Mazda RX-8 Workshop Manual page 3758

3. Remove the bolt, then remove the bracket.
4. Remove the bolts, then remove the rear door lock striker (upper).
5. Install in the reverse order of removal.
6. Adjust the door. (See DOOR ADJUSTMENT.)
Lower
1. Remove the outer scuff plate. (See OUTER SCUFF PLATE REMOVAL/INSTALLATION.)
2. Remove the screws, then remove the rear door lock striker (lower).