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by Matt Wikstrom
August 3, 2015
Photography by Matt Wikstrom
At present, riders looking for a high-end wheelset for a road disc bike must contend with a variety of incompatible standards and a limited range of products. As a custom wheelbuilder, Curve Cycling is equipped to hand pick components to suit a rider’s (or bike’s) specifications. In this review, CTech editor Matt Wikstrom assesses Curve’s vision for a lightweight disc-equipped wheelset.
For those that haven’t been introduced, Curve Cycling is a Melbourne-based company largely devoted to performance-oriented wheelsets. Steve Varga is in charge of product development and invested a lot of time auditioning carbon rims before he found an Asian supplier that suited all of his needs.
Curve’s stock wheelsets use high-end components like DT’s robust 240s hubs, Sapim’s CX-Ray semi-bladed spokes, and Sapim’s secure lock alloy nipples. For road use, there’s a choice of 38mm or 50mm carbon clincher rims that are tubeless compatible and UCI-approved for competition use.
For those riders with specific needs and tastes, Curve offers a custom wheel-building program. Options include mixing rim profiles, varying spoke counts, and custom coloured decals. In addition, buyers can supply their own hubs or consider other brands such as Tune and White Industries. There are also options for tubular rims and road disc brakes.
The latter may be controversial, but there is clear enthusiasm for the format from within the industry. Whether or not disc brakes are ever adopted for competition remains to be determined but they offer a number of distinct advantages. Indeed, by transferring the heat of braking from the rims to rotors, disc brakes are an ideal match for carbon rims.
Early road disc adopters will find that the current range of performance-oriented wheelsets is limited. There is also a variety of rotor and hub standards that must be carefully matched before the wheels can be fitted to any given bike. Standard quick-release axles versus through-axles; 135mm versus 142mm hub spacing; six-bolt rotors versus Centre Lock; 140mm versus 160mm rotors. Satisfying any given combination can be difficult, more so when weight is a priority, but this is the kind of challenge that custom wheelbuilders are well equipped for.
As I was preparing Colnago’s new V1-r disc frameset for review, I encountered one of those difficult combinations, but Steve Varga wasn’t perturbed. With a lightweight 24mm disc-specific carbon rim on hand, he set out to create a Curve wheelset to suit the frameset.
There were three firm requirements for this wheelset. First (and most obvious), disc compatibility; second, the front hub had to accommodate a 15mm through-axle with 100mm spacing; and third, the rear hub needed a standard quick-release axle with 135mm spacing. Such specifications are relatively common for MTB wheels, so Steve had a variety of high-end cross-country hubs to choose from including DT’s 240s hubset, White Industries CLD hubs, and Tune’s King/Kong hubset.
It was the latter that captured Steve’s attention because of its low weight.
“Tune have been a reliable, lightweight choice for our weight conscious builds,” he explained. “They look great, are fairly simple and have the ‘Made in Germany’ quality appeal. I really like that they use ‘real’ materials internally like steel pawl springs not rubber o-rings as a pawl spring to save weight. That is worrying for bike owners who actually like to ride their bikes.”
Tune’s King/Kong hubset utilises oversized 17mm hollow alloy axles that can be converted from standard quick-release fittings to through-axles. For the front King hub, that means compatibility with a 15mm through-axle, while a 12mm through-axle can be mated with the rear Kong hub.
The hub bodies are precision machined from aluminium alloy, as is the freehub body, and titanium is used for the teeth and pawls. Disc rotor compatibility is strictly six-bolt and there is a choice of eight finishes (silver, black, red, gold, orange, froggy green, green and blue).
As for the rims, Curve’s disc-specific 24mm carbon clinchers are 23mm wide with a 16mm bed and weigh 360g each. The rim is also tubeless compatible like Curve’s other carbon clinchers.
I’ve already discussed some of the special requirements for road disc wheels, where the number of spokes and lacing pattern must be robust enough to resist braking forces at the hub. Most hub manufacturers recommend a minimum of 24 spokes with a two-cross lacing pattern, and that was what Steve elected to use for this build.
Opting for the minimum number of spokes will save some weight but it places an extra demand on the spokes.
“You definitely need sound spokes,” said Steve. “Sapim CX-Rays have a very high tensile rating and very little flex width ways, so are great for light disc builds.”
Interestingly, CX-Ray spokes are also lighter than plain gauge round spokes; the only downside is that they cost at least three-times more than round spokes.
I’ve always had a weakness for anodised hubs so there was plenty of appeal in the final build. The overall aesthetic is clean and simple and Curve has kept their decoration of the rim to a minimum to help the understated appeal of these wheels. It’s worth noting that the orange hubs required some extra time to arrive from Germany, but I think they were worth the wait.
The final build weighed 1,346g with rim tape sans skewers (622g for the front wheel, 724g for the rear wheel) and retails for $2,799 in Curve’s webstore. For more information including warranty details, visit Curve Cycling.
From my first moment on the bike, Curve’s road disc wheelset was a fine match for the Colnago V1-r. Light, stiff, and very responsive, the wheels were as exciting as they were easy to ride.
The first thing I noticed was how ready the wheels were to move. Any lightweight rim will endow a wheelset with the same ease, and any rider will revel in the sensation. Of course, it’s a trait that is felt most keenly on any slope, more so for steeper ramps. The lack of inertia fools the senses into thinking that much less effort is required to the point of inspiration. It’s the kind of edge that any rider is looking for when they buy a new set of wheels, and it was clearly on offer with Curve’s wheelset.
Curve’s carbon clincher rims are rigid. It was something that stood out for me when riding Curve’s 38mm carbon clinchers earlier this year, and it was almost as evident with the 24mm rims. However, where the 38mm rims could become harsh on rough roads, the 24mm rims remained smooth and comfortable (I used 23mm tyres throughout this review). In short, they were more versatile than the 38mm rims and much easier to recommend for daily riding and long outings.
I weigh around 75kg and have a modest power output, and at no stage did either ever challenge Curve’s 24mm rims. My “sprint” was captured and translated with ease. At times I might have suspected I was using taller rims but one look down at the front wheel was enough to shatter that illusion. So I tried to stack the odds in my favour by challenging a sharp 10% slope with a slow cadence while out of the saddle, and still the wheels refused to yield.
There’s no point in dwelling on the individual traits of a wheel, because it’s the combination that ultimately determines the performance of the wheelset. For Curve’s 24mm disc wheels, the lightweight rim combines with the stiff, efficient carbon layup to create an exceptionally responsive wheelset. As a result, there were times where I found myself quickly under-geared when I put in an effort. Ultimately, my top speed remained the same, but I often felt like I was able to get there quicker when riding these wheels.
The low profile rim was never troubled by the wind, and as I’ve already mentioned, it was also comfortable enough to ride on any road surface. As for braking, I had the benefit of SRAM’s hydraulic RED 22 groupset, which offered a sure, immediate response, regardless of the conditions.
A low profile carbon rim is a common choice for a lightweight climbing wheel, but with a minimum of material to serve as a heat sink, the rims that are best suited for climbing are also the worst choice for descents where conventional rim brakes are concerned. Disc brakes dismiss this issue almost entirely. Weight-weenies may object to the extra weight associated with the rotors, but as I’ve noted previously, it doesn’t detract from the performance of the wheels.
Curve’s 24mm disc-specific wheelset has a lot to offer—light, stiff, highly responsive, comfortable, and versatile too—but there is more on offer, because it is also customisable. Buyers can consider other options for the hubs, spoke count and colouring for the wheelset. All will have a bearing on the final price, but the cost is still very reasonable when compared to other high-end wheelsets, disc-equipped or not.