Gyro
    • Separate Gyros

APPROVED AWD BODIES

  • PN: Supra A90, JSK, AD4, GT4LB, 992GT3, M4GT3, Concept C9, V2 JGT01, ZLB
  • SBRC: Zenvo ST1, Phenom GT, NSX GT3, 458GT, SBX, STR, HYR, JX, XB2
  • Marka: RK410, RK408, RK-S, RK-SP6, RK-HC, RK-P-One, RK-W, RK-12, RK-TWR, RK-4C, RK-AMGT, RK-BLD, RK-NTI, RK-PZR, RK-MK4, MK5
  • Atomic: M4Z, DBX, Hyper, VST, ADR, IS2, LTC Type, LCT-2.0, AMZ
  • GL Racing: P1M
  • Rad Body: Mako GT, Mako X, Catfish
  • PROTOform: P63, Venturi GT
  • G-Force: VW
  • RTRC: XVR-GTB
  • Bitty Designs: Ares-1, Eptron
  • Nexx Racing: NX-326 Body
  • 102mm Wheelbase Specific:
  • GL Racing – P1M
  • Marka – RK-P-One
  • RTRC – XVR-GTB
  • Wings:  Wings have 50mm height limit from ground

OPTION PARTS

  • Any aftermarket 1/28 scale publicly available production or 3D printed parts allowed
  • Adding weight via tungsten putty, stick weight, or cut hobby brass is allowed
  • Not Allowed:
    • Prototype parts
  • Public availability requirements:
  • Parts must be publicly announced via social media or website
  • Parts must be available for purchase nationally 45 days prior to race
  • 3D print files must be shared with the public 30 days before event start

Pan Open

PAN OPEN CLASS REGULATIONS

CHASSIS

  • Open -  any 1/28th scale 2WD chassis 
    • Production Chassis allowed
    • Prototype or pre-production chassis allowed

WHEELBASE

  • Only allowed wheelbases: 94mm, 98mm and 102mm

MOTOR

  • Any manufacturer motor allowed (sensored or sensorless)
  • Maximum can diameter: 16mm

GEAR RATIO

  • Open

WHEELS

  • All brand plastic and aluminum 1/28 scale production wheels allowed
  • Size specifications:
    • Maximum front-wheel width: 11mm
    • Maximum rear-wheel width: 14mm (not including outer flange/disk)
    • Maximum wheel diameter: 20.5mm
    • Minimum wheel diameter: 19mm
  • Wheels must be original designs made for 1/28 scale cars
  • Wheel and tire must fit inside the body

TIRES

  • Front tires maximum width: 11mm
  • Rear tires maximum width: 14mm
  • Tire warmers are allowed
  • Tires may be cleaned with 70% alcohol solution or water
  • Not Allowed:
    • Traction compound on tire or race surface
    • Homemade tires
    • Foam tires
    • Silicon tires
    • Urethane tires
    • Ethyl Carbamate tires
    • Tire inserts
  • Using illegal tire cleaner will result in penalties

BATTERIES

  • 2-cell LiPo or 2 one-cells paralleled (maximum 8.40 volts)
  • An additional battery is allowed only for transponder connection

ESC / RECEIVER

  • Any manufacturer ESC (sensored or sensorless) and Receiver allowed
  • Not Allowed:
    • Receivers with built-in Gyro
    • Separate Gyros

APPROVED LEXAN PAN CAR BODIES

  • Cutting the rear panel is allowed
  • PN: BMR, AMR2
  • Marka: RK-AMR, RK-P99, RK-LM6, MRK-8031-07
  • Atomic: MP1
  • SBRC: B001, B011
  • Rad Body: LMP3, Ocho, Skillet
  • 102mm Wheelbase Specific:
  • Atomic – MRZ
  • GL Racing – VDS
  • GK Body GK-0001

OPTION PARTS

  • Open any parts allowed (including homemade parts, 3D-printed, and prototype parts)

 

Other 28SRA Classes

Super AAA

28SRA Super AAA Class Rules

CHASSIS

Allowed Models: Kyosho MR03S, MR03S2, MR03 RWD, MR04 RWD, Jomurema, MRC MRC01, PN PNR2.5W

WHEELBASE

Allowed wheelbases: 90mm, 94mm, 98mm, and 102mm only.

MOTOR

Allowed motors (choose one):

  • Kyosho X-Speed Motor-V (black end bell, ball bearing)
  • PN Racing 70 Turn (bushing or bearing)
  • PN Racing 50 Turn (bushing or bearing)

Motor Rules:

  • White stock motors are not permitted.
  • Motor cans may not be opened. Modified armatures or rotors are not permitted.
  • Brushes and wires may be replaced only on motors that allow servicing without removing the end bell. Any motor showing evidence of end bell removal will result in disqualification.
  • Thermal cutoff devices and capacitors may be removed.

GEAR RATIO

Open gearing. No restrictions on pinion or spur material.

WHEELS

All brand plastic and aluminum 1/28 scale production wheels are allowed, subject to the following:

  • Maximum front wheel width: 8.5mm (excluding outer flange/disk)
  • Maximum rear wheel width: 14mm (excluding outer flange/disk)
  • Maximum wheel diameter: 20mm
  • Minimum wheel diameter: 19mm
  • Wheels must be original production designs made for 1/28 scale Mini-Z use.
  • Wheel and tire must fit within the body silhouette.

TIRES

Allowed:

  • Rubber 1/28th scale or Mini-Z production tires only
  • Front tires: 8.5mm maximum width (±0.5mm tolerance)
  • Rear tires: 14mm maximum width (±0.5mm tolerance)
  • Maximum mounted tire diameter: 25.5mm
  • Tire warmers are permitted
  • Tires may be cleaned with 70% isopropyl alcohol or water only

Not Allowed:

  • Traction compound on tires or race surface
  • Homemade tires
  • Foam tires
  • Silicone tires
  • Urethane tires
  • Ethyl carbamate tires
  • Tire inserts
  • Any tire cleaning agent not listed above

Penalty: Use of prohibited tire treatment or cleaning agents will result in disqualification from the affected session.

BATTERIES

  • Cars must be powered by 4 AAA batteries (alkaline, Ni-MH, or Ni-Cd).
  • One additional AAA battery is permitted for transponder use only.

ESC / RECEIVER

  • Any 1/28 scale Mini-Z compatible ESC and receiver combined on a single flat circuit board is allowed. The board must match the general flat, integrated form factor of the Kyosho EVO board.
  • Built-in gyros and separate external gyros are not permitted.

BODY

General:

  • Any commercially manufactured hard shell body that fits the allowed wheelbase is permitted.
  • All body parts must be original for that body model.
  • 102mm bodies may only be used on 102mm wheelbase chassis. Body post extenders to fit a 102mm body to a shorter chassis are not permitted.

Size Limits:

  • Maximum body length: 180mm
  • Maximum body width: 83mm
  • Minimum body weight: 24 grams (body only, without electronics or hardware)

Modifications:

  • Limited wheel arch and ground clearance modifications are allowed.
  • Lexan roofs, windows, and wings are permitted.
  • Original headlight covers must be installed. Lost or damaged covers may be replaced with decal or tape of equivalent size and shape. Headlight buckets may be removed.
  • Taillights and taillight covers may be removed.
  • Small body details (mirrors, canards, exhausts, front splitters) may be omitted to prevent racing damage.

Wings:

  • The stock rear wing corresponding to the hard shell body may be used. The wing must not exceed 80mm in width or cause the total car height to exceed 45mm from the ground.
  • Custom aftermarket plastic wings are permitted provided they do not exceed 45mm in total height from the ground and do not exceed 80mm in width.

WEIGHT

No minimum or maximum car weight. Weight may be added per the Optional Parts section below.

OPTIONAL PARTS

  • Any aftermarket 1/28 scale publicly available production or 3D printed part is allowed.
  • Weight may be added using tungsten putty, stick-on wheel weights, or cut hobby brass only.
  • Prototype or pre-production parts are not permitted.

Availability Requirements: All aftermarket parts and 3D printed parts must meet the following before use at any event:

  1. The part must be publicly announced via the 28SRA website, official social media page, or other publicly accessible channel at least 45 days before the event.
  2. The part must be available for national purchase at least 45 days before the event.
  3. If the part is 3D printed, the print file must be publicly shared and downloadable at least 30 days before the event start date.

Parts meeting requirements (1) and (2) but not yet satisfying (3) may not be used until the file sharing requirement is also met.

Any questions regarding class rules should be raised at the driver's meeting or directed to the race director prior to the start of competition.

2wd Mod

2WD MOD CLASS REGULATIONS

CHASSIS

  • Allowed models: Kyosho MR03S, MR03S2, and MR03 RWD, Jomurema, GL Racing GLR, GLR-GT, GL-GTR, MRC MR01, PN PNR2.5W, PNR3.0, RTRC RTA, Atomic MRZ, MRX, MRV, RX28/SE G1, G2 and G3, NEXX Skyline, Specter, MWX R.1, G-Force Lightning, Xbility XB1, AE RC 28
  • WHEELBASE
  • Only allowed wheelbases: 94mm, 98mm and 102mm

MOTOR

  • Any manufacturer motor allowed (sensored or sensorless)
  • Maximum can diameter: 16mm

GEAR RATIO

  • Open

WHEELS

  • All brand plastic and aluminum 1/28 scale production wheels allowed
  • Size specifications:
    • Maximum front-wheel width: 11mm
    • Maximum rear-wheel width: 14mm (not including outer flange/disk)
    • Maximum wheel diameter: 20.5mm
    • Minimum wheel diameter: 19mm
  • Wheels must be original designs made for 1/28 scale cars
  • Wheel and tire must fit inside the body

TIRES

  • Front tires maximum width: 11mm
  • Rear tires maximum width: 14mm
  • Tire warmers are allowed
  • Tires may be cleaned with 70% alcohol solution or water
  • Not Allowed:
    • Traction compound on tire or race surface
    • Homemade tires
    • Foam tires
    • Silicon tires
    • Urethane tires
    • Ethyl Carbamate tires
    • Tire inserts
  • Using illegal tire cleaner will result in penalties

BATTERIES

  • 2-cell LiPo or 2 one-cells paralleled (maximum 8.40 volts)
  • An additional battery is allowed only for transponder connection

ESC / RECEIVER

  • Any manufacturer ESC (sensored or sensorless) and Receiver allowed
  • Not Allowed:
    • Receivers with built-in Gyro
    • Separate Gyros

APPROVED 2WD MOD BODIES

  • PN: Supra A90, JSK, AD4, GT4LB, 992GT3, M4GT3, Concept C9, V2 JGT01, ZLB
  • SBRC: Zenvo ST1, Phenom GT, NSX GT3, 458GT, SBX, STR, HYR, JX, XB2
  • Marka: RK410, RK408, RK-S, RK-SP6, RK-HC, RK-P-One, RK-W, RK-12, RK-TWR, RK-4C, RK-AMGT, RK-BLD, RK-NTI, RK-PZR, RK-MK4, MK5
  • Atomic: M4Z, DBX, Hyper, VST, ADR, IS2, LTC Type, LCT-2.0, AMZ
  • GL Racing: P1M
  • Rad Body: Mako GT, Mako X, Catfish
  • PROTOform: P63, Venturi GT
  • G-Force: VW
  • RTRC: XVR-GTB
  • Bitty Designs: Ares-1, Eptron
  • Nexx Racing: NX-326 Body
  • 102mm Wheelbase Specific:
  • GL Racing – P1M
  • Marka – RK-P-One
  • RTRC – XVR-GTB
  • Wings:  Wings have 50mm height limit from ground

OPTION PARTS

  • For all approved chassis, any factory or aftermarket 1/28 scale production or 3D printed parts allowed
    • 3D print files must be shared with the public 45 days before event start
    • Parts must be available for purchase nationally 45 days prior to race
  • Adding weight via tungsten putty, stick weight, or cut hobby brass is allowed
  • Not Allowed: Prototype parts
  • Public availability requirements: Parts must be publicly announced via social media or website 45 days prior to race

AAA Spec


AAA Spec Rules
(Formerly RM Spec )

 

We have updated the RM28 Spec with a few new details and opened up some performance options. Please read! 

CHASSIS

  • Kyosho MR01, MR02, MR03, MR04, SR27 or PN 2.5 chassis

WHEELBASE

  • Only allowed wheelbases: 90mm, 94mm, 98mm, and 102mm

MOTOR

  • Kyosho MZ9P, MZ9E Motor from RTR, PN  132370
  • Permitted modifications:
    • Changing motor wires with same or maximum (20) gauge wire 
    • Removing safety switch
  • Motor must be run as manufactured with no other manipulations or modifications

GEAR RATIO

  • Open Spur, Open Pinion, Open Diff

WHEELS

  • All brand plastic and aluminum 1/28 scale production wheels allowed
  • Size limitations:
    • Maximum front-wheel width: 8.5mm
    • Maximum rear-wheel width: 11mm (not including outer flange/disk)
    • Maximum wheel diameter: 20mm
    • Minimum wheel diameter: 19mm
  • Wheels must be original designs made for 1/28 scale cars
  • Wheel and tire must fit inside the body

TIRES

  • Maximum tire diameter (mounted): 25.5mm
  • Front tires must be 8.5mm and rear tires 11mm
  • Not Allowed:
    • Traction compound on tire or race surface
    • Tire warmers
    • Homemade tires
    • Foam tires
    • Silicon tires
    • Urethane tires
    • Ethyl Carbamate tires
    • Tire inserts
  • Tires may be cleaned with 70% alcohol solution or water
  • Using illegal tire cleaner will result in penalties
  • Direct tire-related questions to the driver's meeting or race director

BATTERIES

  • Cars must be powered by 4 AAA batteries
  • Allowed types: Alkaline, Ni-MH, or Ni-Cd
  • An additional battery is allowed only for transponder connection

ELECTRONICS & TRANSMITTER

  • Any manufacturer remote is allowed
  • Only Kyosho Non-EVO ESC and Receiver in the same flat board configuration, blue or white antenna board may be used
  • Not Allowed:
    • Receivers with built-in Gyro
    • Separate Gyros

BODY

  • Any manufactured molded hard shell that fits the allowed wheelbase
  • All parts must be original for that body
  • Limited wheel and ground clearance modifications allowed
  • Size limitations:
  • Maximum body length: 180mm
  • Maximum width: 83mm
  • Not Allowed:
    • Shaving/thinning body material for weight reduction
    • Lexan roofs, windows, and wings
  • Headlight requirements:
    • Original headlight covers must be installed
    • Headlight buckets may be removed/omitted
    • Lost headlight covers may be replaced with decal/tape
  • Taillights and covers may be removed/omitted
  • Small body parts (mirrors, canards, exhausts, front splitters) may be omitted to prevent racing damage
  • Wings: Standard rear wings for corresponding hard-shell body may be used with no height limit
  • Custom aftermarket plastic wings must meet 45mm height limit from ground

OPTION PARTS

  • Allowed from any manufacturer: All upgrades are open except Motor, Body, Batteries and ESC board
  • Adding weight via tungsten putty, stick weight, or cut hobby brass is allowed
    • Not Allowed:
    • Prototype parts
  • Public availability requirements:
  • Parts must be publicly announced via social media or website
  • Parts must be available for purchase nationally 45 days prior to race
  • 3D print files must be shared with the public 30 days before event start

More Coming Soon!