WRC Rally tyres [2021 update]
It’s been almost 4 years since our previous article on WRC tyres and plenty of things have happened since then. From the first WRC champion not named Sébastien — Ott Tänak in 2019, to new regulations and a corona stricken season 2020 with many cancellations, which crowned Sébastien Ogier as champion for the 7th time. As we are getting closer to the next season, we can only hope that 2021 will have more mercy on the championship calendar and we’ll finally see the long awaited return of the two iconic rally venues — Kenya and Japan.
However there is one return that we are already certain of, the comeback of Pirelli as the exclusive tyre supplier for the first time since 2010. Since then Pirelli wasn’t that far away from the WRC, as it has continued to supply the Rally2 (R5) cars category, while also being an exclusive supplier for the Junior World Rally Championship since 2018, but the company made sure that their tyres are ready for the season, by appointing Andreas Mikkelsen as their test driver in a Citroen C3 WRC, who put their tyres to extreme on gravel and tarmac roads of Sardinia.
The season 2021 will include diverse surfaces ranging from ice on the curvy roads of Rallye Monte Carlo to notorious Kenya, smooth Spanish tarmac to high-flying Finland forests.
So what are the tyre models that WRC drivers will use?
PIRELLI PZERO RA
Designed for use on dry or damp asphalt.
Suitable for: Rally Spain, Rally Croatia, Rally UK*
*if switched to tarmac as rumoured
PIRELLI CINTURATO RWB
Designed specifically for wet asphalt surfaces
Suitable for: any tarmac rally in extremely wet conditions.
PIRELLI SCORPION KX
Versatile tyre for best performance on hard or soft gravel surfaces.
Suitable for:
Rally Sardegna, Rally Portugal, Rally Chile, Rally Estonia, Rally Finland, Rally Kenya, Rally Japan.
PIRELLI SOTTOZERO STZ B
Designed for mixed conditions of snow/ice and tarmac. Can be used with or without studs.
Suitable for: Rallye Monte Carlo
PIRELLI ICE SOTTOZERO J1
Fully studded tyre, designed for fully snow / ice surfaces.
Suitable for: Rally Sweden
Just a recap on the tyre regulations:
60.1.2 All cars must be fitted with moulded tyres. Hand cutting or modification of the specified tread pattern is not permitted. Only marked tyres may be used on special stages.
60.1.3 Any chemical and/or mechanical treatment of tyres is prohibited. Any device for heating the tyres once fitted on the rim is prohibited. Whether fitted on rims or not, keeping tyres in an artificially heated environment below 35°C is allowed.
60.1.4 Each tyre must have either:
– Two identical moulded barcode numbers (one on each side of the tyre / each barcode having a different colour as defined by the FIA) supplied by the FIA‐approved barcode supplier, or:
– A single moulded barcode number supplied by the FIA‐approved barcode supplier. These barcodes will be used to check that the same tyres remain fitted to a particular car between tyre changes and that competitors are not exceeding the maximum quantities allowed. The tyre barcode must always be visible from outside the car.
60.1.6 The use of any device for maintaining the full performance of the tyre with an internal pressure equal to or less than atmospheric pressure is forbidden. The interior of the tyre (the space between the rim and the internal part of the tyre) must be filled only with air.
60.1.7 Any device designed to clamp the tyre to the rim is not permitted.
60.1.8 The maximum pressure for fitting the tyre onto the rim is 8 bars at 20°C; this pressure must allow the tyre to stick to the outer walls of the rim.
60.1.9 At all times during the event, the tread depth of the tarmac tyres fitted on the car must not be less than 1.6 mm over at least three quarters of the tread pattern. The tyre manufacturer must provide visible control marks.
Special rules apply to studded tyres:
– the studs shall be solid, cylindrical and flatcut, cross section of the studs must form a full circle at every point, studs are not allowed to be tubular, body of the stud must be homogenous and must not form a tube or hole, maximum diameter of the flange is 9mm, while minimum diameter of the metal core in the middle, length of the stud is limited to 20mm and weight to 4grams, must be mounted from the outside and studs must not exceed 20 per decimeter of the wheel circumference.
How are tyres allocated?
Prior to scrutineering at each rally, each tyre company will provide the FIA with a list of barcodes on the basis of which there will be a random procedure (lottery) for the selection of the tyres, overseen by the FIA. Following this selection procedure, the FIA will supply the Manufacturer or WRC Team with a list of barcodes of the tyres that may be used by each driver entered. A driver may only use a tyre that has been registered for his car.
How many tyres can a driver use in a rally?
The quantities of new tyres for use at each Championship event shall be detailed in the rally supplementary regulations and be based on the following:
– A maximum of 7 tyre changes is permitted on any one rally.
– The maximum quantity of tyres allowed on each rally will be calculated as follows: “X” number of changes multiplied by 4 tyres. In addition, 4 tyres for WRC cars and 2 for the other cars are added in the overall quantity. For the Monte Carlo rally, the “X” number of changes will be multiplied by 5 tyres.
– Tyres used during the Shakedown will not be included in the overall quantity allowed for the rally, but must be from the same compound.
– Cars may carry a maximum of two spare wheels.
Example quantities in 2020:
- Rally Sweden: 24 tyres (studded) + 6 for shakedown = 30 in total
- Rally Monte Carlo: 80 tyres allocated (20 soft, 24 super soft, 12 snow non-studded, 24 snow studded), but maximal quantity that can be used is 38 in case of rally with shakedown and 34 without shakedown.
- Rally Estonia: 16 tyres (+4 for shakedown)
- Rally Italy: 24 tyres (+4 for shakedown)
Rims must imperatively be made from cast material. Forged rims and rims manufactured using flow forming process are forbidden. Material: magnesium or aluminium alloy.
For gravel rallies, only 7” x 15” rims are authorised and the minimum weight of a rim is 8.6 kg.
For asphalt rallies, only 8″ x 18″ rims are authorised and the minimum weight of an rim is 8.9 kg.
So, that’s a quick view into WRC tyre regulations, feel free to share this around and stay tuned for our next articles about gearbox types, differentials and many other tutorials.
Credits:
– Image credits Pirelli.com, for illustration purposes only
– Rules from Appendix J 2020 and WRC Sporting Regulations 2020
– Data from individual events from their supplementary regulations
– WRC Rally cars for sale
