One can get away with fairly hard bumping. If you are side by side, you can force the car beside you (but don't do it on purpose, just follow your line). Then you MUST consider that for the next corner he is still there. Cut into hes line and you're screwed.
What you MUST NOT do is touch another car (or allow them to touch you) with what feels like the back half of the side of your car (from the wheel it feels that way, from the replays you can not tell, especially since most replays end BEFORE the disqualification event occurred). Instant disqualification. Ridiculous. I mean, I got away with bumps that I would have disqualified me for, but was disqualified many times for barely audible brushes with other cars.
If you are an early breaker, do not do it with other cars right behind you, better to choose a different line, that will allow you to either circle them on the outside of the curve or cut in on the inside. When cutting in, mind the corners where the AI uses excessive braking, or you are surely to smack into a car in front of you and be disqualified. Better to go on the outside if you can to avoid that.
