2023 F1 testing — tyre compounds and Pirelli's black-walled prototype

Teams may be disguising their true pace but we can begin to glean one or two details from the timing sheets by taking into account lap counts and importantly, tyre compounds used for those laps.

When racing begins, you’ll only see teams running the familiar white hard tyre, yellow medium and red soft (in addition to wet weather compounds) because only three compounds, selected from the full range of six, are used on a race weekend. These vary depending on the circuit.

The hardest is assigned the white band, the softest the red band and the middle compound has the yellow band.

With all six available to teams during testing, some of them look a little different. Here is the Pirelli range in use in Bahrain for F1 pre-season testing:

2023 F1 Bahrain testing slick tyre compounds

Pirelli C0 compound

The hardest compound in Pirelli’s range, the C0 tyre has a new name but the same specification as last year’s C1. It features white markings on the tyre wall but does not have the usual band of colour along with it for testing. The compound provide maximum resistance to heat and extreme forces, enabling long stints at the cost of peak performance. It will only be used at circuits that take most energy out of the tyres, so won’t feature in any of the opening three rounds.

Pirelli C1 compound

Pirelli’s new compound is a bit softer than the C0 but harder than the C2, filling the performance gap between those two tyres which Pirelli thought was too wide. It also has white markings, but this time with the usual colour band along with the Pirelli logo. The C1 will be the hard tyre for the first race, also at Sakhir.

Pirelli C2 compound

Pirelli says that what is now the third-hardest tyre in its range is suited to faster, hotter and more abrasive circuits. Its first race appearance will be as the medium tyre in the Bahrain Grand Prix. A lick of paint later, it will become the hard compound in Saudi Arabia.

Pirelli C3 compound

Pirelli’s middle compound can act as the softest or hardest at a race weekend depending on the selection available to teams. Indeed, it will be the soft tyre for the opening race in Bahrain before featuring the yellow bands it carries in testing as the medium tyre in the Saudi Arabian and Australian Grand Prix.

Pirelli C3 Proto compound

These prototype tyres will be unmarked, so are easily distinguishable from the rest of the range. They are intended to be identical to the usual C3 compound but are manufactured at Pirelli’s backup Turkish base rather than its main Romanian factory. They are run to benchmark production quality.  Teams will be supplied with two sets of these tyres for testing.

Pirelli C4 compound 

The second-softest compound, the C4 warms up quickly and offers improved grip, but is most effective on tracks with low degradation to avoid a rapid drop-off in performance. The C4 will be the soft tyre in Saudi Arabia and Australia.

Pirelli C5 compound

The C5 is the softest compound of tyre in the Pirelli range. Cars should be flying on these tyres, so don’t read too much into the testing times if a C5-clad car tops the timing sheets while everyone else is on the C2. The tyre is only usually selected on extremely smooth surfaces or on street circuits that demand maximum mechanical grip (such as Monaco), so won’t appear in the first three races of the year.