Buick 1998 Century Owner's Manual page 247

Removing the Spare Tire and Tools
The equipment you'll need
is in the trunk.
(See "Compact Spare Tire" later in this section for more
information about the compact spare.)
1. Pull the carpeted mat up from the floor of the trunk
and turn the center nut on the compact spare cover to
the left to remove it. Then lift and remove the cover.
2. Remove the spare tire.
5-27