The player's Titanium Body Digi-Beetle is given a different model based on its TIRES part, or lack of such.

502TNKB - Chain TIRES
505TNKE - no TIRES installed
508TNKH - Ring TIRES
512TNKL - Plate TIRES
515TNKO - Aero TIRES
518TNKR - Gravi TIRES

Gravi TIRES cannot be installed in a Digi-Beetle that has a Titanium Body, which leaves that model unused in regular gameplay.