Sea Otter 2011: Easton's new EC90XC wheelset

Superlight carbon UST cross-country wheels

Easton don’t back their new EC90XC carbon fibre cross-country wheels with the same two-year, no-questions-asked warranty as their — and the industry’s — first UST carbon wheelset, the all-mountain Haven Carbon. But the new superlight wheels share the same technologies and materials, and are said to be similarly durable.

The EC90XC comes in both 26in (US$2,500) and 29in ($2,600) versions, weighing 1,280g and 1,420g respectively (actual weight for front and rear wheels with valve stems but no skewers). The cost will make many balk, but understanding the engineering and labor that's gone into making the wheels goes a long way to explaining it. Should they prove as durable as claimed, the high price may be justified.

Manufacturing process

The rims are molded and assembled into wheels at Easton’s EMX composite factory in Tijuana, Mexico, which is outfitted with sterile clean rooms used for carbon molding. Producing the wheels in-house rather than outsourcing the work to the Far East gives Easton total control over design and manufacturing – and it also ensures the security of the proprietary materials used to make the rims. The relative proximity of the 65,000sq ft facility to Easton's Californian headquarters (compared to a factory in Asia) also allows engineers easy access should they need to be on site during development.

The key to Easton’s carbon wheels is their proprietary Armored Ballistic Composite (ABC) material. This is made up of carbon fibre and high-modulus polyethylene held together with a MRES-B (Multifunctional Resin/Epoxy) polymer resin. It was developed by Sayeed Syed, a former defense industry carbon engineer, who now serves as the head of Easton’s composite research and development team. ABC is also used to make body armor and helmets, due to its ability to absorb impact shock, in many cases without damage.

We rode the EC90XC on Ibis's new Mojo SL-R 140mm trail bike with WTB Bronson tires in 2.3in (front) and 2.1in (rear) sizes

Easton say the material is the single biggest contributing factor to the Haven and EC90XC wheels’ strength and durability. “We saw a lot of other manufacturers taking the same composite that they were using for their road wheels and putting it into a mountain bike shape to make a carbon mountain bike wheel,” said Adam Marriott, Easton’s wheel product manager. “But right off the bat you’ll notice that there are a lot of different demands on a mountain bike wheel than there are on a road wheel. The main one is that there’s no heat and there’s more impact due to low tire pressure and rocks. That led us down the path [of reasoning] that the composite that we’re using for the road isn't the correct composite to use on the mountain bike side.” 

The new rims have a 19mm inner width, 24.7mm outer width and 21.8mm height. Easton use their carbon molding process to precisely orient material, adding more to the tire bead hooks for strength and impact resistance, and thinning the layup in the UST (Universal System Tubeless) trough to reduce weight. The company make a big deal about the EC90XC’s UST profile. The standard demands very precise manufacturing and UST wheels must pass tolerance and strength tests not required of tubeless-ready wheels. The payoff, according to Easton, is that by using the licensed profile, their rims offer less hassle and more consistent tire mounting as well as more security once mounted. The wheels can be used without sealant when used with UST tires.

The rim's tire bed is UST licensed

The hub side of the rim features four different angles for the spoke holes, which precisely align both drive and non-drive, pushing and pulling spokes. After the rims are molded they’re fitted with special threaded alloy riv-nuts that the proprietary nipples then thread into. “This [design] can convert between aluminum and composite, that’s the beauty,” said Marriott. The riv-nuts are reverse threaded so that the nipples thread into the riveted nut and onto the spoke simultaneously, always either loosening or tightening. This design allows the use of standard straight-pull Sapim spokes — which allow higher tension — and doesn’t require the inner rim wall be punctured or any special tools be used to install the nipples or true the rim.

The wheels’ straight-pull flange spacing and four-angle rim drilling means that the same length spokes can be used on both front and rear wheels, and on both drive and non-drive sides. Since each wheelset only requires one length, only a few spare spokes are needed for emergencies. Replacement is made very easy by the straight-pull design; neither cassette nor brake rotor needs to be removed to install a new spoke, which isn't the case with standard J-bend spokes. “By aligning the spoke with the hub, it offers better fatigue life of the spoke itself since there are no kinks or bends,” said Marriott. The 26in wheels are fitted with 20 spokes front and rear, while the 29in set relies on 24 front and rear. Both wheels are laced three-cross and use 2.0/1.7mm double-butted spokes that Easton feel best balance weight and stiffness.

Easton's riv-nut and proprietary double threaded nipple

Easton build the wheels by hand and acoustically tune each one during the finishing process. “Every wheel we make is entirely hand-built every step of the way,” said Dain Zaffke, Easton’s cycling brand manager. “They’re not hand checked, they’re hand built. The acoustics allow them to get to a really even accurate spoke tension, quickly. That’s the heart of it; it’s a really fast way to get to an even spoke tension.” Because the builder can be sure that the tension is even across all of the spokes, a higher tension can be used (keeping tension even is particularly important for low-spoke-count wheels). Tension is double-checked with a tensiometer to confirm what the builder is hearing.

Hubs are CNC machined, anodized and fitted with double-sealed ceramic cartridge bearings. The front hub is compatible with 9mm quick-release or 15QR through-axles; however, the axle must be replaced in the conversion. The rear hub’s cassette body is made from 7050 alloy and features a three-pawl system with 36-point ratchet ring that offers a 12-degree engagement. The rear hub is compatible with standard quick-release dropouts, as well as 12x135mm and 12x142mm through-axle systems via end caps.

Easton's EC90XC hubs feature a three-pawl system with 12-degree engagement; front and rear hubs are equipped with double-sealed ceramic cartridge bearings

In addition to the work Easton do in their Mexican factory, each wheel model is tested extensively at their Scotts Valley headquarters to make sure it can copy with a variety of scenarios, including edge impact, bump fatigue, drive torque fatigue, stiffness and full wheel impacts. Both the 26in and 29in wheels will be available for sale from 1 May 2011.

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