| Offset | Name | Type | Length |
|---|---|---|---|
| 0x0000 | Format Version | U8 | 1 |
| 0x0001 | Locked Tune | U8 | 1 |
| 0x0002 | Car Ordinal ID | U16 | 2 |
| 0x0004 | Unknown Header Data? | U16 | 2 |
| 0x0006 | Unknown Header Data? | U16 | 2 |
| 0x0008 | Unknown Header Data? | U16 | 2 |
| 0x000A | Unknown Header Data? | U16 | 2 |
| 0x000C | Unknown Header Data? | U16 | 2 |
| 0x000E | Engine | U32 | 4 |
| 0x0012 | Drivetrain | U32 | 4 |
| 0x0016 | Car Body | U32 | 4 |
| 0x001A | Motor | U32 | 4 |
| 0x001E | Brakes | U32 | 4 |
| 0x0022 | Spring and Dampers | U32 | 4 |
| 0x0026 | Front Anti-Roll Bars | U32 | 4 |
| 0x002A | Rear Anti-Roll Bars | U32 | 4 |
| 0x002E | Tire Compound | U32 | 4 |
| 0x0032 | Rear Wing | U32 | 4 |
| 0x0036 | Front Rim Size | U32 | 4 |
| 0x003A | Rear Rim Size | U32 | 4 |
| 0x003E | Camshaft | U32 | 4 |
| 0x0042 | Valves | U32 | 4 |
| 0x0046 | Displacement | U32 | 4 |
| 0x004A | Pistons/Compression | U32 | 4 |
| 0x004E | Fuel System | U32 | 4 |
| 0x0052 | Ignition | U32 | 4 |
| 0x0056 | Exhaust | U32 | 4 |
| 0x005A | Intake | U32 | 4 |
| 0x005E | Flywheel | U32 | 4 |
| 0x0062 | Manifold | U32 | 4 |
| 0x0066 | Restrictor Plate | U32 | 4 |
| 0x006A | Oil Cooling | U32 | 4 |
| 0x006E | Single Turbo | U32 | 4 |
| 0x0072 | Twin Turbo | U32 | 4 |
| 0x0076 | Quad Turbo | U32 | 4 |
| 0x007A | Positive Displacement Supercharger | U32 | 4 |
| 0x007E | Centrifugal Supercharger | U32 | 4 |
| 0x0082 | Intercooler | U32 | 4 |
| 0x0086 | Clutch | U32 | 4 |
| 0x008A | Transmission | U32 | 4 |
| 0x008E | Driveline | U32 | 4 |
| 0x0092 | Differential | U32 | 4 |
| 0x0096 | Front Bumper | U32 | 4 |
| 0x009A | Rear Bumper | U32 | 4 |
| 0x009E | Hood | U32 | 4 |
| 0x00A2 | Side Skirts | U32 | 4 |
| 0x00A6 | Front Tire Width | U32 | 4 |
| 0x00AA | Rear Tire Width | U32 | 4 |
| 0x00AE | Weight Reduction | U32 | 4 |
| 0x00B2 | Chassis Reinforcement/Roll Cage | U32 | 4 |
| 0x00B6 | Motor Parts | U32 | 4 |
| 0x00BA | Rim Style | U32 | 4 |
| 0x00BE | Aspiration | U32 | 4 |
| 0x00C2 | Front Track Width | U32 | 4 |
| 0x00C6 | Rear Track Width | U32 | 4 |
| 0x00CA | Front Tire Profile Size | U32 | 4 |
| 0x00CE | Rear Tire Profile Size | U32 | 4 |
| 0x00D2 | Rear Rim Style | U32 | 4 |
| 0x019E | Front Downforce | F32 | 4 |
| 0x01A2 | Rear Downforce | F32 | 4 |
| 0x01A6 | Final Drive | F32 | 4 |
| 0x01AA | Brake Pressure | F32 | 4 |
| 0x01AE | Brake Balance | F32 | 4 |
| 0x01B2 | Handbrake Pressure | F32 | 4 |
| 0x01B6 | Center Differential | F32 | 4 |
| 0x01BA | Unknown | F32 | 4 |
| 0x01BE | Unknown | F32 | 4 |
| 0x01C2 | TCS Slip Definition | F32 | 4 |
| 0x01C6 | Unknown | F32 | 4 |
| 0x01CA | Unknown | F32 | 4 |
| 0x01CE | Front Tire Pressure | F32 | 4 |
| 0x01D2 | Front Camber | F32 | 4 |
| 0x01D6 | Front Toe | F32 | 4 |
| 0x01DA | Front Caster | F32 | 4 |
| 0x01DE | Front Spring Rate | F32 | 4 |
| 0x01E2 | Front Anti Roll Bar | F32 | 4 |
| 0x01E6 | Front Ride Height | F32 | 4 |
| 0x01EA | Front Bump Stiffness | F32 | 4 |
| 0x01EE | Front Rebound Stiffness | F32 | 4 |
| 0x01F2 | Front Differential Acceleration | F32 | 4 |
| 0x01F6 | Front Differential Deceleration | F32 | 4 |
| 0x01FA | Rear Tire Pressure | F32 | 4 |
| 0x01FE | Rear Camber | F32 | 4 |
| 0x0202 | Rear Toe | F32 | 4 |
| 0x0206 | Rear Caster* | F32 | 4 |
| 0x020A | Rear Spring Rate | F32 | 4 |
| 0x020E | Rear Anti-roll Bar | F32 | 4 |
| 0x0212 | Rear Ride Height | F32 | 4 |
| 0x0216 | Rear Bump Stiffness | F32 | 4 |
| 0x021A | Rear Rebound Stiffness | F32 | 4 |
| 0x021E | Rear Differential Acceleration | F32 | 4 |
| 0x0222 | Rear Differential Deceleration | F32 | 4 |
| 0x0226 | Unknown | F32 | 4 |
| 0x022A | Unknown | F32 | 4 |
| 0x022E | Gear Ratio 1st | F32 | 4 |
| 0x0232 | Gear Ratio 2nd | F32 | 4 |
| 0x0236 | Gear Ratio 3rd | F32 | 4 |
| 0x023A | Gear Ratio 4th | F32 | 4 |
| 0x023E | Gear Ratio 5th | F32 | 4 |
| 0x0242 | Gear Ratio 6th | F32 | 4 |
| 0x0246 | Gear Ratio 7th | F32 | 4 |
| 0x024A | Gear Ratio 8th | F32 | 4 |
| 0x024E | Gear Ratio 9th | F32 | 4 |
| 0x0252 | Gear Ratio 10th | F32 | 4 |
Data files are always 598 Bytes.
0x000E - 0x00D2 are installed parts.
0x019E - 0x0252 are tune values, contains some static values.
0x0001 is likely just to tell the game if a tune is locked or not, as in is this tune yours or one you downloaded.
0x01B2 Static value, fixed at 1.0 with a 0-5.5 Range
0x01C2 Static value, mirrors the car's internal Traction Control slip threshold (Range 0.1-30)
0x00D6 - 0x019D are always 0xFFFFFFFF
0x0004, 0x0006, 0x0008, 0x000A, 0x000C, 0x01B2, 0x01BA 0x01BE, 0x01C6, 0x01CA, 0x0226 & 0x022A seem to have fixed values.
0x0206 Rear Caster, can't be adjusted in the game.
You can find my experimental tune viewer at https://martinrefseth.com/forza/tuneviewer/