Tyre allocation for a race weekend is decided long before cars arrive at the circuit. The number of sets is limited and cannot be increased, which turns every practice lap into a strategic decision.
Why the allocation is fixed early
Tyres are manufactured and shipped weeks ahead, so the supplier needs the compound selection and quantity settled before production begins. Freight for a global calendar cannot be assembled at short notice.
Selections are therefore made against expected conditions rather than actual ones. A weekend that turns out unusually hot or cold is contested on tyres chosen for a different forecast.
The supplier also nominates which compounds from its range are available at each circuit, based on surface abrasiveness, corner loading and ambient temperature history at that venue.
Practice running costs strategy
Every set used in practice is a set unavailable for qualifying or the race. Running to gather data therefore consumes the resource the data is meant to inform.
Teams plan a running programme that extracts the maximum information from the fewest sets, often splitting different compounds between the two cars to double the coverage.
A team that discovers a problem late faces a difficult choice, because correcting it requires running that will leave the car short of fresh tyres on Sunday.
Compound behaviour drives everything
Softer compounds generate grip quickly and degrade faster, while harder compounds take longer to reach working temperature and last considerably longer once there.
Degradation is not linear. A tyre can hold performance for a period and then fall away sharply once the surface or the underlying structure passes a threshold.
Predicting where that threshold sits at a given circuit and temperature is the central problem of race strategy, and it can only be studied during practice.
Mandatory usage rules
Regulations often require that more than one compound be used during a dry race, which prevents a team simply running the most durable option throughout.
That requirement guarantees at least one pit stop and creates the strategic branching that makes races unpredictable, since teams may split their cars onto different plans.
Rules also frequently return sets to the supplier after each session, which enforces the allocation rather than relying on teams to manage it honestly.
What happens when weather intervenes
Wet weather tyres are supplied separately and do not count against the dry allocation, so rain does not directly cost a team its race sets.
It does cost information. A wet practice session leaves the team without degradation data, forcing strategy to be built on simulation and on data from previous years.
Teams in that position generally adopt conservative plans, because an aggressive strategy without supporting data is a gamble rather than a calculated risk.
