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Skidpad Calculator

2026-09-27 6 min

Sustained lateral G from skidpad diameter and lap time.

Sustained Lateral G
1.09 g
Lap Speed
49.4 mph

Calculator

Skidpad Diameter(ft) Help
ft

Circle diameter (300-ft standard)

Lap Time(s) Help
s

Steady-state lap

Results update live as you type

Live statistics

Sustained Lateral G

1.09 g

Lap Speed

49.4 mph

Results

Optimal

Sustained Lateral G

1.09g

Lap Speed

49.4mph

Planning estimate from standard automotive formulas. Validate with dyno, timeslip or datalog data when precision matters.

Visualizations

Results overview

1.1Sustained Lateral G
49.4Lap Speed

Sustained Lateral G vs. Skidpad Diameter

Sustained Lateral G

1.1g
02

Formula

Steady-state circle: lap speed over radius gives sustained (not transient) grip.

v = pi x D / t; G = v^2 / (32.2 x R)

Alternative Form

300-ft diameter is the magazine standard

Variables

SymbolNameUnitDescription
DDiameterftSkidpad circle

Explanation

Skidpad isolates sustained lateral grip — no braking, no transitions, just the tires and balance.

Step-by-Step Calculation

Follow each step to understand how the result is calculated from your inputs.

Step 1

Record the inputs.

Skidpad Diameter:300 ft
Lap Time:13 s
Result: 2 inputs ready
Step 2

Apply the formula.

v = pi x D / t; G = v^2 / (32.2 x R)
Result: Primary result = 1.09 g
Step 3

Read every derived output.

Sustained Lateral G:1.09 g
Lap Speed:49.4 mph
Result: Sustained Lateral G = 1.09 g
Final Answer
1.09

Worked Examples

See how the calculator works with different scenarios.

Scenario

Magazine-style grip test.

Inputs

Diameter:300 ft
Time:13 s

Calculation

v = 72.5 fps (49 mph); G = 1.09

Result

1.09 g sustained.

Interpretation

Strong summer-tire grip; R-compounds push 1.2+.

Understanding Your Result

Your Result: Sustained Lateral G: 1.09 g

Typical range: All-season 0.75-0.85; summer 0.90-1.05; R-comp 1.1-1.3; slicks 1.3+.

What This Means

Steady-state cornering grip, magazine-standard.

Why It Matters

The comparable grip figure across cars, tires and setups.

Professional Interpretation

Treat the primary result as a planning estimate, then validate on a dyno, at the track, or with logged sensor data. If measured numbers disagree by more than ~10%, re-check inputs (units are the usual culprit) before changing parts.

Recommendations

  • •Double-check units on every input before trusting the result
  • •Compare against the worked example below to sanity-check magnitude
  • •Validate with measured data (dyno, timeslip, datalog) when it matters

Learn — fuel economy, deeply

Skidpad G is sustained cornering truth.

1 · Where the gallon goes (energy path)

Engine heat

60–70% lost

Coolant + exhaust carry most energy away. Hybrids recover some via Atkinson cycle + regen.

Driveline

5–15% lost

Transmission, differential, accessories. CVTs and 8–10 speed autos lose less.

Aero drag

∝ v²

Doubles from 55→78 mph. Roof boxes hurt more than trunks.

Rolling + brakes

10–20%

Tires, weight, stops. Regen braking (hybrid/EV) reclaims city braking energy.

4 · Measure like a pro (the 3-tank protocol)

  1. Fill to first click at the same pump, record the odometer (Tank 0).
  2. Drive normally for 2–3 tanks; always refill to first click at the same pump.
  3. MPG = total miles ÷ total gallons across all tanks — averaging kills pump-click noise.
  4. Cross-check with the trip computer; a persistent >10% gap means the computer needs calibration — or the car needs service.
  5. Log with an OBD-II dongle for per-trip MPG if you want to isolate commute vs. highway behavior.

Practical Tips

  • •Warm tires with 3+ laps first
  • •Average both directions
  • •Water the pad for wet testing

Common Mistakes

Mixing units (inches with mm, psi with kPa)
Convert every input to the unit shown on its field before calculating.
Trusting a single output blindly
Cross-check with the worked example and, when it matters, a dyno or datalog.

Assumptions

This calculator makes the following assumptions to provide estimates:

Steady-state model: Formulas assume stabilized conditions; transients, heat soak and traction limits are excluded.
Standard factors: Empirical constants (BSFC, VE, drivetrain loss) use typical values — your combination may differ.

Limitations

Be aware of these limitations when using this calculator:

Estimate, not measurement: Predictions carry real-world scatter of roughly ±5–15% depending on the model.
No transient effects: Shift time, wheelspin, spool lag and heat soak are not modeled here.

Frequently Asked Questions

Answers to common questions about this calculator.

Skidpad vs real corners?
Skidpad measures sustained grip; real corners add transitions, camber and bumps — both matter.
Why 300 feet?
Magazine convention — big enough for steady state, small enough for any car. Compare same-size only.

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Related Guides

Deepen your understanding with these educational resources.

Glossary

Technical terms used in mortgage calculations explained in plain language.

MPG
Miles per gallon. Distance travelled per gallon of fuel; higher is better. US gallon = 3.785 L.
L/100 km
Litres consumed per 100 kilometres; lower is better. Standard metric efficiency unit.
MPGe
Miles per gallon-equivalent. EV metric: miles travelled on 33.7 kWh (energy of 1 gal of gasoline).
CAFE
Corporate Average Fuel Economy — US fleet-average efficiency standard enforced by NHTSA.
Rolling resistance
Energy lost deforming tires as they roll. Low-pressure or wide tires raise it.
Aerodynamic drag
Air resistance growing with the square of speed — why highway MPG falls fast above 60 mph.
Hypermiling
Driving techniques (coasting, steady speed, anticipation) that maximise real-world MPG.
OBD-II
On-board diagnostics port. Scanners and dongles read live MPG, fuel trim and fault codes.
Skidpad
Constant-radius circle for steady-state lateral-grip measurement.

Authoritative References

Trusted sources and standards referenced by this calculator.

Applicable Standards

EPA Fuel Economy Testing (40 CFR Part 600)CAFE — Corporate Average Fuel Economy Standards (NHTSA)WLTP — Worldwide Harmonised Light Vehicle Test ProcedureSAE J1321 / J1711 — Fuel consumption test proceduresISO 2575 — Road vehicles symbols & efficiency markings

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