The days of using a standard tire size on RC cars is long gone. Today racers and car enthusiasts can choose a number of different sizes and styles depending on their needs. Since you can pick a variety of sizes, you need to determine what you need and what fits your style of car or truck.
Write down the hub size of your RC car or truck. You'll need to pick a tire that has the right hub size on it or it won't fit on your vehicle.
Pick larger tires with bigger sidewalls if you need control on jumps and doing tricks. The larger tires provide more traction for these moves.
Choose tires with smaller sidewalls if you're a racer who needs something to limit rolling on the track. These tires have more stability than the larger ones.
Look for tires that match the rims in terms of size to increase their lifetime. A 2 inch tire should be mounted on a 2 inch rim, which helps the tire keep its shape with constant use.
Use the right size tires for the track, if you plan on racing. Check with the sanctioning body to determine if they only allow specific sizes.
Stick with tires that were built for your type of car. While you can pick different sizes, the tires should be made for the type such as off road, nitro or truck.