Teams may disguise their true pace in testing 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. So on race weekends at tracks where tyre wear is high, Pirelli brings harder compounds: the most commonly-seen C3 is often the softest compound available. In this scenario it will feature red markings.
In other locations, it features as the medium tyre with yellow markings, sitting between a harder and a softer compound. And when F1 races at circuits with lower cornering speeds and less tyre degradation, the C3 may be the hardest compound that Pirelli brings, so it will feature white markings.
2025 F1 Bahrain testing slick tyre compounds
Pirelli C1 compound
Pirelli C1 compoundThe hardest compound in Pirelli’s range, the C1 tyre features white markings on the tyre wall but does not have the usual band of colour along with it for testing. The compound provides 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.
Pirelli C2 compound
Pirelli C2 compoundPirelli has updated the C2 to be closer to the mid-range C3, offering more performance but a little less durability than last year’s version. It also has white markings, but this time with the usual colour band along with the Pirelli logo.
Pirelli C3 compound
Pirelli C3 compoundThe most commonly-used tyre in the Pirelli range is also likely to be the most used in testing. The third-hardest tyre in its range is described as the most versatile in terms of balance and degradation and is largely unchanged from previous seasons
Pirelli C4 compound
Pirelli C4 compoundPirelli’s middle compound can act as the softest or hardest at a race weekend depending on the selection available to teams. It’s compound has been revised in an attempt to improve resistance to small tears that open up as the tyre slides along the track surface – known as graining – which can result in a significant performance loss.
Pirelli C5 compound
Pirelli C5 compound The second-softest compound, the C5 warms up quickly and offers improved grip, but is most effective on tracks with low degradation to avoid a rapid drop-off in performance. Its resilience may be improved this year, with an updated compound that, like the C4, should be better at resisting graining.
Pirelli C6 compound
Pirelli C6 compoundNew for 2025, the C6 is the softest compound of tyre in the Pirelli range. If you do see it on track on a Williams or Haas, they’ll likely be flying on these tyres, so don’t read too much into the testing times if a C6-clad car tops the timing sheets while everyone else is on the C2. The tyre is too fragile for the high cornering speeds on most circuits, so expect it to be seen at circuits such as Singapore, Montreal and Monaco where corners are generally taken at slower speeds.