By DW Staff | Updated: July 2019
Between hardness and size, there are a lot of numbers flying around that help define how a wheel will perform, and that's before hub variations even enter the mix. This guide will help explain those subtle differences and enable you to find the right wheel for your skating style and surface type.
A wheel's hardness refers to the urethane tire that is actually making contact with the playing surface. This is often represented on a durometer scale ranging from 78A up to 100A, with the lower end of the scale representing the softer wheels. Occasionally, manufacturers will forgo a durometer rating in favor of their own metric such as "Hybrid" or "Firm."
The most common question we get is, "Which wheels should I get for _________?" (insert surface type here). The thing is, even on the same surface, different wheels of the same durometer will perform differently due to variables in the urethane formula and skater weight. So we've generalized all of the world's playing surfaces into four broad categories to help get you started:
Weight also plays a small but important role in choosing the ideal wheel hardness for any given surface. Heavier skaters will naturally achieve more grip (thanks to gravity) and should seek slightly harder wheels than their lighter counterparts. On the flip side, the featherweights of the derby world might want to seek out slightly softer wheels that will help provide the grip that their weight does not. The chart on the left is a good place to start but remember that nothing beats lacing 'em up and trying it out for yourself.
For more information watch: Wheels 101: Durometer
All derby wheels have two important size measurements attached to them, height and width, measured in millimeters. Most wheel specifications will list size as "height x width," so when you see "62x38mm," the wheel is 62mm tall and 38mm wide. These two numbers will each have their own significant impact on the wheel's performance.
Shorter wheels, those with a smaller diameter, are able to accelerate faster than taller wheels. The benefit of taller wheels is that it takes less effort to maintain those speeds. Most indoor wheels are either 59mm or 62mm, while many outdoor wheels are even taller for easy cruising in the great outdoors.
How wide a wheel is will determine how much the wheel favors either balance or agility. Narrower wheels, those around 38mm and slimmer, enhance maneuverability and help prevent clipping wheels with other skaters. A wide wheel will traditionally measure between 40mm and 44mm. Due to a larger amount of contact with the ground, these are more stable.
Now that you have a rough idea of what durometer you want as well as the ideal wheel size for you and your skating ability, you could pick out a wheel with confidence that will serve you well. However, there is much more to any wheel than just the black and white measurements, such as the hub. The hub is the plastic or alloy component in the middle of the wheel that houses the bearings.
One of the most under-appreciated traits of any derby wheel is the shape and depth of its edges. This is because nearly every skating action you make will engage those edges, so how they respond will have a great impact on how the wheel performs.
Wheels that have their urethane tire overhanging the hub will have what we call "soft" edges that flex and provide better traction during lateral movements.
Other wheels, usually the narrower sizes, will have their tires reinforced entirely by the hub. These "hard" edges provide better roll and will typically slide easier.