All About Inline Skate Wheels
Inline skating is all the fun of ice skating, skiing, hockey, or whatever the heck you want to make of it -- without the need for a rink, mountains, or snow. My first article on skating covers wheels, which can make a big difference in your skating enjoyment.
Types of Wheels
There are three basic types of wheels you'll likely encounter: speed, hockey, and aggressive (aggro). Most recreational or fitness skates come with speed wheels or variants thereof. Hockey and aggressive skates will of course come with hockey and aggressive wheels, respectively. If you're not sure what kind you have, they're probably speed wheels.
Speed wheels (also recreational or fitness wheels) are generally large in diameter, medium hardness, and have an elliptical profile. Hockey wheels are medium diameter, come in a range of hardness, and have a rounded to almost flat profile. Aggressive wheels have a small diameter, are very hard, and have an almost flat profile.
Before going into further detail on the wheel types, I must be clear on the terms used to describe wheels. Most are very straightforward:
Diameter: Distance across the wheel (from top to bottom), usually measured in millimeters. This is usually the first measurement listed for a wheel. Generally speaking, larger wheels roll faster than smaller ones.
Durometer: Hardness of the wheel. This is usually the second measurement for a wheel, followed by an 'A'. Thus a 76mm/78A wheel is 76 millimeters in diameter with a hardness of 78A. Softer wheels tend to grip better but wear faster, whereas harder wheels have less grip but last longer. And of course a softer wheel will absorb more road shock than a harder one.
Profile: This is a less obvious property but it's very important. If you look at the wheel on end (as above), you can see a dramatic difference in how rounded various wheels are. For fitness skating you want a sharper edge for less rolling resistance, whereas for hockey you want more grip plus better wear for all your turns and stops.
Hub Size: Most skates use 608-size hubs, i.e. the hole in the wheel fits a standard 608 bearing. Some fitness and speed skates are now using 688 "micro bearings," so be careful when buying speed wheels that you get the right hub. You can easily switch bearing sizes on a skate as long as you get matching wheels.
Wheels for Fitness/Speed Skating
If you're skating mostly forward and not doing tricks, you'll want speed wheels. They're designed to go fast and last a reasonably long time. Currently most of these wheels are around 80mm in diameter with 78A to 82A durometer. Some older skates will have 76mm wheels but can take larger. Usually the skates have the maximum wheel diameter printed on the frame, or failing that, check the manual.
I recommend 80mm or larger wheels. They'll roll faster and also provide better shock absorption because there's more wheel between the road and your frames. Durometer is largely a matter of matching your road conditions: if you need extra grip, especially if your conditions are unpredictable (e.g. an urban environment), go softer. Your wheels will wear out faster but the extra safety margin is worth it. If you're on smooth bike paths or residential streets, you can afford to go harder. If you don't know where to start, go with the largest size your frame will accommodate and try 80A durometer.
Wheels for Freestyle/Street/Dance Skating
If you're all about the journey and not so much the destination, then why not have some fun? When I say "freestyle" skating I mean skating with artistic flair: fancy footwork, jumps, spins, and that kind of thing. I love freestyle skating. That's what I got into skating for in the first place.
The best wheels for freestyle are hockey wheels. Even if you have recreational skates, you can still put hockey wheels on them. The problem with using speed wheels is that you'll wear them flat in no time. With footwork and spins the elliptical profile grinds right off because it's not designed for that type of use. Hockey wheels, on the other hand, start with rounded to flat profile, so there's more "meat" there to take the wear.
My suggestion for a balance between speed and footwork is 76mm/78A. That way they won't feel too slow when you're going straight, but they'll still be plenty of fun when you're going anything but straight.
Wheels for Hockey
Hockey requires hockey wheels, right? Right. You'll want to decide if you'll be playing indoors or outdoors, and buy to match. I'm not an expert on inline hockey, so check with your teammates to see what they're skating.
Wheels for Aggressive/Ramp Skating
Aggro skates are a breed unto themselves, and there are a ton of specialty aggro wheels on the market. I don't have experience here myself, so I can't make any recommendations.
If you look at your wheels end-on after you've been skating a bit, you'll notice the wheels usually don't wear evenly. When the uneven wear is clearly visible, you'll want to rotate your wheels.
On four wheel skates I recommend swapping wheel 1 with wheel 3, and wheel 2 with wheel 4. (Thought of another way, everything slides back two slots, with the back ones wrapping around.) On five wheel skates I also slide everything back two slots.
You also want to switch the wheels between the left and right skates, and make sure that the side of the wheel which used to be on the inside is now on the outside. Depending on your stride you may wear the inside edge more than the outside; make sure on a rotate so that the wheel doesn't keep getting more lopsided.
For skates that have hi/low frames (different size wheels for the front two and back two wheels), swap wheels 1 and 2, wheels 3 and 4, plus all wheels swap sides.
When to Replace Your Wheels
Some people will keep skating on wheels until they're down to the raw plastic hubs. Others will replace a speed wheel when it's no longer elliptical. I say replace them when it's clear that you'd benefit from new wheels.
As a case in point, I had ancient 76mm wheels on my speed skates that were very clearly worn. They still had plenty of wheel left to skate on, but I felt they were significantly detracting from my skating experience. I replaced them with new 82mm wheels and wow! the skates rode much better. They were faster and I felt dramatically less road noise through the wheels, even though the durometer was the same as the old wheels.
For freestyle skating (and probably hockey and aggro), wheels wear flat anyway so you can get away with letting them wear longer.
Buying the right wheels will have a very definite impact on your skating happiness. It's worth your while to decide your skating priorities and buy wheels to match. You'll need to decide the best match for you, but hopefully these recommendations have given you a place to start, plus the background to know what to look for.