// race theory

Know the craft.

The vocabulary of fast laps — with diagrams. Tap any card for an AI deep-dive with a worked example.

Technique
Trail Braking
100% braketrail offthrottle

Gradually releasing the brake while turning in, rather than fully releasing before turn-in. This keeps weight on the front tyres for grip and helps rotate the car.

Technique
Threshold Braking
lockup thresholdbrake force

Braking right at the edge of tyre adhesion (just before lockup or ABS engagement) for maximum deceleration in a straight line.

Theory
Weight Transfer
brake: load to FRONT

Load shifting between front/rear (under braking/acceleration) and left/right (under cornering). Understanding it is the foundation of car control.

Theory
Racing Line
late apex

The optimal path through a corner: out-in-out. Late apex on slow corners maximises corner exit; geometric apex on fast corners maximises mid-corner speed.

Balance
Understeer
car runs wide → understeer

Front tyres lose grip before rear; the car pushes wide. Often caused by too-soft front, too-stiff rear, excessive front toe-in, low front tyre pressure, or simply too much speed for the corner.

Balance
Oversteer
rear steps out → oversteer

Rear tyres lose grip first; the rear steps out. Often caused by stiff rear ARB, aggressive throttle, off-throttle lift, low rear tyre pressure, or too-high differential preload.

Theory
Slip Angle
slip angletravelpointing

Angular difference between where the tyre points and where it actually travels. Peak grip occurs at an optimal slip angle (typically 5-8 degrees for racing slicks).

Theory
Apex
geometriclate apex

The innermost point of your path through a corner. Geometric apex = midpoint of the curve; late apex = past midpoint, used to maximise exit speed onto a following straight.

Setup
Brake Bias
FRONT 60%REAR 40%

Distribution of braking force front-to-rear. More forward bias = stable entry but lazy rotation; more rearward = sharp rotation but risk of locking the rear and spinning.

Setup
Differential Preload
left wheelright wheelpreload locks them

How locked the diff is at low torque. Higher preload = more lock under coast/cruise, more stability but reduced rotation. Affects how the car behaves off-throttle.

Setup
Anti-Roll Bar (ARB)
ARB connects L↔R

Connects left and right suspension. Stiffer front ARB → more understeer; stiffer rear ARB → more oversteer. Use them to balance mid-corner behaviour.

Setup
Aero Balance
F downforceR downforce

Front-to-rear downforce ratio. Front-biased aero = sharp high-speed entry but unstable rear; rear-biased = stable but the car pushes through fast corners.

Setup
Tyre Pressure
good patchover-pressured

ACC target hot pressures: GT3 ~27.5–27.9 psi, GT4 ~26.0–26.5 psi. Too high = smaller contact patch and greasy feel; too low = overheating, vague turn-in, and tyre damage.

Setup
Ride Height
front lowrear high (rake)

Distance between the car floor and the ground. Lower = more downforce + lower centre of gravity, but risk of bottoming out. Generally the rear sits higher than the front to create rake.

Setup
Bump & Rebound
diagram pending

Damper settings. Bump (compression) controls how the damper resists being compressed; rebound controls how it returns. Slow bump/rebound affects body movement; fast bump/rebound affects sharp impacts (curbs, bumps).

Setup
Bump Stops
diagram pending

Rubber stops that limit damper travel. Bump stop range = how much travel before they engage; rate = how stiff they are. Critical for high-downforce cars — they prevent the splitter from grounding out at high speed.

Setup
Caster
diagram pending

The angle of the steering axis when viewed from the side. More caster = more self-centring + more dynamic negative camber when turning, but heavier steering. ACC GT3 range typically 10-14 degrees; most cars run 12.

Setup
Toe
diagram pending

How the wheels point relative to straight ahead. Toe-in (front) = stable but lazy turn-in; toe-out (front) = sharp turn-in but unstable. Rear is almost always run with slight toe-in for stability.

v1.0 · APEX/ENGINEERtelemetry live