: Use a tool like WinRAR or 7-Zip to extract the .rar archive.
MX Bikes Official Forum : A great place for troubleshooting and finding technical tools like the Resolute MXB Track Builder .
If you are looking for more mods or updates to existing packs, these community-driven sites are the primary sources:
To use the contents of this file, you generally need to extract it and move the folders to your user directory. How to Install MX Bikes Mods
MXB-Mods.com : The central hub for tracks, gear, and bike skins.