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The introduction of carbon fibre rims more than two decades ago ushered in a new era of aerodynamic wheel design. In the time since, rim profiles have been refined and updated, but laminated construction processes have remained largely unchanged. FSE (Filament Spin Evolution) has been working on a new approach — filament winding — for composite rim production, and while it has taken five years, the results are impressive. In this review, Australian tech editor Matt Wikstrom puts a set of FSE’s filament-wound carbon clinchers to the test.
In the eyes of many, carbon fibre products embody a lot of cutting-edge technology yet the actual method of construction is really no different from Papier Mache, which is centuries old. In both instances, layers of overlapping strips of material are moulded together with some kind of adhesive to form a laminate that is far stronger and more robust than the individual components.
It’s a simple construction process that allows irregular shapes to be formed but it is prone to defects. Any gaps (or voids) that occur between the layers of material become a point of weakness for the final structure. The application of pressure during the construction process (in the form of vacuum-bagging and/or autoclaving), or more recently, the use of pre-impregnated materials, improves compaction of the layers, but it doesn’t eliminate the risk of voids altogether.
An alternative is filament winding. Decades old, it’s a process that involves wrapping a continuous length of fibre back and forth over a mandrel to create what is typically a length of tubing. The fibre can be run through a resin bath as it is applied to the mandrel for even impregnation of the material, and by keeping the fibre under tension as it is wrapped, all voids are dispelled.
Filament winding is readily automated, so the reproducibility of the process is much higher than what can be achieved by labour-intensive hand-lamination. However, it is largely limited to regular shapes and linear profiles, so it can’t be used to create all parts of a frame or fork. And up until recently, it had never been used for bicycle rims.
Dan Kellerby came to filament winding via a very roundabout journey. He grew up on an Oklahoma farm obsessed with two things — bikes and guitars — and became a self-confessed shop-rat in both realms before his talent for music won out. He moved to Nashville where he had a successful career as a songwriter, sound engineer, music producer, and partner in a small music label until downloadable music overhauled the industry and Dan re-discovered his passion for cycling.
By this stage, Dan had sold his label, and decided to draw upon his passion for cycling to drive his next entrepreneurial effort. He established a consumer-direct online shopping mall to sell frames, wheels and other components made by Chinese manufacturers. It was early in the new millennium and the market for these products was on the upswing but he quickly discovered that the quality of the products from different factories was very uneven. He conducted his own quality control, which included cutting up the frames, to decide which manufacturers were worth representing.
The business was a success and after selling off that company, he was invited to work on the design and marketing for carbon rims by his most trusted Chinese manufacturer. “They mentioned they were developing a new carbon fibre rim using a completely new process and I asked, is it filament winding? It seemed we had been reading the same technical documents.”
What followed was a lengthy development phase. According to Dan, “The initial drive for this project was to find a way to have automation provide 100% accurate quality control and to make a superior rim. The project team decided it was best to do a complete rethink of the process for making carbon fibre rims, including the ingredients, and filament winding was part of that solution.”
The first patents for the new process were lodged in 2012 and by late-2014, prototypes were ready for road testing. Dan anticipated that the rims would be stronger and lighter due to improvements in the efficiency of construction, but the results collected over the next year consistently exceeded his loftiest expectations. By the time FSE formally launched its range of filament-wound rims at Interbike in 2016, he found himself in the uncomfortable position of making what seemed like some pretty extravagant claims.
“I cringe some when I make big statements like 40% stronger and stiffer,” explained Dan. “In fact, the number is higher. We also make the lightest carbon rim that is at least 24mm wide: again, a big claim. I hope people don’t think I’m just blowing smoke.”
FSE is not content to trumpet the merits of the new rims and wheels though. In the ultra-competitive wheel market, where new start-up brands rise and fall on an annual basis, the company has priced its products for mass appeal. For example, the company’s 25mm wheelset, weighing just 1,198g for the clincher version and 1,030g for the tubular version, is currently selling for US$995 (~AUD$1,315).
Buyers have a lot to choose from FSE’s current catalogue since there are six rim profiles (25/35/45/55/69/79mm) and a variety of drillings (16/20/24/28/32 holes) with versions to suit clincher and tubular tyres as well as rim- and disc-brakes. In short, FSE seems to have something for everybody, be it dedicated weight-weenies or weekend warriors pondering their first carbon wheelset.
Before the ride
The whole notion of a filament-wound rim is mind-boggling, and while I had a lot of questions for Dan Kellerby, there was only so much information he could provide while protecting his company’s investment in its manufacturing processes. Thus, I have no idea how the rims are actually created, but Dan was able to give me some sense of the effort involved.
“Massive warehouse-sized high-tech computer-controlled machines had to be invented from the ground up,” he said, “because the in-place methods of filament-wound carbon would not work for bicycle rims.
“The production line spans several large warehouse rooms. The carbon fibre thread creels are tension-controlled as they head to the resin-bath. Then they head to the winding machines themselves. No carbon threads are cut or broken and voids are completely eliminated. EPS [expanded polystyrene] mandrels are later compressed and pulled away after the rims have cured. The critical parts of the process are automated, including the spoke-hole drilling.”
FSE is an original equipment manufacturer (OEM) and used laminated rims from its own production line as the benchmark for judging the strength and stiffness of the filament wound rims, so it’s unclear whether the 40% improvements extend to all carbon rims on the market. Nevertheless, the company is confident in the strength and stiffness of its rims. For those that take the time to visit FSE’s website, there is a video of Dan bouncing a tubular wheel — without a tyre — on a concrete floor. While this does little to prove FSE’s claims, it’s clear the rims aren’t fragile.
Rim weights are impressive, too. For example, FSE reports that its 25mm tubular rim weighs 262g while the clincher version weighs 372g. That easily bests Enve’s 2.2 (tubular, 287g; clincher 424g) and Zipp’s Firecrest 202 (tubular 315g; clincher 418g). In absolute terms, there is a lighter 25mm carbon tubular rim on the market (195g, ax-lightness) however it is not as wide as FSE’s rim (22mm versus 25.6mm) and it sells for a lot more.
FSE opted for a rounded profile for its new rims that is similar to the semi-toroidal shapes made popular by Zipp, Hed and Enve. When asked about aerodynamic performance, Dan Kellerby said computer-based aerodynamic tests were run but no wind-tunnel testing had been completed. This testing is scheduled but until then, he doesn’t know how FSE rims compare with the market leaders. “Aerodynamics are very important to us,” he said, “and we will never stop improving our wheels.”
The company’s top priority was to create a robust brake track for the new clinchers. According to Dan, “We reached out to university research departments, chemical corporations and technical institutes to develop a new resin with the highest glass transition point (Tg) in the industry. The result is a resin that is stable and transparent past 240°C.”
That’s no guarantee that the brake track won’t overheat with prolonged braking but the rims pass FSE’s testing protocols. One test involves at least 50 cycles of braking for 80 seconds at 13km/hr with a 70kg load on the wheel, while another is performed at 58km/hr with the same load and 5,000 cycles of braking in three-second intervals.
FSE provides its own pads with the wheels, however they aren’t a strict necessity. Buyers are free to use any other carbon-specific brake pads without worrying they will void the company’s two-year warranty.
Looking more closely at the EVO 35C clincher wheelset sent for review, the 35mm tall rim was 26.5mm wide with 18mm in between the rim beads. This is a wide carbon rim, so it may not fit some older framesets, but for those that can accommodate 28c tyres, there shouldn’t be a problem.
With 20 spokes in the front wheel and 24 spokes in the rear wheel, the EVO 35C is clearly performance-oriented, plus it’s UCI-approved (as are the 45C and 55T wheelsets). The wheelset has a weight limit of 250lb (113kg) and a maximum tyre pressure of 130psi (9bar) however it is not tubeless-compatible (though FSE has had success converting rims with undrilled beds for tubeless use).
Some may be quick to dismiss FSE’s 260 SL hubset as an economical option, but it’s very light (front, 71g; rear, 185g), besting many well-known brands. At the same time, it’s clear that plenty of thought has gone into the geometry. The low flanges of the front hub are broadly spaced to improve the overall lateral stiffness of the wheel while the rear hub is purpose-built for triplet lacing.
For the uninitiated, triplet lacing requires twice as many spokes on the drive-side of the wheel. While this is a relatively uncommon design, it has been in use for over two decades because it does a lot to alleviate the difference in spoke tension associated with the asymmetry of the rear wheel. The tension on the non-drive-side spokes is normally half that of the drive-side spokes for a conventional wheel, but in the case of triplet lacing, it can be much higher.
In this instance, there was almost even tension on both sides of the EVO 35C rear wheel (drive-side, 135kgf; non-drive-side, 115kgf). In the context of the majority of wheels on the market today, this counts as something quite extraordinary. In the short term, it won’t offer buyers anything tangible, but over the long term, it should prolong the life of the spokes by reducing the magnitude of loading and un-loading that occurs with every turn of the wheel.
FSE makes good use of computer-controlled rim drilling to match the spoke holes to the angle of the spokes for the front and rear wheels. This is one of those finishing touches that improves the quality of the final build and reduces the risk of spoke and nipple fatigue.
Sapim’s CX-Ray spokes and Polyax alloy nipples are used to lace the wheels for a final weight of 1,350g (front, 606g; rear, 744g) including the rim tape but no skewers. This puts the wheelset into the same league as Campagnolo’s Bora Ultra 35 and Zipp’s 202 NSW clinchers without the same premium in pricing. Buyers looking to save more weight can opt for the 25C rim paired with either FSE (1,198g claimed weight) or Extralite hubs (1,058g claimed weight) while I suspect weight-weenies will be seriously tempted by the tubular 25T wheelset that weighs 888g when built up with Extralite hubs.
The presentation of the wheels is clean and stealthy. FSE incorporates its wheel logos into the weave of the rim for an understated effect. Some may recognise the wavy dress weave as the same found on Curve’s new rims, and to a lesser extent, Mavic’s latest high profile carbon rims. After so many years of 3K weave and unidirectional carbon finishes, the new pattern makes for a refreshing, even eye-catching, change.
The EVO 35C carbon clincher wheelset sells for US$1,045 (~AUD$1,390) via FSE’s webshop with free delivery to any part of the world. Interestingly, there is a second version that sells for an extra US$100 that features rims without holes drilled in the bed that FSE says is suited to tubeless conversion.
Importantly, local taxes and duties are not included in this price, so this will add to the final price of the wheels for buyers outside of the U.S. (Australian buyers, should expect to pay an extra ~15%). For shoppers that prefer to deal with a bricks-and-mortar retailer, there are a handful of North American stores that stock FSE wheels, but that is the extent of FSE’s current retail network at the moment.
All of FSE’s wheelsets are supplied with a two-year warranty along with a choice of a Shimano/SRAM or Campagnolo freehub, two pairs of brake pads, and a pair of external-cam skewers. For more information, visit FSE.
After the ride
From the outset, FSE’s EVO 35C carbon clinchers promised to be a responsive wheelset that could be used in all weather conditions, including strong winds, and that’s exactly what I found. In short, there were no surprises, no revelations, just a sound lightweight wheelset that was easy to ride.
But to start at the beginning: it was a simple matter to fit tyres to the wheelset. I used two sets of tyres during the review period, Clement’s LCV in a 25c size, and 28c Vittoria Rubino Pro tyres. A 18mm wide rim bed typically ensures that any tyre will inflate to at least its stated width, and it can often end up a little wider. For example, once installed, the 25c LCV tyres measured 26mm at 60psi.
First impressions count for a lot when I install a new wheelset on a familiar bike. In this instance, the EVO 35C wheelset struck me as quite firm with plenty of radial stiffness. This was something that was consistent throughout the review period, yet it was never overwhelming. Instead, it added to the sense that the wheels were robust, rigid, and well-suited to race-day efforts.
The other strong first impression related to the agile responsiveness of the wheels, which wasn’t really surprising given their low weight. As such, they are bound to impress most buyers with the ease of acceleration, and when coupled with the obvious radial stiffness of the wheels, FSE’s EVO 35C wheelset is likely to add an edge to any road bike.
Anybody that has made an effort to assess the performance of a wheelset will understand that most of the time, there isn’t much to judge. What registers is contrast, and that depends on changes in the terrain, weather, and/or the amount of effort the rider is making. Most of the time, the performance of EVO 35C wheelset was unremarkable, but when there was a change in the status quo, it remained largely unperturbed, sure-footed and well mannered.
Changing the tyres from 25c to 28c did a lot to smooth out the ride quality of the wheels. That ongoing sense of rigidity that I described above was largely lost with the change, so buyers can decide how much feedback they want from the wheels when they choose their tyres. This, of course, applies to any wheelset, though in absolute terms, the amount of difference that any rider can expect will be a matter of nuance.
A 35mm rim profile is typically low enough not to be troubled by crosswinds, and that was largely true for FSE’s EVO 35C wheels. Be that as it may, there were a few times when I noticed the tug of a crosswind, however it was always a fleeting sensation. I wouldn’t hesitate to use these wheels in strong winds or gusty conditions.
The EVO 35C wheels were well-suited to climbing. Low weight means low inertia, so any time my speed started to drop on the slopes, it wasn’t very difficult to get them turning again. As good as they were, I was left wondering how much better the 25C or 25T wheels could be.
The quality of braking was good. FSE’s pads provided plenty of bite when needed in the dry, though once wet they weren’t nearly as effective. As a result, I needed to allow for extra braking distance, however I never felt like I was on some kind of runaway train when trying to slow the bike in the rain. With the freedom to use any carbon-specific brake pads, I’d be tempted to test a few brands to see if I could find one that performed better in the wet.
During the final stages of testing, I spent some time swapping between different wheelsets including Campagnolo’s Bora Ultra 35s and my own custom-built HED Belgium alloys. On the scales, there was no more than a 200g difference in weight between these wheelsets, and out on the road, it was hard to distinguish one from the other.
I weigh around 77kg and my power output is quite modest, so I can’t place the same kind of demands on the wheels as a heavier and/or more powerful rider. In the absence of this, I can only guess at the suitability of these wheels for big riders, but at the very least, I’d suggest a custom build with a higher spoke count and/or taller rims for those that have trouble with wheel flex and brake-rub.
I’m not a fan of external-cam skewers because they typically require more effort to secure and offer less bite on the dropouts. That proved to be the case for the FSE skewers supplied with the wheels. At the same time, the cam assembly had a habit of getting caught in the dropout while I was locating the axle, adding extra fuss to the whole process.
For those wondering about the amount of buzz coming from the freehub, it was quite loud, but I never found it annoying or tiresome. I expect it’ll satisfy most riders that enjoy a rich buzzing from the rear wheel, while those hoping for a silent mechanism will have to look elsewhere.
By the end of the review period, I found it was very easy to take FSE’s wheels for granted. With a relatively low asking price, there’s no good reason to reserve these wheels for special rides or races, but for those that swap them out for a set of heavier training wheels, they will get to re-discover their snappy agility again and again.
Final thoughts and summary
Many cyclists will be familiar with Keith Bontrager’s maxim, “strong, light, and cheap, pick two”, and in most circumstances, it holds true. FSE seems intent on challenging this notion, because its filament-wound wheelsets seems to deliver on all three fronts without any compromises.
Unfortunately, it is well beyond the scope of this review to assess the durability of the EVO 35C wheelset, so strictly speaking, the strength of the wheelset remains unproven. FSE may not be well known in the marketplace, however its wheel manufacturing experience stretches back to 2008. A lot of this experience is on show in the thoughtful design of the rear wheel that achieves a better balance of spoke tension than all of its competitors.
Only time will tell how good FSE’s wheels truly are, but if they prove to be as hard-wearing as they are cheap and light, Bontrager’s maxim is likely to re-apply as the brand starts charging more for its filament-wound wheels.