New Rally1 technical regulations and aero trimming

The publication last week of the approved specific Technical Regulations for Rally1 Cars (Article 262 of 2022 Appendix J) brings some light into the aero configuration of the new cars. There were expectations of knowing how far the trimming would go, after all the information previously released by FIA and its representatives, which we compiled here. And the new regulations clarify some points, while still, some others remain unclear, due to lack of information. This is our review of what is defined in these regulations… and what is not.

As expected, the new regulations confirm the important step backwards in terms of aero. The goal was clear, in order to reduce costs and speed. The first step can be found in the form of parts banned by the new regulations: rear diffuser, fender vents and louvres.

However, to compensate for the loss of the rear diffuser, the rules specify a maximum angle of 8° to the reference plane for the rear protection, the one located between the rear differential and the rear bumper. It is the same location where the diffuser was in the 2017 WRC cars.

Image extracted from FIA Appendix J 2022 – Article 262 – Specific regulations for Rally1 Cars- WMSC 15.12.2021

From the images of the development tests of the new cars, Toyota seems to be the only team taking advantage of this point, as the rear protection of the Yaris is the one with a higher angle.

E.Evans/S.Martin, Toyota GR Yaris Rally1, development tests in France, September 2021 – image by Louka Sorriani

The use of a flat floor is also compulsory between the front and rear wheels. Design is free, and it can contain openings for heat extraction from the exhaust system.

The use of cooling ducts in bumpers and wheel arches continues to be allowed. This means that also venting ducts are allowed, with the only limitation that the wheel must not be visible through the openings homologated in the rear bumper (in all directions and for any wheel position). And that openings may be fitted with wire netting with a mesh of maximum 10 mm, but no louvres. Again, Toyota is the only manufacturer to take advantage of this point, as the GR Yaris Rally1 is the only car with brake venting ducts connected to the rear bumper (a), at the present moment.

S.Ogier/B.Veillas, Toyota GR Yaris Raly1, Development tests in France, December 2021 – image by Frédéric Mangeant

The introduction of the hybrid system is one of the main novelties in the new regulations, with important impact on the aerodynamics of the cars. The electric engine and the batteries have been included in the list of items that can be cooled, for what homologated openings are allowed in the rear door panels, to feed fresh air for cooling purposes.

C.Breen/P.Nagle, Ford Puma Rally1, Development test in Spain, October 2021

For the cooling of other elements, air ducts remain allowed in the front bumper, with the only condition that can only be used to cool the auxiliaries (certain parts of the car defined in the regulations), and only one duct per auxiliary is authorised.

T.Neuville/J.Vial, Hyundai i20 N Rally1, Development tests in Frace, December 2021 – image by Julien Pixelrallye

Regarding the homologated openings for engine and cockpit cooling, they still can be partly or completely sealed by adhesive tape or screen as with the previous car generation.

But that’s all. There is no mention of other forbidden parts, such as dive planes or winglets on top of the fenders. And don’t look for any other information about dimensions, shape, frontal projection or location of the rest of the aero parts (wing, fenders, roof scoop, side skirts,…). The only reference is the Rally1 Homologation Form, which is not public.

Dimensions and weight

The regulations set the maximum dimensions of the car, by setting the volume where the outer surface of the Rally1 bodywork may be within the envelop generated by the outer surface of the series production part, as shown in the images below.

Image extracted from FIA Appendix J 2022 – Article 262 – Specific regulations for Rally1 Cars- WMSC 15.12.2021

The areas in red are the areas where aero parts can be located, always inside the dimensions set in the figures.

Image extracted from FIA Appendix J 2022 – Article 262 – Specific regulations for Rally1 Cars- WMSC 15.12.2021

The image above contains the maximum width of the car (1875 mm), all elements involved. The minimal height is set at 1250 mm, understood as the distance between the plane of reference (the plane passing through the lowest point of the RALLY1 chassis) and the highest point of the roof panel.

There are no changes with respect to ground clearance: as with previous car generation, the ground clearance has to ensure that no part of the car must touch the ground when all the tyres on one side are deflated. This test must be carried out on a flat surface under race conditions (occupants on board).

Other dimensions set by the new regulations are the max dimensions of the rear view mirrors. Two external mirrors are compulsory.

Image extracted from FIA Appendix J 2022 – Article 262 – Specific regulations for Rally1 Cars- WMSC 15.12.2021

The max dimensions the rear view mirrors (that must be fixed on the door panel) can have is also set by the new regulations. The shell containing the mirror may only be extended to the door panel by means of a structure that does not contain any opening and only inside the volume identified in the above drawing (example of left-hand side rear-view mirror). The maximum length (L max in the drawing) is fixed at 100mm, while the max radius (R max) is set at 200 mm.

Each rear-view mirror must have a reflecting surface of at least 90 cm², and it can contain a cut-out (max surface 25 cm² per mirror) in the housing for cockpit ventilation.

The minimum weight is 1.260 kg under the checking conditions (against 1.190 for the 2017 WRC cars), with just one spare wheel. With the crew (driver and codriver) the minimum weight increases up to 1.430 kg (1.360 for 2017 WRC cars).

Homologation of new parts (jokers)

In 2021, the prohibition of not using an old part as from the date the new part was homologated was removed. In the new 2022 regulations, this prohibition is effective again, thus manufacturers will be forced to use homologated parts since the date of homologation, not being able to turn back to older pieces.

New radiator specifications

The new regulations also include the specification for radiators. Any liquid/air radiator made of more than one tube must comply with the following conditions:

radiator core must have a max of 6 flat faces

radiator core must be tube and fine design

each row of coolant tubes must have a max of 18 tubes per 100mm (see drawing below).

Image extracted from FIA Appendix J 2022 – Article 262 – Specific regulations for Rally1 Cars- WMSC 15.12.2021

The minimal internal dimension of radiator tubes is 0.8 mm.

In summary, the new regulations confirm the trimming of important aero parts, while others remain unclear. Some of the lacking parts have been replaced by new solutions proposed by the teams, but the impact on performance will be, in our opinion, sensitive, especially in the corners.

But the new rules also represent another missed opportunity to share all the details of the new rules with the public, whereas in other motorsport disciplines (from F1 to NASCAR) they are made public months before they are implemented. It would be nice to have the same access in rallying. The higher the information provided, the more you can understand and enjoy a competition where technique plays such an important role. But again, it will not be the case in 2022. Perhaps this is an opportunity for the new FIA management team to improve.


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5 thoughts on “New Rally1 technical regulations and aero trimming

  • 2021-12-20 at 15:59

    Thanks, a very useful commentary as always. With no return to earlier homologation specs, what Toyota did last year, reverting to earlier heavier homologation specs for the suspension for the Safari will not be possible. Manufacturers must now have one spec, both for rough and smooth gravel rallies, and for tarmac. This suggests they will be conservative and go with a heavy duty spec that can handle all rallies, so we may see Manufacturer cars in Monte Carlo using Safari Spec suspensions.

    • 2021-12-20 at 18:40

      Thank you, Lawrence. Yes, no chance to come back to previous designs now, as in the period 2017-2020. Last year was a kind of special situation, as new homologated cars were postponed to 2022.

    • 2021-12-21 at 01:44

      When you guys speak about ‘homologated suspsension’ my mind keeps going back to Adamo’s departure from Hyundai… even though I’m sure he has NOTHING (*wink*-*wink*) to do with his cars keep failing in that one area.

  • 2021-12-21 at 05:40

    Thank you for this excellent analysis. It’s a shame, this new regulation is much more restrictive for research !

    • 2021-12-21 at 20:59

      Thank you Jean Luc for your kind words. Yes, they are more restrictive, but sometimes this is good for stimulating the imagination of engineers.


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