Curve Cycling Belgie Spirit titanium all-road frameset review

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The all-road/gravel sector may still be in its infancy, but shoppers are already spoilt for choice. Not only is there an array of brands and construction materials to choose from, but subtle variations on a common theme make for a diverse collection of framesets and bikes. Be that as it may, Curve Cycling has managed to bring something new to this sector in the form of an affordable titanium frameset, the Belgie Spirit.

In this review, Australian tech editor Matt Wikstrom takes to a mix of paved and unpaved roads to learn what the Belgie Spirit has to offer.

Curve Cycling started life as a small venture between two riding buddies, Steve Varga and Jesse Carlsson. Steve had an interest in product development, especially wheels, and spent more than five years exploring the range of composite rims on offer from Asian manufacturers before Curve Cycling launched its first wheelsets in 2013.

Curve’s offerings have evolved in the time since then, partly due to a growing stake in product development. Where once the company was sourcing stock rims
from a reputable supplier, it has since been able to collaborate with a trusted manufacturer to develop more sophisticated carbon rims.

Curve adopted the same cautious and studious approach when it became interested in adding a frameset to its catalogue. Its first offering, dubbed the Grovel, was a small-run crowd-funded creation targetted at a fresh niche in the market, gravel/adventure-riding. In retrospect, it’s easy to label the decision as a canny choice, but it was simply driven by the interests of the riders that populate Curve.

The early iterations of the Grovel were all made from steel, an affordable and robust material well suited to the demands of unpaved riding, but Curve was convinced titanium had more to offer. Over the next few years, the company explored the options open to it — factories and frame builders in various parts of the world — before settling on a frame builder in China who was able to accommodate all of Curve’s needs, including an amount of affordability.

All of the frames in Curve’s current catalogue are now made from titanium. The Grovel has morphed into the Grovel CXR, a cyclocross/adventure bike that sits in the middle of a spectrum of offerings ranging from the Belgie, a dedicated road chassis, to the all-terrain GMX.

The candidate for this review, the Belgie Spirit, rounds out Curve’s drop-bar collection by offering buyers a road-going bike that can contend with the demands of unpaved roads. Curve doesn’t refer to the Belgie Spirit specifically as a gravel bike, though; it’s an all-road bike that can accommodate tyres up to 35mm wide.

Before the ride

Titanium has a reputation as an exotic material due, in part, to the high cost of the metal. However, it is also more difficult to work with than steel, requiring specialised tools and welding conditions, all of which add to the cost of the final product.

For Curve, the extra expense is justified. “Titanium simply works for us as the optimal solution,” said Adam Lana, Curve’s brand and sales director. “It has the best all-around properties for most types of riding. Steel is close but can have a weight penalty.”

There are other aspects to the appeal of titanium, such as its relative plush ride quality, which Lana counts as ideal for endurance riding. He also sees value in the durability of the material, which is arguably more robust than carbon composites, especially when tackling challenging terrain and/or travelling with the bike.

The Belgie Spirit is constructed from Grade 9 titanium alloy that comprises 3% aluminium and 2.5% vanadium (which is why it’s also commonly known as “3/2.5”). It’s a time-proven alloy that is favoured by frame builders because it is easy to weld yet retains much of the high strength for which titanium is known.

The front triangle of the frame makes use of double-butted tubing while the rear triangle employs straight gauge tubes. The head tube, bottom bracket, and dropouts are all machined from Grade 9 titanium.

As mentioned above, Curve makes use of a frame builder in China to create all of its frames. “We are proud of the workmanship that goes into our frames,” said Lana. “The welds and quality say it all, so we are happy to talk it up.”

The frame features a T47 threaded bottom bracket shell and an oversized 44mm-diameter head tube, both of which can be readily adapted to suit a wide range of cranks and forks, respectively. The frame is equipped with a flat-mount for the rear disc calliper and a 160mm rotor along with a 12mm thru-axle for the rear wheel. As for groupset compatibility, the Belgie Spirit is offered in two versions: one to suit mechanical groupsets, and another for powered derailleurs.

Working with a frame builder affords some flexibility, and while that doesn’t extend to custom geometry, buyers can elect to add rack and/or fender mounts as well as an extra bidon mount under the down tube for a small upcharge (AUD$70-90).

The frame is paired with an all-carbon fork with a tapered steerer. Like the frame, it provides a flat-mount for the front disc calliper and makes use of a 12mm thru-axle. There is also internal routing for the front brake hose.

All of these features sit well with an “all-road” bike and there is enough clearance for tyres as large as 35C. At its core, though, the Belgie Spirit is a road bike specifically designed for 700C wheels and tyres ranging 25c-32c. For those that want or need larger tyres, Curve believes the Grovel CXR is a better choice.

The Belgie Spirit frameset is available in six sizes, as shown in the table below:

The stack is generous for each frame size while the reach is relatively short, which will suit buyers hoping for a more relaxed, upright position. Chainstay length ranges 418-428mm, increasing with frame size, while the bottom bracket drop decreases (73-68mm). A single fork rake of 45mm serves all frame sizes.

The Belgie Spirit is supplied in a largely unfinished state, leaving all of the raw metal on display for an exotic effect that should appeal to purists. The lines of the frame and fork are clean and simple while Curve’s branding is subtle and easy to overlook. The titanium seatpost and clamp that are supplied with the frameset add further to the exotic feel of the bike to the point where the final, classy, result defies its relatively modest asking price.

I’ll discuss the price in a moment, but first, the weight: the 54cm frame sent for review weighed 1,630g without the thru-axle or seatpost clamp, while the uncut fork weighed 408g (sans thru-axle). Those numbers won’t light up a weight weenie’s imagination, but they are very respectable for a metal frame with a mandate for all-road use.

Once assembled with a SRAM Red eTap HRD groupset with a Quarq DZero powermeter (supplied by Monza Imports), Curve’s Grav AL alloy wheelset, 3T alloy cockpit, and a Fabric saddle, the final weight of the bike was around 8.6kg (18.96lb), without pedals or bottle cages, depending on the tyres that were fitted. Once again, another respectable result for a bike that essentially eschews carbon fibre.

Now, the price: at AUD$3,599 (~US$2,710/€2,300/£2,030), the Belgie Spirit is quite a bargain. Curve sweetens the deal a little by including a headset, titanium seatpost, titanium seatpost clamp, and thru-axles with each frame and fork. Also included with the Belgie Spirit is a “lifetime” warranty (specifically, 37 years) for the frame and a five-year warranty for the fork.

It is worth noting that while Curve holds some stock of the Belgie Spirit at its Melbourne headquarters, the lead time for any order is generally 6-8 weeks, and that period will increase for those adding extra options or pursuing a custom bike build. For more information on the Belgie Spirit and all of the options on offer, visit Curve Cycling.

After the ride

Curve labels the Belgie Spirit as an “all-road” bike, promising that it “will glide through mixed road surfaces, allowing you to travel further and faster in style.” When coupled with a capacity for tyres up to 35mm wide, the bike promised to be a versatile performer, so I set out to ride the Belgie Spirit on every sort of road I could find with a variety of tyres to see where its strengths and weaknesses lie.

My tyre choice comprised 25C and 28C road clinchers (Clément LCV and Vittoria Rubino Pro, respectively), 30C and 35C all-road tyres (Schwalbe G-One tubeless), and a set of 33C cyclocross tyres (Schwalbe Racing Ralph). The Belgie Spirit was able to accommodate them all, though the 35C tyres were a close fit.

Unsurprisingly, tyre choice had a big impact on the capabilities of the bike. The bigger tyres provided the necessary comfort and grip for rough terrain while the narrow tyres lowered the bike and afforded extra speed and agility on paved roads. Schwalbe’s G-One tubeless tyres ultimately proved to be the most versatile choice and I spent the majority of the review period using 35C G-Ones for tackling a mixture of road surfaces.

The larger tyres were not only more versatile, I found they suited the demeanour of the Belgie Spirit. The bike was a rambling adventurer rather than a race-tuned speedster, so a set of narrow tyres simply worked more to highlight its shortcomings rather than lift the overall performance.

The geometry of the mid-sized 54cm frame I was riding accounted for a lot of this demeanour. Up front, there was a very slack head tube angle (71.5°) while the rear triangle was pretty generous (420mm chainstays) for a road-going bike. Factor in the tall stack of the bike and the short reach, and the Belgie Spirit was quite removed from a conventional road bike.

Those numbers translated into a bike that lacked the punch and agility of a typical road bike. The steering was slow and heavy, and while the bike was very stable at high speeds, it took a lot of effort to change my line. Minor corrections were also a challenge, so there were times when I felt like a captive passenger dearly hoping for more control over the direction of the bike.

The small mounds under the tape are SRAM’s Blips, remote shifter buttons for the wireless eTap derailleurs.

The Belgie Spirit was not a stout frame, either, so on paved roads the bike suffered from some very obvious flex under load. As an all-road bike designed for comfort and versatility over anything else, a lack of race-tuned stiffness is both understandable and forgivable, but it’s worth stressing the point: the Belgie Spirit is not an energetic race bike.

Swapping to wider tyres not only did a lot to disguise these shortcomings; the bike was also more ready and willing to explore unpaved routes. With 40psi in the 35C G-Ones, I could transition from paved to unpaved surfaces with ease, and the bike would perform and respond in much the same manner.

The slow and heavy steering was still a handicap. Yes, the Belgie Spirit remained remarkably well mannered at high speeds, but with a need to dodge rocks, holes, and ruts at short notice, I found myself longing for more manoeuverability. In addition, the bike was prone to wheel flop at low speeds (e.g. when climbing), so it had a tendency to wander about unpredictably. This effect wasn’t so noticeable on the road, but on unpaved roads, I found myself having to work at correcting the direction of the bike.

Curve supplies a titanium post and clamp with the Belgie Spirit.

The rear end of the bike also gave me some problems. On paved roads, it wasn’t short enough to help the responsiveness of the Belgie Spirit, while on unpaved surfaces, it wasn’t long enough to stop the rear wheel from skipping around and breaking traction when I was out of the saddle.

The juxtaposition of an over-reactive rear end with an under-reactive the front end unbalanced the overall feel of the Belgie Spirit (at least for the size that I was riding). What the bike really needed was a fork with more rake (e.g. 50-55mm) and longer chainstays, although this may be less important for larger frame sizes, which have a steeper head tube angle and longer chainstays.

With all of that said, I was able to adjust to the Belgie Spirit within a couple of weeks, and in many regards, those shortcomings started to go unnoticed. The bike simply demanded a forceful touch and a lot of extra body english in some settings. While there was some reward in getting the bike to respond in demanding situations, in the back of my mind, I still would have preferred a bike that required less effort to control.

I’ve already mentioned there was some flex in the chassis, and while it undermined the sprinting prowess of the Belgie Spirit, it afforded a generous measure of comfort. The bike was always smooth and silent on paved roads. With a set of narrow tyres, I could also enjoy some of the distinctive feel that I’ve come to associate with titanium, but the bike didn’t hum in the same way that other titanium bikes can, such as Legend’s Il Re or Wittson’s Suppresio.

That compliance translated to unpaved roads, and with a generous tyre like 35C G-Ones, I was able to tackle some gnarly terrain without being overwhelmed by shock and chatter. There was a limit, though, to how much comfort the Belgie Spirit could provide. For example, rocks and long corrugated stretches of unpaved road consistently defeated the bike, but I know from past experience that this is the kind of terrain where high-volume tyres (eg. 700 x 50C or 27.5 x 2.1”) are more effective than a compliant frameset.

I’ve used SRAM’s eTap on the road before but during the course of this review, I found a fresh appreciation for the groupset while riding on unpaved terrain. The powered derailleurs truly minimised the amount of effort required when shifting so that I was able to stay focussed on controlling the bike.

In this regard, SRAM’s remote Blip shifters were outstanding. They are easy to locate and use by feel, even when the bike was moving around a lot on uneven terrain. With that said, the Blips require a reasonably precise touch, so there were times when I missed a shift because my finger was not centred on the button. Nevertheless, I appreciated the positive action of the Blips and I found myself making greater use of the shifters and the gear ratios at my disposal. Now I’m starting to think that an electronic groupset may be indispensable for a gravel bike.

By the end of the review period, I had spent almost four weeks on the Belgie Spirit, with a largely even split between paved and unpaved roads. In retrospect, I may have been a little rough on the Belgie Spirit by venturing into areas far more demanding than what the guys at Curve had in mind when designing it. The bike was always a willing accomplice and that it was able to contend with it all (save for a few pinch flats) has to be counted as a promising sign. And once I washed away all of the dust, the bike looked just as good as it did when I first put it together.

Summary and final thoughts

Curve’s Belgie Spirit fulfils what is rapidly becoming a widespread vision for a road bike, namely a comfortable and adaptable chassis with disc brakes that can accommodate a generous range of tyre sizes. In the past, the Belgie Spirit might have been labelled a touring frame; today, it is classified as an all-road frame. The distinction is probably a matter of semantics but for those shoppers looking for a well-priced, robust, and versatile frameset, the Belgie Spirit should have a lot of appeal.

The bike suffers from something of an identity crisis, though. On paved roads, the Belgie Spirit is smooth and steady but it isn’t as stiff or agile as a typical road bike. On unpaved roads, the stable handling inspires some confidence at high speeds, however the heavy, unresponsive steering undermines the manoeuvrability of the bike. In addition, the rear end is too short to provide the kind of steady traction that is necessary on undulating terrain.

With that all said, the Belgie Spirit can be ridden hard in a variety of settings but the rider will have to work at it. For some, such man-handling might add to a sense of connection with the bike, but for those looking for the confidence to tackle unfamiliar terrain, the Belgie Spirit may fall short.

What do each of the individual ratings criteria mean? And how did we arrive at the final score? Click here to find out. You can also read more about our review process.

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