​The Belgian Grand Prix runs this weekend at Spa-Francorchamps, the longest lap in Formula 1 and the penultimate round before the summer break. Pirelli has nominated the C2, C3 and C4 compounds, the harder end of its range, for a circuit that punishes tyres through sustained high-speed loads, and the supplier’s own preview points to rising track temperatures and a genuine chance of two-stop strategies. Here is everything worth knowing before lights out, from the tyre nomination to the microclimate, plus the numbers behind the strategy calls.Spa-Francorchamps Circuit length: 7.004km, the longest of the season, with the calendar’s greatest elevation change and 19 corners.Tyre nomination: C2 (hard), C3 (medium), C4 (soft), the harder end of Pirelli’s range.The circuit was fully resurfaced two years ago and typically offers low grip early in the weekend, though June’s 24 Hours of Spa has laid extra rubber this time.Track temperatures at that 24-hour race exceeded 55 degrees, and Pirelli expects higher thermal degradation if the heat returns, raising the odds of two-stop races.Spa hosts the cheapest pit stop in Formula 1, a measured 18.4 second median cost, which lowers the bar for a second stop further than any circuit on the calendar.AdvertisementAdvertisementAdvertisementPirelli’s nomination brings the C2, C3 and C4 to a circuit it rates among the most demanding for tyre loads, short of only the Suzuka and Silverstone class. The supplier expects the two hardest compounds in the range to carry Sunday’s race, and flags that if track temperatures approach the 55-degree-plus values seen during June’s 24 Hours of Spa, thermal degradation will climb and two-stop strategies become realistic.That expectation collides with this season’s strangest measured finding. The 2026 tyre degradation data shows the hard compound wearing fastest and the soft slowest, the first inversion of the hierarchy in the ground-effect era, because the lighter, lower-downforce cars struggle to bring hard rubber into its working window. Spa’s sustained loads through Pouhon and the Eau Rouge climb are the best energy source the hard tyre has been offered all season. If Pirelli’s hard-compound race unfolds as expected, this weekend doubles as the sternest test yet of whether the inversion survives contact with a genuine high-load circuit.Any two-stop temptation gets a helping hand from the pit lane itself. Spa hosts the cheapest pit stop in Formula 1, an 18.4 second median cost across five seasons of measured data, because the lane bypasses the La Source hairpin complex. And once a team commits to stopping, the undercut succeeds 71 percent of the time here, the most reliable strike rate of almost any circuit measured. Cheap stop, dependable undercut, and a supplier openly predicting elevated degradation: if the one-stop pattern that has defined 2026 breaks anywhere, the ingredients are all on the table this weekend. The full strategic picture, circuit by circuit and number by number,