Setup Lab

Balance and corner load

Read axle, left-right, and diagonal scale loads as a system so weight placement does not hide crossbind or steering problems.

Four readings beat oneLevel the scalesRepeat race posture

ILLUSTRATED LOAD MAP

Four pads expose sums a total scale hides.

Four-scale contact-load map A top view shows scale pads LF, RF, LR, and RR, crossing diagonal sums, and front and rear totals. Drawing standard: endpoint-defined lines, fixed reference points, declared view, and a scale-independent measurement grid.

W = LF + RF + LR + RR
ΔX = (LF + RR) − (RF + LR)
cross percentage = 100(LF + RR) / W

Illustrative load map, not a target

48.5, 49.0, 51.0, and 51.5 lb produce W = 200.0 lb, front = 97.5 lb, rear = 102.5 lb, equal 100.0 lb diagonals, and 50.0% cross.

A nonzero ΔX is a diagnostic, not proof of crossbind. Driver asymmetry, ballast, pad calibration, wheel diameter, support height, floor slope, steering, or axle geometry can create it. Static redistribution alone also need not increase total rolling resistance.

VALIDATE THE SCALE PLANE

Rotate the question before adjusting the car.

Zero all pads and check each with the same known load.
Put support heights into one verified plane.
Capture at least three roll-off-and-resettle trials.
Swap pad positions or rotate the car when practical; see whether the effect follows the pad or floor.
Change nothing until the effect exceeds ordinary process spread.

Pad mismatchOne pad has an offset.

Side contactShell, brake, cable, or helper carries load.

Posture driftHead, hips, hands, or feet move.

Premature diagnosisA load clue is called crossbind without a plane check.

Return to the Setup Lab learning path and calculators

GARAGE WORKSHEET

The minimum record needed to act on this guide.

QUESTION THIS STATION ANSWERS

Does an apparent corner or diagonal load difference follow the pad, the floor, the driver, a wheel position, or the car?

BRING

Four matched scales with equal-height rigid platforms
Long level or verified plane reference plus one known check load
Wheel-position map, driver-position photo, and four-corner log

LOCK BEFORE READING

Exact wheel IDs and clocking, steering neutral, cable and clamp state
Fully dressed driver pose and a no-contact perimeter check
One roll-off, settle, and read sequence

WRITE THE RAW RECORD

LF, RF, LR, RR, front, rear, left, right, both diagonal sums, and total
At least three settles, then one controlled pad swap or car rotation when safe
Whether the effect follows pad, floor location, driver state, wheel position, or car

DECISION GATE

A difference that follows a pad or floor location is not a car adjustment signal. A difference that stays with the car after full resets is a diagnostic; confirm geometry independently before calling it crossbind.

VERIFY NEXT

Resolve fixture faults first, check cross-plane geometry, then repeat the final load map after all clamp work.

Authority check: reviewed July 27, 2026. Reopen the linked official rule book, current division plan, amendments, and inspection guidance on the day of work. A measurement method never grants permission to alter a controlled part.

Save the test in My Race Shop Return to the full Setup Lab workflow

THE LOAD MAP

Total weight is only the first number.

Four-pad scales show how the car shares its total load among left-front, right-front, left-rear, and right-rear contact patches. Summing the front pair and rear pair gives axle load. Summing left and right gives side bias. Comparing diagonal pairs provides a diagnostic clue, not proof of crossbind or its cause.

total = LF + RF + LR + RR
front = LF + RF | rear = LR + RR
diagonal A = LF + RR | diagonal B = RF + LR

MEASURE WELL

Bad scale setup creates fake chassis problems.

Place all pads on a rigid, level plane and zero them together.
Install the exact race wheels or approved load simulators consistently.
Set tire or wheel orientation, steering neutral, cable tension, and final fastener state before reading.
Put the fully dressed driver in the repeatable race position without touching walls or helpers.
Roll or settle the car using the same procedure, then capture all four numbers without pushing on the shell.
Repeat. If readings do not repeat, fix the measurement process before adjusting the car.

INTERPRETATION

Do not chase perfectly equal corners blindly.

Equal quarter loads are not an automatic speed target. Driver placement, axle geometry, legal weight mounting, and class design may produce different front and rear loads. The goal is a legal, stable, low-loss configuration with minimal unintended diagonal load and predictable steering.

Wheel swaps make balance especially important. A setup that only works because its quickest wheels sit on its heaviest corners can unravel as soon as wheels move between cars. A neutral chassis is more robust to swapped wheel variation.

If a diagonal difference changes when you rotate the car or swap scale pads, suspect the floor or scales. If it stays with the car, investigate crossbind, axle mounting, weight placement, and driver posture.

SOURCES & FURTHER READING

Check the primary material.

Zero Error forum archive: Crossbind Historical 2005 team discussion. Useful shop theory, not a current rule or official instruction.
Zero Error forum archive: Progressive wheel swap Historical explanation of why lane and wheel swaps reduce wheel and lane advantage.
ISBD Rule Book - linked for the 2026 World Championship Official PDF currently linked from Race Week resources; the file itself says revised June 2025.
OpenStax University Physics: Conditions for static equilibrium University-level reference for force and moment balance used in axle-load and center-of-gravity calculations.
NIST Engineering Statistics Handbook: Uncertainties of calibrated values NIST guidance on uncertainty in future results corrected by a calibration curve, including calibration-curve and future-measurement contributions. It does not characterize the whole Derby measurement process by itself.