Most trucks that are moving on our roads are semi-trailer trucks, they can carry heavy loads and can be loaded by containers from ships and then be driven across the continent for deliveries. With the containerization a lot of pressure has been put on quick deliveries by land with semi-trailer trucks. To distribute the high weight they tend to have 2 axels on the trailer and 3 on the tractor unit that pulls it. The steering axel has single wheels and the 2 drive axels of the tractor unit tend to have dual wheels and the same goes with the 2 axels on the trailer.
So when it comes to the amount of tires on a semi-trailer truck you tend to have 18 wheels with tires. You will have different tires for the steering axel position and for the drive axel position versus the trailer tires. There are some differences in the properties needed so make sure that you select the correct tire for the intended position. You will have 2 steer tires, 8 drive tires and 8 trailer tires on an 18-wheeler semi-trailer truck. So getting a full set of truck tires can get quite costly, but you don’t want to skimp on quality as that can impact your safety. Retreading tyre can be an option, if they are of good quality and the tire carcass is in good shape.
Buses have similar situation, there are a lot of tires, often with dual wheels in the back and can have one or two axels, so the bus will have either 2 axels or 3 axels. Bus tires don’t have the different tires for the different positions the same way that trucks have and they usually have bus as part of the tire name. They do though differentiate if it is city bus or a long haul bus, where city buses are more durable for pavement impacts on the sidewall and the long haul are more durable for long haul driving, where haul tires are the right choice.
For both buses and trucks there will is a need to have proper winter tires if you plan to drive in areas where there will be winter conditions. You should have 3PMSF symbol on the sidewall if they are approved for winter conditions. Some countries demand that you have this if you will drive through them, others should but they might no have that yet.