Fulcrum Racing 5 CX Wheels

by Paul Horta-Hopkins · 02/11/2012

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Fulcrum Racing 5 CX Wheels Preview

2nd November 2012

Words by Tim Granshaw

Tim prepares to get down and dirty with a cyclo-cross specific wheel set – the Fulcrum Racing 5 CX

I’m a good 5 kilos off my best racing weight but I still crave the lightest go-fast components, and I’m obsessed with a few grams or millimeters here, a flared dimple there. Deeply dished, strangely profiled flying saucers with aero spokes and trick hubs have supplanted the simple 28-spoke, 3-cross Mavic GEL280s of my youth.

After such an admission, you might think it a little strange that I’m intrigued by the Fulcrum Racing 5 CX wheel set as they aren’t the lightest wheels at 1760 grams for the set, nor do they claim to be the fastest; and they are far from the most expensive even at the £229.99 recommended retail price. In fact, though they look nice with white hubs and stylish graphics around the rims, you wouldn’t think of them as distinctly different from any other mid-range aluminium race and training wheel.

So why am I intrigued and what makes them special? Well firstly, every Fulcrum wheel, from the top-of-range XLR carbon wheels to the most affordable Racing 7 set, are built by hand. After the build, computer checks ensure that each wheel is not offset in any plane, shows consistent spoke tension, spins freely, and is appealing to the eye.

Most wheels in this price range rely on machine builds with human error checking. The reason is purely economic: machines can build wheels in minutes, while a hand build takes much longer. These time savings don’t come without compromises: advocates of hand built wheels will tell you that machines struggle most with proper spoke tensioning. Proper spoke tension is important because it ensures that broken or loose spokes and wheel wobbles are eliminated.

Secondly, the rear Fulcrum Racing 5 wheel is an unusual beast. Trying to make a strong rear wheel has haunted wheel builder’s dreams since the advent of geared bicycles. Unlike the front hub, the rear hub is asymmetric: the hub is shoved to the left to accommodate the cassette to the right. This offset results in differing spoke tensions between the two sides, compromising strength.

The rear wheel also takes far more punishment being burdened with 70% of the rider’s weight and power output, resulting in far higher stresses at the back wheel than at the front. Fulcrum has built their rear wheel around resolving this historical problem, with an innovative approach comprised of three tenets:

1. The hub: the hub uses a larger flange on the drive side than the non-drive side. This means a shorter spoke length on the drive side, decreasing wheel dish. This is a less unusual aspect of the build as several manufacturers already use asymmetric flange heights.

2. The spoke ratio per side: the rear wheel features 8 spokes on the non-drive side and 16 on the drive side for a total of 24. Most wheels have a symmetric number of spokes with 12 per side. Fulcrum maintains that by adding drive side spokes it increases total spoke tension on the weaker drive side of the wheel, improving lateral wheel strength and stiffness.

3. The spokes: the spokes on the Fulcrum Racing 5 are hammerhead or straight, with the squared spoke head slotting into a similarly squared spoke hole before fastening to alloy spoke nipples at the rim. The consensus among wheel builders is that a straight pull spoke allows for a higher spoke tension. J-bend spokes are prone to snapping at the bend if over-tightened.

In another interesting move, two of the spokes per wheel are a heavier gauge and silver. This additional weight ensures wheel balance, offsetting the valve drilling. The different coloured spokes also serve as a marker when trying to locate your presta valve before pumping up your tyres!

You’ve probably noticed a theme: the rear wheel has been designed with spoke tension, strength, and durability in mind. The front wheel, in comparison, is a standard design, featuring 20 straight pull spokes in a radial pattern with alloy nipples.

There are two Fulcrum Racing 5 wheel sets with this CX-designated wheel sporting a more robust bearing seal than its road sibling. Rather than a single gasket, the CX wheel includes a double-gasket design. This seal ensures the bike destroying cruelties of cyclo-cross racing stay far away from the Campagnolo-inspired bearing surfaces. Although these wheels are positioned as cyclo-cross specific, this design might make sense for any rider looking for a tough all-weather training wheel.

The rim appears a much more standard affair. Lower profile than the Racing Quattros tested here previously on CycleTechReview.com, the rims appear to be a well-built, well-finished design. The braking surfaces are nicely-brushed, smooth and deep, and the reinforced eyelets look reassuringly durable.

The wheels first ride, except for a quick spin down the road, will be an upcoming cyclo-cross race – straight from the pan into the fire for this wheel set. Look out for our full review soon.