I too have had trouble staying on the track in an Indycar using the
default setups at both Talledega and especially Bristol. At talledega, I
have severe quick oversteer mid-turn at high speed only, and the bristol
setup gives bad oversteer at all parts of the turn. My fix has been to
reduce front and increase rear downforce by all means available,
including tire pressure, shocks, wing, and even reverse stagger. Works
pretty good at Bristol, but not too successful yet at Talledega. Let me
know if you do any good.