Test Ride: Core Versus Disc

What’s the difference?

Almost three decades ago, the first urethane wheel specifically designed and manufactured for skateboarding made a smashing debut. Since Cadillac introduced this urethane donut in 1973, wheel manufacturers have experimented and tweaked urethane blends to create the perfect roll. The most recent developments in manufacturing technology have produced dual-durometer and cored wheels resulting in faster, smoother, and longer-lasting urethane formulas.

Tim Dawe, owner and founder of Electric Urethane Manufacturing, an Australian-based wheel maker, has been developing urethane technologies since 1981. Recognizing a need for a high-performance skateboard wheel, Dawe set up his country’s first urethane plant. The first sets of wheels coming off his assembly line were hand-poured using a high-speed, high-rebound, and high-abrasion-resistant formula. Electric Urethane has since been refining this formula and further building upon its first-generation wheel.

Currently Electric Urethane produces wheels for three brands: Point Blank, Electro, and Coretech. Back in 1992, Coretech began experimenting with composite, or dual-durometer, wheels. The concept for the Coretech System was developed through a need to create a superior urethane blend that is flat-spot resistant, continues to last, and rolls faster. In order to optimize these specific qualities, a gravity-poured urethane core was combined with Electric Urethane’s abrasion-resistant wheel formula, resulting in Coretech’s first dual-durometer wheel.

The manufacturing process for the dual-durometer wheel begins with the core. Using a 75D hardness urethane, the hub, like that of the tire (riding surface), is made from a gravity-poured casting. This proprietary process involves mixing the various ingredients of the urethane formula together, which hardens the wheel in the mold. According to Dawe, this chemical setting results in a hub that is less susceptible to heat produced by the spinning action of the bearings than injection-molded hubs.

Using an injection-molded process involves heating and melting the solid urethane, and then injecting it under pressure into the mold. It is then rapidly cooled and removed from the mold. Dawe explains that it’s really just a reforming of shape¿like water into ice. “This means heat from the bearings will want to reform the material, enlarging the bearing seats over time.” The major disadvantage to the injection-molded hub is that the core and the tire material are not chemically compatible. Therefore the holes in the injection-molded hub are physical locks, creating movement at the hub/tire interface.

After the Coretech hubs are manufactured and prepped, a softer 95A or 98A durometer urethane is used for the tire. Because both processes essentially use the same chemical compound in different hardnesses, along with a gravity-pour casting method, the tire and hub bond chemically together creating a one-piece, composite wheel.

About a year ago Dawe conceived an idea for a totally new dual-durometer wheel. After spending countless hours investigating why bearings blow out, he came to the conclusion that side-load forces, those acting perpendicular to the surface of the bearing, were the culprit. “We already had a suspension component, to a degree, in our Coretech hubbed wheel with the holes in the core,” explains Dawe. “So after months of thought I came up with the idea for the Disc¿a way to maximize our suspension without compromising hardness.”

The evolution from the core to the Disc wheel is seen in the geometries of the inner hub. Where the two differ are at the bearing seat; the core hub houses the bearing, and with the Disc hub, the tire material surrounds the bearing. Both hubs have a suspension component built in with holes running through their sides to allow for vibrational energy absorption.

The new Disc wheel is manufactured utilizing the same gravity-poured casting methodd as the hubbed Coretech, effectively suspending the bearings away from the direct load and vibrations of the disk. “Because the tire and hub are chemically bonded as a one-piece, two-hardness wheel, there is no movement at the interface,” says Dawe. “We can’t break our bond with a sledgehammer and a chisel, the tire material will split before the bond breaks.”

According to Dawe, the same principles hold true for vibrations associated with rolling on rough surfaces: “The wheel is noticeably faster on rougher surfaces than a conventional core.” The Disc hub supports the wheel structurally, while the holes in the hub absorb vibrations.

Dawe sent a set of 56 mm Disc and core wheels to SKATE Biz to support his claims. After riding a set of Accel. 52 mm mono-urethane wheels, I switched to the conventional Coretech core wheels.

Apprehensive at first about the whole idea, wondering how a change in the core geometry could affect so many characteristics, I rode the core wheels for about a week on as much terrain as possible. I sessioned obstacles on the sidewalk, visited the smooth asphalt of a skatepark, rolled around at Climax Manufacturing’s training facility, and even pushed through TransWorld’s parking lot (the roughest known to man).

For comparative purposes, I assembled each set of wheels in the same manner, and all had premium bearings with spacers.

Here’s what I discovered. The core wheels provided a fast, smooth roll and gripped relatively well for a hard wheel. They felt like every other hard wheel I’ve ridden in the past. But maybe that’s because I never really paid attention to my wheels that much.

But when I put the Disc wheels on my board, I noticed a difference instantly¿the Discs were faster and smoother, even in TransWorld’s parking lot. It felt like I was riding on ice-smooth concrete¿well maybe not that smooth. My point is a skate spot that normally would be overlooked because of a rough riding surface can be charged because you won’t rattle the fillings out of your teeth.

Electric Urethane has been experimenting with urethane technologies for about two decades now, and it looks like they’re on to something unique and good. For more information about Electric Urethane Manufacturing, check out their Web site: electricurethane.com.


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