The FIA Appendix K Technical Regulations relating to tyres (paragraph 13) state:
“The nominated tyre for HFO is the Avon A11 compound cross ply tyre and only these may be used. For wet weather use only Avon race tyres of standard wet weather pattern may be used. Not more than one set of slick tyres (4/6) may be introduced at each event. Category ‘G’ cars may use Dunlop treaded tyres using a CR65 tread pattern.
The use of any tyre warming device, or the application of any artificial compound, which may affect the hysterisis of the tyre tread, is strictly forbidden.”
Please note that “each event” includes the free practice session, generally on Friday.
Only one set of slick tyres per weekend will be marked up by the Technical Delegate. Ideally used tyres fitted to cars during the event should bear the marking from a previous HFO event although that may not always be practicable.
However it is the responsibility of the team to be sure they have sufficient “obviously used” slick tyres to supplement the introduction of one set per event. If there is any doubt, the final decision on the condition of a tyre will rest with the Technical Delegate.
The FIA Appendix K Technical Regulations relating to instrumentation (paragraph 6) state:
“Electronic instrumentation may be fitted but any data acquisition of that instrumentation must be limited to the following functions, engine RPM, engine oil pressure, engine oil temperature, engine water temperature and fuel pressure.
Wheelspeed sensors may be used during private testing only and must be removed from the car for the duration of the TGP (HFO) event including untimed free practice.