Skateboard wheels are available in a variety of colors, sizes and degrees of hardness. Skateboards have two stats, there is the diameter of the wheel which means how tall the wheel is and durometer which means how hard the wheel is.
When making the choice of what kind of wheels to get, most skaters are happy with wheels from 52mm to 54mm diameter, with a hardness of 99a. But, if you want to give it a little more thought, then make sure you ask yourself what kind of skateboarding you will be doing. There is a few varieties of skateboarding and the type of wheel that you have on your skateboard really depends upon the type of skateboarding you are looking to do.
Transition / Vert Skateboarding
Larger skateboard wheels roll a lot faster, and if you are riding ramps then this is what you want. You will want a wheel that is between 55-65mm size Even though many ramp skateboarders will use even larger wheels if you are just learning you will want to try something like a 60mm wheel first, with a hardness of 95-100a.
Street / Technical Skateboarding
Skateboarders who like doing flip tricks often like smaller wheels, this is because the smaller wheels are lighter and closer to the ground. This makes some skateboarding tricks easier and faster. When doing this type of skateboarding, you will want to try between a 50-55mm skateboard wheel, with a hardness of 97-101a.
Both / All Terrain Skateboarding
If you are doing this type of skateboarding you will want a wheel that is somewhere in the middle of the wheel scale, with slightly softer skateboard wheels. You will want to try a wheel size of 52-60mm, with 95-100a hardness. This will give you a balance between speed and weight.
Cruising wheels are much larger for speed the wheel size is usually between 64-75mm and much softer. This is for riding over rough terrain the wheel hardness should be between 78-85a. There is other wheels available for the cruising style of skateboarding, these types of wheels are huge dirt wheels with knobs, this type of wheels are not recommended for skateboards. They are more recommended for long boards or dirt boards.