F1 drivers sustain more G's forces simply they use the brakes/throttle more, that creates more G forces. Nascar are bumper cars, worlds worst drivers on the planet and CART/Indy cars have bigger engines, larger cars but are not equipted to sustain the acceleration and breaking that F1 cars do. Just my 2 cents... avid F1 fan. I don't watch Indy racing anymore... americans want accidents and aren't interested in true driving/racing thrills. You can't compare F1 - the pinnacle of motorsports with Nascar/Indy cars... they are each different.
Owning a 1977 200zx for 16 years I can finally own a Z now, hence my name: 'IcanZnow', finally I can own a Z... my life is complete.