Custom Tracks are user made tracks which play on a different track that is different from the default tracks in the original game. You can access them via Riivolution or a back-up disc. Most of these tracks are available on the SFP server which need to patch the original .SZS file that it needs to be patched over. There is a downloadable version of these custom tracks which MrBean35000VR has created a track list for his CTGP (Custom Track Grand Prix). However, downloading this will void your warranty, which means you can't ship your Wii to Nintendo when it is experiencing problems unless it's Error Code 20102.