Tyre pressures at Castle Combe

The lap, to scale. Track outline © OpenStreetMap contributors (ODbL).

How hard a circuit works each corner of the car shows up as tread temperature, and temperature is what sets pressure. GripCalc carries corner heating figures for Castle Combe as a starting point: how much hotter each tyre runs over the session's base temperature, from the layout's mix of corners and load. They pre-fill the calculator when you pick the circuit, and your own pyrometer readings refine them from the first session.

ESTIMATED — class-based starting values over an 85°C session base, derived from this layout's type (direction, speed profile, load), and shared with circuits of similar character rather than measured here. Not gospel: enter your own pyrometer figures after a session and they take precedence.

Castle Combe, on paper

Lengths are measured from the OpenStreetMap geometry drawn above; the longest straight is derived from the same line and is approximate. Section names are the venue's, and can belong to any of its layouts.

What Castle Combe asks of a tyre

Castle Combe measures 0.92 km on the map, with 14 corners counted along that line. That is a corner every 65 m, so the tread is asked for something almost continuously: heat arrives early and keeps arriving, and pressures climb through a session faster than the morning's ambient reading suggests. It is a short lap, so those corners come round again and again within a session — heat accumulates lap on lap, and going out with pressures that were right at the start is the classic way to finish a session several psi over target. Nothing on the lap is straight for longer than about 189 m, so there is no stretch where the tread gets a real chance to cool.

DERIVED — length, corner count, hands and straight measured from the mapped lap drawn above. Corner counting is a judgement (a double apex can be read as one corner or two), so treat these as this line's reading of the circuit, not a series' official figures.

Castle Combe is an old airfield perimeter: very fast, gently cambered, and famously bumpy in places. Quarry and Tower are proper stops out of sustained speed, and the two chicanes ask the car to change direction hard over kerbs. High average speed keeps tread temperature up; the bumps make stable pressures matter more than usual.

A 992 GT3 on Cup 2 R at Castle Combe

Published hot target 30.5 / 32.0 psi at 92°C tread, on a 15°C morning, with the corner figures above: cold set 21.4 / 21.5 front, 22.5 / 22.6 rear. A different car, tyre or morning moves every number, which is what the calculator is for.

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