F1 Intermediate Tyres Explained
"Box for the inters" is one of the calmer calls on team radio compared to what usually follows it — a scramble to read a track that's neither wet enough for full wets nor dry enough for slicks. The intermediate tyre is Pirelli's answer to that gray zone, and understanding its tread, its water-clearing limits and its crossover point explains why so many rain races are actually run entirely on green tyres.
F1 Intermediate Tyres by the Numbers
- 3mm: tread depth on the intermediate tyre, versus 5mm on the full wet.
- ~2mm: the standing-water depth up to which the intermediate is the preferred tyre before a full wet becomes necessary.
- ~30 L/s: Pirelli's rated water-displacement figure for intermediates at 300 km/h.
- ~85 L/s: the equivalent figure for full wets, our Pirelli F1 tyres guide covers the full compound range.
- 4 / 3: intermediate and full-wet sets, respectively, allocated per driver on a standard weekend.
- 25mm / 30mm: how much narrower the 2026 wet-weather tyres run at the front and rear versus the previous generation, matching the smaller 2026 car dimensions — the tread pattern itself is unchanged from 2025.
- 3 laps: the entire distance of the 2021 Belgian Grand Prix, the shortest race in F1 history, run behind the Safety Car and red-flagged before cars ever got a genuine green-flag lap in the rain.
- 2 laps: the new minimum for points to be awarded, a rule the FIA introduced directly because of that race.
What Are Intermediate Tyres?
Intermediate tyres carry a green sidewall marking and sit between the dry compounds and the full wet in Pirelli's range. They're designed for a track that's damp, drying, or lightly wet — conditions where a slick would have no grip but a full wet's deeper tread would generate excess heat and actually go off faster on a track that isn't saturated. The tread pattern combines circumferential and lateral grooves to channel a moderate amount of water while still generating enough mechanical grip on surfaces that are only partially covered.
Tread Depth and Water Clearance
The intermediate's 3mm tread depth is shallower than the full wet's 5mm, a deliberate trade-off: less tread means less flex and heat build-up on a track that isn't fully saturated, but also less capacity to clear standing water. Pirelli rates the intermediate to displace roughly 30 liters of water per second at 300 km/h, effective for standing water up to around 2mm deep — beyond that, the shallower tread can't clear water fast enough and the car starts to aquaplane. The full wet's deeper tread and roughly 85 liters per second rating exist specifically to cover conditions past that threshold.
The Crossover Point: When Teams Switch
The "crossover point" is the moment track conditions tip in favor of a different compound — slick to intermediate, intermediate to full wet, or back again as a track dries. It isn't a fixed rulebook number; teams read it from a mix of trackside rain sensors, driver radio feedback about grip and spray, and their own tyre data, then gamble on the timing of a pit stop. Because both the intermediate and full wet compounds carry new specifications for 2026, teams went into the season expecting the crossover points themselves to shift versus prior years, even though this year's tread patterns are unchanged from 2025 — meaning some of the pre-season simulator work on wet-tyre timing had to be redone from scratch.
| Tyre | Color | Tread Depth | Water Displacement | Typical Trigger |
|---|---|---|---|---|
| Slick (dry) | White / yellow / red | ~1.6mm | None — bald tread | Dry track |
| Intermediate | Green | 3mm | ~30 L/s | Damp track, up to ~2mm standing water |
| Full Wet | Blue | 5mm | ~85 L/s | Standing water beyond ~2mm |
Why Full Wet Tyres Rarely Race
In theory, the full wet tyre exists for heavy rain. In practice, it's one of the least-used tyres on the calendar, because a car throwing up enough spray to need it is usually also throwing up enough spray that the driver behind literally can't see. Race control's response to that visibility problem is almost always a red flag or extended Safety Car period, which halts the session before conditions ever get bad enough to justify a switch away from intermediates. The clearest example is the 2021 Belgian Grand Prix at Spa: after a rain delay of several hours, cars ran just three laps entirely behind the Safety Car before officials abandoned the session for the day, making it the shortest race in F1 history without a single genuine green-flag racing lap. The farce prompted a rule change — a race now needs at least two completed racing laps for points to be awarded, with a reduced 6-4-3-2-1 scale for the top five if the race ends under 25% distance. Our F1 flags guide covers how red flags and Safety Cars work in more detail, and our Virtual Safety Car explainer covers the lighter-touch alternative race control reaches for first.
Frequently Asked Questions
What do green tyres mean in F1?
Green sidewall markings identify intermediate tyres, Pirelli's crossover compound for a damp or drying track that's too wet for slicks but not wet enough for the deeper-treaded full wet tyre. They cover the middle ground between the white/yellow/red dry compounds and the blue full wet tyre.
How much water can F1 intermediate tyres clear?
Pirelli rates the intermediate tyre to clear roughly 30 liters of water per second at 300 km/h, suited to standing water up to about 2mm deep. The deeper-treaded full wet tyre is rated at roughly 85 liters per second for conditions beyond that.
Why don't F1 teams use full wet tyres more often?
Full wet tyres are built for heavy rain, but the spray a modern F1 car throws up at speed cuts visibility so badly that race control typically red-flags a session for safety before conditions ever justify switching off intermediates. The 2021 Belgian Grand Prix, which never completed a genuine racing lap because of exactly this problem, is the clearest example.
How many sets of intermediate tyres does each driver get?
A standard Grand Prix weekend allocates 4 sets of intermediate tyres and 3 sets of full wets per driver, on top of the separate 13-set dry-tyre allocation.
The Bottom Line
The intermediate is the tyre that actually does most of the work in a wet F1 race — full wets exist on paper more than they do on track, since the spray they're built to handle is usually the same spray that gets a session red-flagged first. Our Pirelli F1 tyres guide covers the dry compounds and colour system this tyre sits alongside, and the same crossover-point guesswork that decides an inters call is exactly the kind of gamble that can turn a Virtual Safety Car period, covered in our VSC explainer, into a free strategy swing.