The zip contains two database files you can use in 25% and 50% career mode and gives you back the tyre scaling behaviour of F1 2012 = none.
The 100% race distance of career tracks is reduced in each database to the number of laps of a 25% / 50% race and fuel load of the 100% race is adapted in each database to match the shorter distance. Otherwise you would get the fuel amount for a full 100% race and you could run on rich mix the whole race.
Please bear in mind this works best in career mode. Any other mode wasn't tested and could give you unexpected results. If you want to run longer races you have to switch back to the original database.
You don't have to start a new career. Although, I'm not sure what happens if you are in a race weekend and change the database. Best finish the race weekend and change it afterwards.
Tested for 25% database in Melbourne, Malaysia and China (wet) so far and AI pitted for their one obligatory stop.
Edit: Just changed number 4 description.
- Search for your database.bin file in the database directory of F1 2013 and make a backup.
- Unzip the file and rename the favourite race length database-xx.bin to database.bin
- Copy the new database.bin in F1 2013/Database directory.
- Make sure the race length in F1 2013 career mode and Grand Prix mode is 100%, otherwise it doesn't work. It happend to me that although in career mode I had 100% race length set up it took the wrong setting.