# Driving or setup: separating causes

João Paulo Santos, Founder. Published 29 September 2026. Last updated 29 September 2026.

## Short answer

Check whether the driver did the same thing in both runs before you credit or blame the setup. If the inputs differ in the corner window, test the driving explanation first; if they match and the car still behaves differently, look at the setup.

## Why the order matters

A setup change and a driving change can cost the same lap time. Traces show both the inputs and the result, so read the inputs first. If they differ, the car was driven differently and the setup change is not yet isolated.

## Signs in the traces

What each pattern suggests, and what would confirm it.

| What you see | Points to | Confirm with |
| --- | --- | --- |
| Earlier lift or earlier braking in one run | Driving | Repeat laps with a fixed braking reference. |
| Later or more gradual return to throttle on exit | Driving, or traction limited by setup | Throttle against steering: did the driver wait for the car? |
| Same inputs, lower minimum speed | Setup or tyre state | Hot pressures and tyre temperatures for both runs. |
| More steering for the same corner speed | Understeer from setup or tyres | Steering angle and yaw rate, if logged. |
| Difference on only some laps | Consistency, traffic or track state | More clean laps before any conclusion. |

## Read one corner window at a time

Pick the section where the time changed and read speed, throttle and brake through that window only. Compare where the lift starts, where the brake peaks, the minimum speed and where full throttle returns. A whole-lap overlay hides these details.

## Put the missing context on the table

Traces rarely carry everything. Write down what changed and what was not measured: setup changes, fuel, tyre age, hot pressures, wind and the driver's own comment.

> **Rule of thumb**
> An explanation that depends on a missing measurement is a hypothesis, not a finding. Name the measurement that would confirm it.

## When it is both

A setup change often changes how the car is driven. More front roll stiffness can push the car on entry, and the driver may lift earlier to manage it. Treat that as a chain to test, not as proof of either cause: hold the setup, repeat a driving cue and see whether the gap closes.

## Worked example from the synthetic session

In the synthetic Jerez session, run B lifts earlier and returns to throttle later through the corner window between 2100 and 2800 m. Run B also moved the front roll bar from 3 to 4, and hot tyre pressures were not measured in either run.

Both explanations fit. The driving explanation has direct evidence in the throttle trace. The setup explanation is plausible but unconfirmed, because the pressures that would support or rule it out are missing. The first test is to hold the setup and repeat the driving cue, as described in [Designing one discriminating test](https://apexscout.racing/guides/one-discriminating-test).