When replacing solid tires on trailers, if there are no operating instructions for mixed-use tires in the manual, the tire replacement should follow the following principles:

1. It is forbidden to mix different sizes of tires, all tires should be the same size;

2. There is no need to mix radial and bias tires, all tires should be radial or bias tires;

3. It is not necessary to mix tires with different tread patterns, such as mixing full real-time road conditions and summer tires;

4. Never choose a tire with a size different from that of the original tire. The replacement trailer solid tire should have the same size.