604c6ab6_a_guide_to_the_trickier_menus___Problem
[Solutions] Tire pressure is too low in one or more tires. Too little positive front caster. Too much front toe-in or any toe-out in rear. [Problem] 
Straightline instability
The Ticket Bastard: Tuning in Forza 3: a guide to the trickier menus.
Problem