Race within the rules
This page explains what governing bodies, regulators, standards bodies and researchers publish. It is not a substitute for your class's rule book, a track's safety rules, the race director or the makers' instructions.
Scale and class
RC racing sorts cars along two lines: what powers them and what they race on. IFMAR, the world body, has an internal combustion (IC) section and an Electric section, and its rule books separate track (on-road) from off-road racing, with the scale (1/5, 1/8, 1/10 or 1/12) naming the class. Wikipedia describes the same split in general terms: electric cars have their motor power regulated by a speed controller, nitro cars carry a small combustion engine, on-road cars race on flat surfaces and off-road cars on rough terrain.
The IFMAR World Championship rule books read for this site cover 1/8 IC off-road (the nitro buggy), 1/8 IC track, 1/10 IC track (a 200 mm nitro touring car), 1/8 IC GT with its electric GTE twin, 1/8 electric off-road (the e-buggy) and 1/10 electric off-road in two-wheel-drive and four-wheel-drive classes. EFRA's 2026 electric appendix covers 1/12, the 1/10 touring car, 1/10 Formula One, 1/10 front-wheel drive, GT12 and 1/10 off-road. Each body's limits apply only at its own events, so they are given here in separate tables. More on the classes themselves is on the classes.
IFMAR World Championship limits
| Class (IFMAR document) | Size limits | Minimum weight and layout |
|---|---|---|
| 1/10 electric off-road (Electric Off Road rules, 13 November 2019, 4.2 to 4.4) | Length 457.2 mm, width 250.0 mm at any point of suspension travel, height 203.2 mm | 2WD 1.474 kg, rear-wheel drive only (front-drive cars run in 4WD); 4WD 1.588 kg, and must be able to finish a lap with either pair of drive-shafts removed. Fixed single-ratio transmission only; reverse not allowed |
| 1/8 IC off-road (2024, 2.1 and 2.2) | Length 550 mm, width 310.0 mm, wheelbase 270.0 to 330.0 mm, height 250.0 mm with roll bar at full compression | 3.2 kg ready to race without fuel for 4WD cars; brakes and clutch must hold the car still with the engine running |
| 1/8 e-buggy (April 2023, 2.1) | Not recorded in this site's research | 3.2 kg ready to race for 4WD cars |
| 1/8 IC track (2023, 5.3 to 5.27) | Wheelbase 270 to 330 mm, width 267 mm, height 180 mm | 2350 g ready to race with empty tank and transponder (5.24). Not allowed: four-wheel brakes, liquid-cooled engines, hydraulic systems, more than two servos, more than three-speed transmissions |
| 1/10 IC track (2024, 5) | A 200 mm touring car | 1650.00 g without fuel, including transponder (5.9), reviewed every two years from the average of standard kits. Four-wheel drive, one brake on the central transmission, at most a 2-speed gearbox |
| 1/8 IC GT (2025) | Length 590 mm, body width 300 to 317 mm | 3500 g with empty tank |
| 1/8 electric GTE (2025) | Not given separately in this site's research | 3800 g |
EFRA limits (EFRA Handbook 2026, Appendix 3)
| Class (section) | Size limits | Minimum weight and layout |
|---|---|---|
| 1/10 touring car (B 7.2) | Width 195 mm with body, 190 mm without; wheel rims at most 50 mm diameter | 1320 g. Independent suspension on all four wheels; a fixed single-ratio transmission, with no multi-speed gearboxes or slipper clutches |
| 1/10 Formula One (B 8) | Width 200 mm | 1050 g on rubber tyres or 1010 g on foam, including personal transponder |
| 1/10 front-wheel drive (B 9) | Width 195 mm | 1250 g including personal transponder. Only the front wheels driven; motor, speed controller and battery inside the bodyshell |
| 1/12 (B 6) | 172 mm wide without the shell (6.2) | 730 g (6.2); the 1/12 GT 17.5 class, which uses GT12 bodyshells, 790 g with body and transponder. Rear end a single solid one-piece axle with no independent suspension (a differential is allowed). The heading of 6.2 extracted as partly garbled text, but its figures read cleanly |
| GT12 (C) | Rolling chassis 165 mm wide; wheelbase 196 to 208 mm | 950 g ready to race with transponder. Chassis shape and hole pattern homologated; chassis metals limited to brass, steel or aluminium |
| 1/10 off-road (D 1 and 2) | Length 460 mm, width 250 mm, height 200 mm with suspension compressed | 2WD 1474 g, 4WD 1588 g (printed as "1.474 gram" and "1.588 gram"); a 4WD car needs effective drive to both axles; any modification allowed; open gears enclosed or protected to prevent injuries |
Where the books disagree
- 1/10 off-road length. IFMAR's 2019 electric off-road rules give 457.2 mm (18.00 in); EFRA's 2026 Appendix 3 gives 460 mm. Both give 250 mm width and the same minimum weights.
- Two weights for cars with GT12 bodies inside EFRA. The 1/12 GT 17.5 class in section B (B 6), which uses GT12 bodyshells and 17.5T motors, gives 790 g with body and transponder, while the separate GT12 technical rules in section C (C 1.2) give 950 g. On a fresh reading of the PDF the two figures sit under two different classes, so they are not two answers for one class.
Rules about how a car may be built to race
Several rules concern the danger a car poses to people, not its speed. They are stated here as each body writes them:
- EFRA Appendix 3, A 12.1 to 12.5: body and chassis must be securely joined whenever the car is on track, driving without a body is never allowed, cars carry numbers in at least three positions, and no car may be built so as to be dangerous or to damage the track or other cars.
- EFRA Appendix 3, A 12.17 and 12.18: bumpers are optional, but if fitted must be built to minimise injury from being hit by a car. The rule sets wire bumpers at 2.5 to 4 mm wire, sheet bumpers at 2.5 to 6.5 mm with rounded edges and closed-cell foam up to 2 cm, and bans rigid blade-like bumpers of metal, brittle plastic or plywood. EFRA's 2024 General Rules (5.3.5) add that technical inspection includes bumpers and protruding parts.
- EFRA Appendix 3, B 1.1: on carpet, a minimum ground clearance of 3 mm for 1/12 and 5 mm for 1/10 at the start of each heat and final.
- IFMAR 1/8 IC off-road (2024, 2.2): a flexible plastic front bumper with no metal and rounded edges is mandatory, to limit damage on contact with other participants, marshals or anyone else.
- IFMAR 1/8 IC track (2023, 5.8): a flexible front bumper protruding no more than 5 mm ahead of the body.
- IFMAR Electric Off Road (2019, 4.2): one car per driver per class; the chassis is marked at technical inspection and may only be replaced, with the race director's approval, by one of the same design after damage that cannot reasonably be repaired.
Driver aids the rules ban
EFRA's Appendix 3 (A 4.1 and 4.2) bans automated steering, gyroscopes controlling the car's movement, traction control and active suspension, and bars using the receiver to capture signals from sensors in the car. IFMAR's electric off-road rules (2019, 4.5) ban traction control, active suspension, gyroscopic steering control, sensors measuring suspension, wheel speed or tyre slip, and active telemetry. IFMAR's 1/8 IC off-road book (2024, 2.8) bans traction control, active suspension and gyro-aided steering, allowing sensors only for passive data recording, and says the World Championship is meant to test driver skill.
ROAR and the BRCA
ROAR's current rule book was not read for this site. Its rule book update of 18 October 2024 says rule 8.5.13 requires shock protectors on off-road cars racing on carpet, and that on carpet no vehicle's drive axles may extend beyond the wheel nuts. No other ROAR chassis limit is recorded here. The BRCA's 2026 section rules were not read either, so no BRCA chassis limit is given; see the BRCA and national bodies.
Sources
- IFMAR, Electric Off Road Racing and Technical Rules, version 13 November 2019
- IFMAR, 1/8th I.C. Off-Road Racing and Technical Rules (2024, amended March 2024)
- IFMAR, 1/8th I.C. Track Racing and Technical Rules (2023, amended March 2023)
- IFMAR, 1/10th I.C. Track Racing and Technical Rules (2024)
- IFMAR, 1/8th 4WD I.C. GT and electric GTE Track Rules 2025 (amended 30 April 2025)
- IFMAR, 1/8th E-buggy Off-Road Racing and Technical Rules (April 2023)
- EFRA Handbook 2026, Appendix 3, Electric Cars (v4, June 2026)
- EFRA Handbook 2024, General Rules
- ROAR, rule book update (18 October 2024)
- Wikipedia, Radio-controlled car (secondary)