Do wheels have to be realigned when struts are replaced?
Most of the time, but not always. It depends on the application. When a McPherson strut is replaced on a vehicle where the strut is an integral part of the suspension and it has provisions for camber and/or caster adjustments, the original wheel alignment settings are lost when the strut is removed.
Even if the position of camber bolts and/or upper camber/caster plate is carefully marked prior to removal, variations in manufacturing tolerances between the original strut and its replacement will probably alter suspension geometry enough to require realigning the wheels.
On vehicles with "wishbone" strut suspensions, the strut doesn’t play a role in wheel alignment. On these vehicles, realignment of the wheels after replacing the strut is not necessary.
On vehicles with rebuildable struts, it is not necessary to realign the wheels if only the strut cartridge is being changed. It is necessary to mark the original positions of the upper strut plate and/or lower camber prior to unbolting anything to preserve the original alignment settings.