Workshop | All about wheels | All about wheels

Skateboard Wheels are made from the petrochemical called Urethane. It's an awesome material which is bouncy, grippy, and comes in all sorts of cool colours. Back inthe day they used to be made from rubber, UHWMPE plastics (like sliding pucks), clay or even metal - thankfully things have moved on since then?

Wheel Shapes
Cores
Urethane rebound, durometer ratings, grip and speed over different surfaces
Flatspots
Wheelbite
Progressive Grip and why it's good

1. Wheel shapes

The profile of a wheel (as you look at it from the front or back) affects the way a wheel rides way more than most people realise. The three things to consider are Diameter, Contact Patch and Edges.

The diameter or size of a wheel is pretty important. In conventional wisdom larger = faster and smaller = quicker acceleration. This is because smaller wheels have less inertia to overcome to get spinning and larger wheels have a higher road speed for the same rotational speed. This makes larger wheels faster as friction losses from your bearings increase with rotational speed so there is less drag from your bearings etc at any given road speed. There is, however, more to it for us longboarders?

The main difference you will notice between bigger and smaller wheels is that you can roll much faster over rough surfaces when you are on bigger wheels, and a few mm can make all the difference. This has to do with the radius of curvature of the outside of the wheel compared to the obstacles you are trying to roll over (rough surfaces looks like thousands of little rocks to something as small as a skate wheel) The more gentle the curve the larger stuff you can handle. This sort of stuff is not a concern to shortboarders who tend to stick to perfectly smooth skate parks and paved areas etc. Wheels go up to 99mm using regular urethane, but there are issues of wheelbite with low decks and turny trucks.

The contact patch is the width of the wheel that contacts the ground when you're riding. The wider the contact patch the more grip and less progressive the slide, but the less likely you are to get flatspots. Narrow wheels are looser and slidier, but wear down faster and flatspot easier as there is the same weight over a smaller area of wheel - so more pressure on the urethane.

The edges of the wheel affect how it slides sideways across the road and how much grip it has. There are three kinds of edges:

Square edge
A square or sharp edge profile wheel tends to be quite unprogressive and very grippy. They're best for slalom and fast carving, where you need as much grip as you can get. They have so much grip becuase the square "lips" of the wheel and distort over bumps in the road surface.
Bevelled edge
Halfway between radiussed and square edges is a bevelled edge - where the wheel is machined at an angle to the rest of the wheel. It's not as grippy as a square edge, but less progessive than a radiussed edge.
Radiussed edge
A radiussed edge is what you need for sliding and hard carving. As the wheel is shaped with a nice circular edge it travels across the road sideways much better than a square or bevelled wheel, but it also lets go a bit earlier and more progressively. This makes it easy to loose speed by drifting the board sideways or sliding at slower speeds, but not so good if you need loads of grip. A bigger radius will last longer as the wheel gets worn down, and will be less grippy than a smaller radius. (PIC) Some wheels have radiussed edges on the outside only, working on the principle that any large obstacle or dent in the road surface you are likely to hit will be coming from the outside edge of your board.

2. Cores
Most quality wheels out there have a plastic core that the bearings sit in. The core spreads the heat through the wheel and stops the bearings (which get super hot at speed) melting the Urethane. It is VERY BAD when this happens - melting (or "puking") a wheel can be very dangerous! Exposed cores work better for heat dispensation than internal cores.

The core also helps to maintain the cirular integrity of the wheel, which helps to prevent flatspots. A wheel with a big core is more likely to stay spinning when sliding sideways, so it'll stay round for much longer than a coreless wheel. Cored wheels are also faster on smooth surfaces, as there is less urethane to compress and rob you of your speed - but this means that large-cored soft wheels can be quite slow over rougher surfaces.

3. Urethane rebound, durometer ratings, grip and speed over different surfaces

Skate wheels have come a long way since the steel or clay wheels of the past. Anyone who has ridden both these and modern urethane wheels will vouch for the increased speed, better grip and overall improved ride quality of urethane wheels. This is mainly down to the ability of urethane wheels to rebound, ie return to their original shape quickly after being distorted. Modern urethane is signifcantly "higher rebound" than older urethane - you can test the rebound or a wheel by dropping it on the floor and seeing how high it bounces.

This quality is used to minimise the rolling resistance of the wheel. When you put your weight on the board, the wheels compress slightly at the leading edge as the wheel rolls on to the road, and then as the wheel roll on the back edge rebounds pushing against the road and returning the energy used to compress the wheel in to forward momentum. If your wheels were too soft they would not rebound fast enough and this energy would be lost, if they were too hard the road surface distorts slightly and tarmac rebounds very slowly, again wasting the energy. The theory is something has got to give somewhere so you might as well try to minimise the energy losses. Longboard wheels tend to be around 78-80 durometer (higher numbers = harder wheels) whereas shortboard wheels are often around 99-101. This is because shortboards are used on very hard, smooth surfaces where harder wheels are faster.

All this is also tied in with how much grip a wheel has over different surfaces. Generally speaking, the rougher the surface, the less grip you have. On a rough surface a hard wheel will be much less grippy than a soft wheel, as the soft wheel will compress over all the tiny bumbs in the road surface whereas a hard wheel won't. However, on a really smooth surface (like a concrete skatepark), hard wheels will actually have more grip than soft wheels - but when they slide it'll be a sudden snap and they'll go forever, whereas soft wheels will be much more progressive.

3.Flatspots
The dreaded flatspot happens when you slide a wheel sideways, it stops spinning and one area of it starts to wear down faster than the rest of the wheel. You know when you've got one because you'll come out of a slide and your board will make a noise like a motorbike. They slow you down and can chuck you off if they get too bad! You can avoid them by not holding your board fully sideways in a slide (powerslides and laybacks are notorious for flatspots), and rotating and swapping your wheels over sometimes helps.

4. Wheelbite
This is where the wheels hit the deck. It can be very bad as the wheel can stop, throwing you off the nose. Wheel wells help a fair bit, but you can also solve it by switching to smaller wheels, putting risers on or tightening your trucks.

5. Progressive Grip and why it's good
A wheel is progessive if it looses grip gradually. A non-progressive wheel will grip for ages, then let go into a slide suddenly. Progressive wheels tend to be more predictable over a variety of surfaces, as they're always sliding sideways a little bit, whereas unprogessive wheels are usually a bit grippier. Which you prefer is up to you - if you want sheer grip go for unprogressive wheels, but if you want to carve, drift or slide your speed off at all your better off going for something that lets yu slide predictably.