[1] The formula for Group Rally4 cars was taken from R2 class of Group R and tweaked with the defining ruleset interchanging the terms, this meant that any existing R2 car homologated or approved since their introduction in 2008 could continue to be used in Rally4 level competition.

[2] However, R2 cars homologated prior to 2019 were not required to have a turbo restrictor fitted and remain exempt.

Those of R2B class cars also retain the minimum weight of 1030 kg and must use 6.5"x16" on asphalt rallies.

[3][4] Group Rally4 cars are defined in FIA document Appendix J - Article 260 as Touring Cars or Large Scale Series Production Cars, supercharged Petrol engine (including rotary engines), 2-wheel drive (front or rear wheel drive)).

[1] legacy class) Weight Capacity Cylinders Restrictor Gravel Asphalt Requirement or 7"x17" Rally4 cars are placed in FIA 'RC4' sporting class alongside R3 and Group A cars.