These are the officially regulated tyres for fia pre 66 touring cars raced in europe under the fia appendix k regulations.
So the cars that race at goodwood, spa 6 hours the masters series currently.
Appendix K exists to regulate all pre 66 cars, GT, Sports and touring with guidelines on what changes and modifucations can be made. Most of the papers are based on the original documents of the period.
A large number of these regulations often state parts must use same fitment positions, same materials and sikilar structure points, hence back in the day a lot of people custom built there own parts to improvebthe cars.
Engines often had limited boring and displacment changes. However they had to be the same original block. Gearboxes could have different ratios homologated if made by the manufacture however final drives and diffs could be interchanged for again sizes manuafctured by the factory or custom built units to the same patterns
Bodywork could have slight changes (now on a car to get a htp you ha e to provide proof that body modification was used on a car raced in period in an international event, a good example the tvr griffiths with the widebody)
A car here in europe has to get a passport or htp to be able to race in fia sanctioned historic events.
A lot of these cars have had a lot of development and as modern engjneering has allowed better tolerances and nore efficient design they are far faster than they where in period.
It is difficult to really know what was done in period as regulations where quite lose as nearly every part could be remade and custom built to better than the factory car and scrutineering was not as strict as it is now.
As forza we dont really have as much control over individual parts i have made the builds hit realistic performance numbers for the cars based on real fia cars performance.
I have looked at dyno sheets for correct cars to find out hp and torque fugures.
The weights are as close as possible to the homolgated minimum weights for the cars
I have tried to avoid carbon fibre driveshafts and upgrading brakes to discs, street isnt really clear what it does, sport definitely mentions disc upgrade so we have steered clear of that.
Most cars in period did fit beefy stronger anti roll bars hence the upgrades we have made tonours, the rquirement in period was that it had to be patterned by the manufacture and produced on a set number of vehicles, often works back door rally/race cars, check bmc competitions department catolog for all sorts of goodies for a mini, mg or healey.
