Handlebar, stem, and seatpost specialists 3T unveiled two new road wheel collections prior to the start of this year's Giro d'Italia. While that market is highly competitive and arguably already saturated, the Italian company have still managed to instill a number of technical features that set them apart from their peers.
The all-carbon Mercurio LTD 60 features an aero-profile 60mm-deep, 23mm-wide tubular rim whose shape is said to be, "optimized for stability in the random airflow of real-world conditions." What's more interesting, however, is how the straight-pull spokes are anchored in the rim. Rather than use conventional spoke holes, 3T have incorporated T-shaped pockets directly into the sidewalls and reinforced the surrounding carbon structure with radiating fibers that 3T technical director Richard McAinsh says acts like the supporting members of a suspension bridge.
"We considered the spokes in tension as an integral part of the composite lay-up," he told BikeRadar. "Within the laminate we have a unidirectional ‘truss’ structure distributing the spoke tension load into the wall of the rim and connecting each pocket. Imagine a suspension bridge with the road suspended from the tension cables. Now bend that into a ring. That gives a picture of the structural configuration of the rim."
3T integrate these pockets directly into the mold so there is no post-production machining or cutting of fibers required. The outer rim wall is left totally solid – save for the valve hole, of course – further increasing rim strength and rigidity and providing more surface area for improved tire adhesion. The slots are also aligned specifically for each particular wheel drilling to keep the spokes perfectly straight when tensioned.
From a mechanic's point of view, 3T's unique setup allows the wheels to be trued without having to remove the tires, and both the front and rear wheels use a single spoke length.
"There are no holes in the rim apart from the valve hole," said McAinsh. "As a composite engineer I try and avoid drilling holes in composite whereever possible. You place all those fibers so carefully than cut them with a hole – that’s not so clever. The pockets are aligned to the hub machining allowing the spokes to be perfectly straight. That’s a big expense for us going forward as each spoke configuration needs a dedicated rim and hub. The rear rim for example is handed by the tangential pockets on one side and the radial on the other."
Interestingly, McAinsh also says that testing at both the San Diego Low-Speed Wind Tunnel and at the Mercedes Petronas facility in the UK also confirm that the open slots have no negative effect on drag. Surprisingly, those slots also don't serve as overt failure points as 3T say the new wheels have already passed the UCI's impact tests.
In addition, 3T say a Formula 1-derived brake track coating yields nearly identical friction coefficients in both wet and dry conditions.
3T use straight-pull spokes on the new Mercurio LTD in an inverted configuration with the threads located in snowflake-like aluminum hub flanges to reduce wheel inertia – and if they look familiar, they should. McAinsh says that 3T purchased the intellectual property behind the inverted nipple design from Cane Creek, who stopped producing road wheels several years ago.
"Having a ‘bulletproof’ hub design to work with cut that development time from our program," McAinsh admitted. "Our suppliers invested in some pretty sophisticated five-axis machining to get the precision we needed. We produce the hubs ourselves to get the control over the complete program we wanted. We have also set up our own build facility."
McAinsh says current Mercurio LTD 60 rims weigh between 385-395g each and complete wheelsets are, "under 1,400g."
3T also plans to release 40mm and 80mm-deep Mercurio versions soon.
Complementing the new Mercurio tubulars will be the Accelero clincher range, to be offered in 60mm and 40mm-deep variant. The top-end Accelero LTD will use an all-carbon rim with the same spoke slot technology as on the Mercurio; the Team will use a carbon-and-aluminum rim; and the Pro level wheels will use all-alloy rims.
Projected retail price for the Mercurio LTD 60 is US$2,300; pricing for the Accelero range is still to be determined.