Motors

Motors: the 05 brushless can, Modified and Spec, body by body.

Many of EFRA's electric classes are named by the motor a car may carry. EFRA and IFMAR both approve only brushless motors of one standard size for 1/12 and 1/10, and split them into Modified and Spec. This page sets out what each body's rule says, and where the two differ. It is a description of the rules, not a setup or tuning guide.

Disclosure: this page has affiliate links. If you buy through them, we may earn a commission at no extra cost to you. As an Amazon Associate we earn from qualifying purchases. How this works.

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.

The terms the rules use

05 size: EFRA's name for the standard brushless motor can used in 1/12, 1/10 touring car and 1/10 off-road (EFRA Handbook 2026, Appendix 4, sections 4 and 5). IFMAR's March 2023 batteries and motors document uses the same "05" label and approves only that size for these classes.
Turns (for example 13.5T or 17.5T): EFRA's rules use this for the number of winding turns on a Spec brushless motor's stator. The trade magazine RC Car Action (Peter Vieira, updated 15 August 2016) describes a turn as one wrap of wire around the stator and says more turns generally means lower RPM, so a 17.5T motor is slower than a 10.5T.
Modified and Spec: EFRA's two types of homologated brushless motor (Appendix 4, 4.1). Modified motors may be sensored or sensorless and have no turn limit. Spec motors must be sensored and have fixed turns.
Kv: A maker's rating, not a rule. RC Car Action describes it as a motor's unloaded RPM per volt (its example: a 2200Kv motor should spin about 2,200 RPM on one volt, and less under load), and says makers indicate a motor's level either by turns or by Kv, depending on the brand. No rule book read for this site sets a Kv limit.

The 05 motor, EFRA and IFMAR side by side

Both bodies set the same can size. Each column below is that body's own rule; neither applies at the other's events.

Point	EFRA Handbook 2026, Appendix 4	IFMAR Batteries and Motors, March 2023
Which motors may race	Only motors on the EFRA homologation lists, at European Championship and Grand Prix electric events (section 5)	Only IFMAR-approved 05 brushless motors at its electric World Championships; commercially available four months before the event (section 4)
Can size	Diameter 34.00 to 36.02 mm, length 50.0 to 53.0 mm, mounting holes on 25.0 to 25.4 mm centres (4.3 to 4.7)	Diameter 34.00 to 36.02 mm, length 50.00 to 53.00 mm (6 and 7)
Stator	19.30 to 21.00 mm long; laminations 0.35 mm, plus or minus 0.05 mm, of one material (4.9)	19.30 to 21.00 mm long (6)
Modified windings and rotor	Delta or Y in round pure copper, no turn limit (classes may set a minimum); one-piece two-pole neodymium or ferrite rotor, 3.175 mm shaft (4.10 to 4.12)	Delta or Y, no turn limit (classes may set a minimum); two-pole neodymium or ferrite rotor, 3.175 mm shaft; magnet 23.00 to 27.00 mm long (6)
Spec windings	Sensored, Y (star) wound only, fixed turns and wire diameters per class, for example 17.5 turns of two 0.813 mm wires (4.13 to 4.17)	Y-wound only, fixed turns and maximum wire diameters per class (7)
Spec magnet	25.00 mm long, plus or minus 1.00 mm; 12.20 to 12.51 mm diameter	24.00 to 26.00 mm long; 12.20 to 12.51 mm diameter
Spec classes listed	21.5T, 17.5T, 13.5T and 10.5T	13.5T, 17.5T, 21.5T and 25.5T
Marking	Maker's name or logo in the end bell; wind number etched on motors introduced from 2011	Wind number etched on the outside of the motor

EFRA also says its 05 motors must be rebuildable, may not be hybrids of different makers' parts and may not be modified, and that sensored motors use a six-position JST ZH connector with a fixed pin order (4.2 to 4.7). EFRA says its Spec rules were agreed by various international organisations.

Where they differ

The Spec wind lists. EFRA's 2026 Appendix 4 (4.15) lists 10.5T but not 25.5T; IFMAR's March 2023 document lists 25.5T but not 10.5T.
The date EFRA's lists began. Inside EFRA's own handbook, Appendix 3 and section 4 of Appendix 4 say homologated motors were required "from May 2016", while section 5 of Appendix 4 says "starting 01.06.16".
IFMAR's Spec approvals. One passage of IFMAR's March 2023 document (4.5) says that until further notice IFMAR does not approve Spec motors but will start listing them from 2023. The wording is ambiguous, and this site does not say which reading is right.

Which motor each EFRA class uses

EFRA's 2026 Appendix 3 (A 7.1.1, B 6 and C 3) names the motor for each European Championship class:

EFRA class	Motor
1/10 off-road, 2WD and 4WD	Modified
1/12 Modified	Brushless of no less than 6.5 turns, with a "blinky" speed controller
1/12 Spec	13.5T Spec brushless, blinky
1/12 17.5T class	Any 17.5T motor on the EFRA Spec list, with a zero-boost (blinky) speed controller from the approved list
1/10 touring car	Modified, or 13.5T Spec brushless in the Spec class
1/10 Formula One	21.5T Spec brushless
1/10 touring car FWD	21.5T Spec brushless, blinky
GT12	A 13.5 Spec or 17.5 Spec motor from the matching EFRA list; one drive motor per car (C 1.22)

EFRA Appendix 3 (A 11.5) also lets an EFRA-appointed person dismantle and check the motors of the top three finishers after a race. The "blinky" requirement is explained on speed controllers.

Larger motors: 1/8 electric

EFRA's 2026 Appendix 4 (section 6) gives 1/8 electric motor rules that it says were agreed with IFMAR from 2025: a can at most 77.0 mm long and 44.0 mm in diameter, at most 12 stator slots, and a 5.0 mm shaft at the pinion; from 1 January 2026 every rotor must have its part number marked on the shaft. IFMAR's April 2023 e-buggy book (2.2) limits the can to 77.00 mm long, sets mounting holes on 25.40 mm centres and limits the stator to 39 mm outside diameter. The two measure different things (the whole motor against the stator), so they are not a contradiction as written.

ROAR's dated changes

ROAR's current rule book was not read for this site, so its motor classes are not given. Its rule book update of 18 October 2024 records these changes:

Rule 11.3.1.4: motors with epoxy-coated stators stay on the ROAR Approved List until 31 December 2026, while motors to a new specification are legal from 1 September 2025, a 14-month overlap.
Rule 11.3.7.10: makers could submit new-specification motors from 1 January 2025, and motors approved before 1 September 2025 have a four-year term ending 31 August 2029.
Rule 11.3.5.7: the largest allowed motor cooling fan rose from 30 mm to 40 mm in diameter.
Rules 1.8.1, 11.11.1 and 8.3.7: the GT12 and LMH specifications no longer name a motor wind; track owners and race directors choose the wind for each class.

Brushed motors

No current racing rule book read for this site sets a limit for brushed motors. EFRA and IFMAR approve only brushless motors for the electric classes covered here. The BRCA's 2026 motor rules were not read. For how the motor came to be brushless, see motors and batteries history.

Gear for thisBrushless motors →Speed controllers →

Sources

Keep reading

Speed controllers

The electronic speed controller as rules define it: EFRA's zero-timing profile and its Approved Blinky ESC list, IFMAR's connector and control-device limits, ROAR's firmware and blinky-mode rules, and the aids every book bans.

Approved equipment lists

Every approved list the research found, body by body: EFRA's motor, battery, blinky ESC, bodyshell and muffler lists with their deadlines, IFMAR's yearly World Championship lists, ROAR's Approved List and who is responsible for it, and what was seen only by title.

Batteries

Lithium polymer and lithium iron phosphate packs as racing rules name them: cell counts, nominal and charged voltages, hard cases, labels and UN 38.3, which classes use 1S, 2S and 4S, and the fire hazard as OSHA, UL and the CPSC describe it.