VeloClub is CyclingTips’ membership program which brings us closer to our members, and connects likeminded cycling enthusiasts.
by James Huang
September 27, 2018
Photography by James Huang
TECH NEWS BROUGHT TO YOU BY BIKEEXCHANGE
Princeton CarbonWorks is the brainchild of a few mechanical and aerospace engineering graduates from Princeton University who boldly claim they can do aero carbon road wheels better than established players like Zipp, Bontrager, Hed, Reynolds, Enve, and Roval. The company’s first product is the Wake 6560 road wheelset, an intriguing design with impressive-looking wind tunnel tests and better crosswind stability than looks might suggest. But nevertheless, other aspects betray the founders’ relative inexperience in the field, and the premium pricing is quite ambitious.
Princeton CarbonWorks’ unconventional-looking Wake 6560 wheelset draws its name from the 65mm and 60mm differential rim section depth, and also pays homage to the company founders’ collegiate backgrounds in competitive rowing. According to Princeton CarbonWorks, that wavy shape basically allows the Wake 6560 to behave like a deeper-section rim in terms of overall aerodynamic efficiency, but like a shallower-section rim in terms of crosswind stability — the best of both worlds, basically.
All of this theory was put to the test at the A2 Wind Tunnel in Mooresville, North Carolina, and the published results are certainly eye-opening. According to Princeton CarbonWorks, the Wake 6560 trounced conventionally shaped wheels of similar dimensions like the Zipp 404 and the Hed Jet 6 Plus — and even beat the conceptually similar Zipp 454 NSW — in terms of “time weighted average savings.” And even better, the Wake 6560 also beat wheels that were significantly deeper, like the Zipp 858 NSW and Hed Jet 9 Plus.
What do bicycle wheels have to do with competitive rowing? Not much, really, aside from the fact that the founders of Princeton CarbonWorks have a background in the sport, but also are avid cyclists.
Granted, Princeton CarbonWorks’ two rounds of testing at A2 were hardly comprehensive, and how the Wake 6560 compares to the sizable pile of remaining competitors remains to be seen. It’s also worth noting that comparing separate wind tunnel results in an apples-to-apples way is notoriously problematic, especially without intricate details on the test protocol used, so take all of these claims with a grain of salt. Princeton CarbonWorks only tested front wheels, for example, not complete bikes.
That said, even if Princeton CarbonWorks’ results are just mostly true, it’s an impressive feat for a startup with no other experience in the segment.
Princeton CarbonWorks claims some mechanical benefits to the shape, too.
Carbon fiber is immensely tough stuff, but its mechanical properties are only fully exploited when the fibers are loaded in tension; much like a piece of rope, there isn’t nearly as much stiffness or strength when it’s loaded in compression. Each Wake 6560 carbon rim has 24 lobes, and each spoke is anchored in those lobes such that the ensuing loads help to pull the surrounding fibers taut. As a result, says Princeton CarbonWorks, the rim can be made lighter than most other aero carbon rims of similar depth without sacrificing long-term durability. Claimed rim weight is less than 490g.
The Wake 6560’s appearance will invariably draw comparisons to Zipp’s inspired-by-whales 454 NSW, and although the exact shape of the inner edge of the rim differs between the two, the theory behind the shape is similar.
That said, is Princeton CarbonWorks borrowing design elements from Zipp? That’s a tricky question to answer.
Zipp declined to comment on the matter, but a dig through the patent filings suggests that Zipp’s claim relates more specifically to an asymmetrical wavy rim shape, not the symmetrical sinusoidal profile of the Wake 6560.
The Princeton CarbonWorks Wake 6560 rims’ wavy profile strike an intriguing profile.
However, a patent for a nearly-identical wavy rim design was granted to Dimitris Katsanis in 2011. Katsanis is a long-time industry veteran who normally works in the shadows, but has had more public stints at various points in his career. Several years ago, he worked as a technical consultant for the UCI; more recently, he helped Wahoo Fitness tune the shape of its ELEMNT Bolt GPS computer.
Katsanis acknowledged holding the patent for the wavy rim concept, but also declined to go into further details on any arrangements he may have with licensees. And perhaps not surprisingly, Princeton CarbonWorks is also somewhat cagey on the origins of the Wake 6560’s wavy shape.
“Princeton CarbonWorks is manufacturing and selling wheels, and SRAM is not stopping them from doing so,” said company co-founder and COO Paul Daniels. “It’s in Princeton CarbonWorks’ interest to spend our resources developing next-level product that surpasses our competitors. If we have to pay a royalty along the way because economics dictate that’s a better decision than litigating patent law, then so be it.”
Clear as mud.
Although the origins of the wavy rim design are decidedly unclear, what’s not up for argument is that Princeton CarbonWorks has a real-life product currently on the market. The Wake 6560 is only offered in clincher form at the moment, but there are specific rim-brake and disc-brake variants. Both use the same tubeless-compatible profiles. Internal width is a modest 18mm, while external width at the rim’s widest point is 26mm.
Those rims are laced with Sapim CX-Ray bladed stainless steel spokes throughout. For the rim-brake version I tested here, Princeton CarbonWorks uses a radial front pattern and a radial/two-cross rear. Sixteen spokes are standard up front, along with 24 out back, but Princeton CarbonWorks also offers a 24-hole front option for riders that want extra durability and stiffness.
Many people will think that Zipp was the originator of the wavy-rim concept, but the idea dates back roughly a decade.
The standard hubs are rather generic, made in Taiwan by OEM specialist Bitex using slim aluminum hub shells, modestly oversized axles, and freehub bodies that are armored with steel reinforcements to prevent cassettes from digging into the soft surface. The driver mechanism uses a conventional pawl setup, with six steel pawls and a 24-tooth ratchet ring. Those pawls are arranged in two offset trios, though, so the effective engagement speed is a snappy 7.5-degrees.
Sealed Taiwanese-made TPI cartridge bearings are used all around — four rear, two front — and the end caps thread securely to the axles to help prevent creaking.
Both wheels come pre-taped from the factory for tubeless use, and extra-long aluminum valve stems are included in the purchase price, along with SwissStop Black Prince carbon-specific pads, steel-shafted quick-release skewers, padded wheel bags, and a factory printout of measured spoke tensions.
It’s common even for high-end products for actual weights to fall slightly adrift of claimed figures, but not so with the Wake 6560. My sample set came in exactly as advertised, to the gram: 655g for the front, and 840g for the rear, for a combined total of 1,495g including rim tape. Actual weight for the skewers is 86g per pair.
According to Princeton CarbonWorks, the Wake 6560’s wavy shape allows the rim to achieve the drag numbers of a much deeper rim, but still maintain the crosswind stability of a shallower rim.
Retail price for a standard rim-brake Wake 6560 wheelset is US$2,400; disc-brake versions cost an additional US$200. That seems curiously high given the inexpensive stock hubs and the questionable origins of the rim shape (although in fairness to Princeton CarbonWorks, the Wake 6560 is far less expensive than the Zipp 454 NSW). In case you’re wondering, that figure is comparable to Bontrager’s Aeolus XXX and Roval’s CLX range, and only a few hundred dollars cheaper than Enve’s SES options. Notably, all of those alternatives are equipped with custom DT Swiss hubs.
Chris King R45 hubs are available as an optional upgrade for the Wake 6560 wheels, but that pricing is even more of a head-scratcher. Princeton CarbonWorks charges a whopping US$800 for the swap — US$120 more than buying them outright at full retail, and far more than what other companies charge for similar upgrades. According to Princeton CarbonWorks, part of that cost is related to the Chris King wheels being assembled in the US, whereas stock offerings are built in Asia. But even so, it’s a tough pill to swallow.
Princeton CarbonWorks sells the Wake 6560 outside of the United States, but international pricing is based on straight currency exchange rates, and is subject to fluctuation. International buyers are also responsible for any local taxes and duties.
I tend to react to overly generous amounts of hype with a similar amount of skepticism, and let’s just say that the folks at Princeton CarbonWorks have zero doubts about the superiority of their product. But nevertheless, it’s hard to argue with what I experienced on the road, and there does seem to be something to the Wake 6560 shape.
Indeed, they’re wickedly fast in a straight line, and not in an overly subtle way. Having ridden countless other aero wheels over the years, I’d be lying if I said I didn’t notice something different about these — and not just on the first ride. I, unfortunately, didn’t do any properly objective wind tunnel testing as part of this review, but the subjective feedback was certainly very positive, and I have little reason to doubt the company’s wind tunnel claims to any significant degree.
Slab sides like this usually aren’t great in crosswinds, but the Wake 6560s are impressively stable.
As promised, the Wake 6560s are also quite stable when it’s blustery. I repeatedly sessioned the Princeton CarbonWorks wheels through my standard local crucible for rim stability, and despite experiencing a variety of wind conditions throughout my several months of testing, I came away impressed each time with how manageable these were. I wouldn’t say that the Wake 6560s were as easy to handle as shallow-section wheels when it’s gusty, especially when winds are swirling unpredictably. But they’re nevertheless more confidence-inspiring than I would have expected given the tall profile and slab-like sides.
Somewhat unusually for such a deep-section wheelset, the Wake 6560s are even very good companions when climbing: highly responsive, light-feeling, eager to accelerate. Torsional stiffness is very good, as is lateral rigidity. There’s no perceptible wind-up to speak of when attacking steeper pitches, and definitely no brake pad rub.
Speed may be the thing that people buying aerodynamic road wheels care about most — and rightly so — but bicycle wheels are dynamic and complex structures. Aerodynamic efficiency is important, as is stability and stiffness. But other factors come into play as well, and it’s here where the folks at Princeton CarbonWorks could use some more experience.
Braking performance leaves a fair bit to be desired, especially when viewed next to more advanced treatments like Zipp’s truly superb Showstopper sidewalls, or hybrid aero wheelsets that use specially treated and textured aluminum brake tracks, such as from Mavic and HED. Even with the included SwissStop Black Prince pads — unquestionably the best I’ve used for carbon rims — initial bite is only so-so on the Wake 6560’s old-school sidewalls. That improves under harder braking and when the rims build up a bit of heat, but it’d be nice if there was a more steady and gradual progression instead of the more pronounced ramp that these exhibit currently.
Braking performance in wet conditions was as you’d expect from a carbon rim with yesteryear sidewall technology, too: adequate at best, and occasionally terrifying at worst.
Whereas some more premium options utilize proprietary technology that yields tangible improvements in braking performance, Princeton CarbonWorks sticks with the status quo – and gets average results, at best.
Princeton CarbonWorks offers the usual platitudes when it comes to heat management, but certain elements of the data provided give me reason for concern.
“Glass transition temperature” is a term often tossed about when discussing carbon clinchers, and it’s worth a brief explainer on what that means. Essentially, the glass transition temperature is the point at which the resin in a composite structure begins to soften. Since it’s the resin that holds the carbon fibers together, it’s clear why a higher glass transition temperature is better than a lower one; once the resin softens, there’s basically nothing to keep the air pressure from blowing the edges of the tire bed apart.
According to Daniels, the resin used in the Wake 6560 has a specified glass transition temperature of 220°C. Furthermore, in-house testing at the company’s manufacturing partner supposedly shows that the rims only ever reach 140°C, meaning that 220°C spec should more than suffice.
However, the company’s three-step test protocol appears to include a pause in braking pressure in between each stage of testing, and previous tests by other companies have demonstrated that even short pauses in braking allow rims to shed quite a bit of heat. Perhaps more importantly, it isn’t usually during periodic braking when carbon rims fail, but rather prolonged application, which Princeton CarbonWorks’ test procedure doesn’t simulate.
JRA with the Angry Asian: The folly of rim-brake carbon clinchers
The presumption that 220°C is a sufficiently high glass transition temperature seems questionable as well. For example, Zipp engineers have supposedly measured temperatures over 300°C in steady-state testing designed to simulate prolonged and steady braking on long downhills, and assuming that scenario is more realistic, the Wake 6560 rims wouldn’t make it.
I didn’t torture-test the Wake 6560s myself for safety reasons, but I did find it at least encouraging that there was no noticeable pulsing under braking. Pulsing usually indicates a spot on the rim that’s slightly wider than it should be. It’s only slightly annoying in most situations, but also invariably where heat-related failures will occur since heat will build up more quickly there than elsewhere on the rim.
Will the Wake 6560s really hold up under prolonged, hard braking? I can’t say myself, and it could be argued that my 70kg weight isn’t sufficient to perform a reliable real-world test, anyway. But regardless, I’d personally feel more comfortable with a more rigorous test procedure.
Riders living in flatter areas less prone to heat-related wheel failures may be more willing to overlook the Wake 6560s middling braking performance and questionable heat-related durability. But even then, there are several other reasons to give pause.
Build quality is pretty good, with even spoke tensions all around and no detectable variances in true or roundness either when new or at the end of my test period. Princeton CarbonWorks doesn’t employ any strategies to even out the spoke tension between the two sides of the rear wheel, however, and the ones on the driveside display almost double the tension as those on the non-driveside — a solid recipe for fatigue-related spoke failures as the years and kilometers accumulate. A 2:1 lacing pattern would be very welcome here, and presumably easy to institute given the rear Wake 6560’s 24-hole drilling.
The stock hubs are also disappointing generic, especially given the price. They roll just fine, but the bearing spacing is fairly narrow front and rear, the bearings themselves are quite small, and the end caps don’t incorporate any supplemental seals. I experienced a fair bit of audible popping in the rear hub during the first few hundred kilometers of use, too, which often indicates that the pawls aren’t engaging as simultaneously as they should. That quieted down over time, but it was disconcerting nonetheless.
The standard hubs are built for Princeton CarbonWorks by Taiwanese company Bitex. Want something nicer? It’ll cost you. A lot.
Hub construction is very straightforward front and rear. The front hub uses an oversized aluminum axle and end caps that securely thread into place to prevent creaking.
Bearings are sourced from Taiwanese company TPI.
The rear hub uses a star-type flange on the driveside. It’s a visually appealing setup, but the overall configuration is disappointingly basic considering the wheelset’s premium pricing.
Stainless steel bars are embedded into the aluminum freehub body to help keep the cassette from digging in under load, but they don’t prevent scarring completely.
As with the front hub, the end caps on the rear hubs thread on to the axle to help keep things quiet. However, the threads were neither greased nor treated with any retaining compound. None of the end caps are fitted with supplemental seals, either. This minimizes friction, but doesn’t work as well as proper rubber contact seals at keeping water from contaminating the bearings.
Once the driveside end cap is removed, the rest of the rear hub comes apart by hand.
Although the hubs are relatively easy to service, the bearing spacing is very narrow, which doesn’t bode well for long-term bearing durability.
Note how far the rear non-driveside sits from the end of the axle.
The rear hub is fitted with a 24-tooth ratchet ring…
…but the freehub body’s six pawls are arranged in two stagger triplets, so the rear hub effectively behaves as if it was built with a 48-tooth ratchet ring for faster engagement.
In fairness to Princeton CarbonWorks, Bitex has a pretty solid reputation for durability. But even so, at this price, it’s reasonable to expect better.
I’d normally suggest the optional hub upgrade in situations like this, but the Wake 6560s are already more expensive than many competitors, and the pricing for the Chris King hubs is simply unreasonable.
I am of the mindset that aero wheels should be fast, of course, but they also need to be good wheels, period, especially at this pointy end of the price spectrum where the competition is incredibly fierce. To that end, the Wake 6560s fall short.
Braking performance is only average, there’s a big disparity in spoke tensions in the rear wheel, and as a brand-new wheel company, Princeton CarbonWorks has no legacy of build quality. If you want to nitpick, you could also argue that the 18mm-wide tire bed and 26mm-wide external rim width are behind in the times in terms of the sorts of tires that can be fitted before you being to compromise aerodynamic performance.
But the biggest demerit is simply value — or, rather, the lack of it.
At this price, there are a wealth of more enticing options out there, all with more proven track records, better support networks, more engineering resources, and superior hubs. Granted, Princeton CarbonWorks has a distinct story to tell with its sinusoidal rim profile, but even if you take the company’s wind tunnel claims at face value, that improvement in aerodynamic performance is still tough to justify from a cost perspective.
Perhaps at some point in the future the Princeton CarbonWorks Wake 6560 will be a more complete package. But that point isn’t today.
Princeton CarbonWorks claims that the wavy rim shape also provides some mechanical benefits by loading more of the carbon fibers in tension when the spokes are tightened.
Each Wake 6560 rim has 24 nodes, but the front wheel is built with just 16 spokes, so not all of them are used.
Sapim CX-Ray bladed stainless steel spokes are used all around.
The external-cam quick-release skewers require regular maintenance in order to generate sufficient clamping force. For the Wake 6560’s asking price, I would have liked to see titanium skewer shafts, too.