On a vehicle with Independent Rear Suspension or IRS,
undertaking a front-wheel-only alignment is considered to be an
inadequate procedure. The thrust angle refers to all four wheels
and their relationship to each other in addition to their
relationship to an imaginary centerline that runs from each pair
of wheels down the center of the vehicle. The term "thrust line"
refers to the direction in which the rear wheels are pointing.
The thrust angle can be adjusted on vehicles with adjustable
rear suspensions. On vehicles that do not have adjustable rear
suspensions, the thrust angle can be compensated for by aligning
the front wheels to the rear wheels. Referencing the front
steering geometry to the rear is very important. A
Quadralignment procedure involves aligning all four wheels in
relation to each other. The thrust line may be in the same
position as the vehicle's geometric “centerline”, however there
are variations to this. Ideally the thrust line and the
vehicle’s geometric centerline should line up clos