A modern race weekend is structured around the moment cars enter restricted conditions. After that point setup cannot be altered, which means the race is largely decided before qualifying begins.
What the restriction covers
From the start of qualifying until the race, teams may not change the elements that define how a car behaves, including aerodynamic settings, suspension geometry and ride height.
Permitted work is limited to a defined list, covering safety checks, fluid changes and adjustments that do not alter performance characteristics.
Breaking the restriction is allowed but carries a penalty, usually a pit lane start, which teams occasionally accept when a car is fundamentally wrong.
Why the rule exists
Without it, teams would run a low-drag configuration in qualifying and a different one in the race, so grid positions would describe a car that never raced.
It also constrains cost. Unlimited overnight rebuilds favour the largest teams, since the work requires personnel and spare components at every event.
Restricted conditions additionally shorten the working day, which was a factor in their introduction after concerns about hours worked at circuits.
The compromise every team makes
Qualifying rewards a low-drag, low-downforce configuration, while race pace rewards tyre management and stability, which usually points the other way.
Teams therefore choose a setup somewhere between the two, weighted by how difficult overtaking is at the circuit.
At a track where passing is hard, teams bias towards qualifying. Where passing is easy, they accept a worse grid slot for stronger race pace.
How practice sessions are used
Because setup freezes, practice becomes the entire development window. Sessions are divided between single-lap runs and long runs on race fuel.
Long runs matter more than headline times, since they reveal tyre degradation, which is the variable that determines strategy.
Weather during practice therefore has outsized consequences. A wet session removes the data on which the whole weekend's decisions depend.
What happens when conditions change
If the race is wet and the car was configured for dry running, the team must race what it has. Only limited changes are permitted even then.
Regulations allow certain adjustments when a race is declared wet, which is why teams monitor forecasts closely before the restriction takes effect.
Forecasting therefore becomes a competitive discipline, and a team reading the weather correctly can gain more than a chassis upgrade would deliver.
