Another suggestion that can help a lot new players: when a new version of a mod bike has physics changes, sometimes the old setup files cause a crash when loaded.
Also, even being aware that you must delete all setup files for a given bike, this is a bit of a pain because of the way the setup files are organised (folder structure is per track, per bike): it gets extremely annoying when you have an entire bike set (multiple bikes) and 100+ tracks.
Ideal solution: put some sort of versioning in the bikes and their setup files (old setup on new bike --> avoid loading and show pop up warning).
Half-baked solution: change the setup files folder structure to "bike/track" (instead of "track/bike").