The size of automobile tire screws is set according to the design and manufacturing standards of vehicle wheels. Generally speaking, the size of automobile tire screws depends on the following factors:

1. Hub aperture: The size of the tire screw needs to match the aperture of the vehicle hub to ensure that the screw can be correctly installed on the hub and tighten the tire.

2. Thread specification: The thread specification of the tire screw needs to match the thread on the hub to ensure that the screw can be screwed into the hub correctly and play a fixed role.

3. Screw length: The length of the tire screw needs to be moderate, which should be able to completely penetrate the tire and wheel hub, but not too long to avoid affecting the installation and driving safety of the tire.

4. Screw material: Tire screws are usually made of high-strength alloy steel to ensure that they are not easily deformed or broken when bearing vehicle load and vibration.

5. Screw head design: The head design of tire screws is usually hexagonal head or special shape, which is convenient for installation and disassembly with torque wrench or special tools.

Generally speaking, the size of automobile tire screw is set according to the design requirements and standards of vehicle hub, so as to ensure that the screw can be correctly installed on the hub and play a role in fixing the tire. When replacing the tire screws, the screws with the correct size and specification should be selected to ensure the safety and stability of the vehicle.