// Free tuning tools
Performance,
dialed in.
Fast, ad-free calculators for people who actually turn the wrenches — then a build planner to spec your car and share it. No sign-up, no fluff, works on your phone in the garage.
Tire Size Calculator
Compare two tire sizes — diameter change, sidewall, circumference & speedometer error.
LiveWheel Offset & Fitment
ET / offset, backspacing and poke — check if a wheel clears.
LiveBolt Pattern (PCD)
mm ↔ inch, stud spacing and common-pattern match with a diagram.
LiveSpring Rate
Wheel rate via motion ratio, ride frequency and N/mm ↔ lb/in.
LiveGear Ratio & Speed
Speed per RPM in every gear, final-drive swaps and rev-drop.
LivePower-to-Weight
hp/ton, kg/hp and where your build really stacks up.
LiveHP ↔ kW Converter
Horsepower, kilowatts and PS — converted cleanly.
Live0–60 & ¼-Mile Estimator
Estimate acceleration from power and weight.
LiveTrap Speed HP
Estimate flywheel horsepower from your ¼-mile trap speed or ET.
LiveBoost & Compression
Effective compression, pressure ratio and density.
LiveFuel Cost & Economy
Cost per trip, L/100km ↔ MPG and running costs.
LiveCompression Ratio
Static CR from bore, stroke, chamber, gasket & deck.
LiveEngine Displacement
cc, litres & cubic inches from bore, stroke & cylinders.
LiveMean Piston Speed
m/s & ft/min from stroke and RPM — the reliability read.
LiveEngine Airflow (CFM)
Intake airflow in CFM, kg/min & g/s from displacement, RPM & VE.
LiveTurbo Size
Required compressor airflow & pressure ratio for your power target.
LiveBrake Bias
Ideal front-to-rear brake split from weight transfer.
LiveCorner Balance
Front/rear, left/right & cross-weight from four corner scales.
LiveAFR ↔ Lambda
Air-fuel ratio ↔ lambda per fuel, with tuning targets.
LiveE85 Mix
Blend two fuels to a target ethanol % — exact volumes.
LiveInjector Size
Required cc/min & lb/hr plus fuel pump LPH from target hp.
LiveDyno Correction
SAE J1349 correction factor from temp, pressure & humidity.
LiveDensity Altitude
Air density, density altitude & NA power loss for the day.
LiveGearbox Designer
Sawtooth speed/RPM chart, top speed per gear & shift rev-drops.
LiveOBD-II Code Lookup
Search 1,100+ generic powertrain codes with symptoms & common causes.
Tune It
Dial in the fuel curve, run the dyno and chase peak power — go too lean and it knocks.
GameReaction Time Test
Drag-strip Christmas tree — stage up, wait for green and launch. Beat your best, don't red-light.
GameDrag Race
Launch your My Build car down the ¼-mile — tree start, manual shifts, chase your best ET.
How to read a tire size
Every number on the sidewall — width, aspect, load index & speed rating.
GuideWheel offset explained
ET, backspacing and poke — and whether a wheel will clear.
GuideCompression ratio explained
What it is, how it's calculated and what a good ratio is.
GuideAFR & lambda explained
Mixture, tuning targets and why lambda beats a bare AFR number.
GuidePower-to-weight explained
The number that really predicts pace, and how to compare fairly.
AllAll guides →
Plain-English explainers for the maths behind the mods.
Start with the tire size calculator
The most-used tool — diameter, gearing and speedo error in one screen.