I wanted to start racing with no aids (as it seems everyone online thinks that's the way all races should be), and wanted to know how much harder the game is with no abs.
If you fine tune the brake balance / brake strength in the settings, its not much harder if at all. I prefer less braking on the rear to help stabilise it.
Its way easier than GT5. In GT5 the brakes were more sensitive and would lock up at a moments notice. Now in GT6, I can just get in any car with its default 5/5 brake settings and produce a fast lap without messing up.
If you genuinely want to learn, you'll get the hang of it. When I actually tried to learn it it wasn't as hard as I thought it would be. It adds a whole new dimension To the game.
