In Review: Princeton CarbonWorks Grit 4540 Gravel Wheels
You’ve probably not heard of Princeton CarbonWorks, but with its first products, the company is sure to make a splash.
The company founders know each from collegiate rowing at Princeton University. Armed with college degrees and having switched to triathlon and cycling, the two set out on a quest for a new and better wheel in terms of performance and cost. That eventually led the two to develop the Princeton CarbonWorks Wave 6560, a rim profile that has sinusoidal waves that vary the rim depth from 60 to 65mm.
Princeton CarbonWorks claims reduced spoke hole stress and improved aerodynamics as advantages, the latter proven by the founders in the wind tunnel. We will not get into the engineering and physics of those claimed benefits, but you can read Princeton CarbonWorks’ explanation here.
At first glance, you might think the rim shape is a copy of Zipp’s 454 NSW rim shape, but while the theory might be similar, the execution is different:
The Grit 4540 is a new Princeton Carbonworks model based on the success of the Wave 6560 but aimed squarely at the gravel rider. The number refers to the sinusoidal rim depth, varying from 40-45mm.
The rim design has improvements, most notably the solid carbon tire bed. Eliminating the inner spoke holes yields a stiffer rim, so the team re-engineered the layup optimizing weight and durability. The best part is the lack of holes eliminates the need to tape the rim for tubeless sealing. We’ve enjoyed such a setup with the F.S.E. G40 carbon gravel wheels as well. On the other hand, in the unlikely event a spoke breaks and you lose the nipple in the rim, it’ll be a challenge to re-thread the nipple into the hole.
The Grit 4540 is available for either rim or disc brakes with White Industries or TUNE hubs in your choice of axle configuration. The TUNE hubs will save some weight (about 100 grams total) and cost the same.
Our review set of Princeton CarbonWorks Grit 4540 came with White Industries CLD (center lock disc) black anodized hubs. The CLD rear hub has a titanium freehub body that resists the bite of loose cassette cogs with a minimal weight gain over aluminum. There are 3 pawls and 48 ratchet teeth. We have the Shimano/SRAM standard freehub body. The White Industries CLD hub is available with a Shimano Microspline, SRAM XD/XDR, or Campagnolo body.
The Grit 4540 rim has a sinusoidal profile with 24 waves, the rim depth varying from 40-45mm with the spoke holes at the deepest section (the peak of the wave). The internal width is 22mm hook-to-hook. The profile has a 1cm depth (average-top of the rim wall to the bottom of the channel) with a prominent bead shelf that has a bead retaining lip. The outer width is maximally 30mm. An internal width of 22mm is not wide by standards now, but wall-to-wall under the hook it is 23mm. The claimed rim weight is 415 grams for the disc version and 430 for a rim brake version. Hub choice will impact wheel weight, which is neither claimed nor published.
Twenty four black Sapim CX-Ray flat section stainless steel spokes lace the 4540 rims in a two-cross pattern to the White Industries CLD hubs. Sapim Secure Lock nipples keep things tight. Spoke tension is tight and even. Princeton CarbonWorks hand builds the wheels to order in Connecticut. Our set was completely true and round out of the box.
The measured weight for our review wheelset (no valve stems) is 697 grams front, 829 grams rear for a total of 1526 grams. The included 60mm valve stems are 5 grams apiece with the aluminum nut and flat o-ring.
I found tire mounting easy without the tape and with the prominent bead shelf with its retaining ridge. I certainly recommend a bit of soap water with tighter tires to aid the bead sliding up onto its perch, since the carbon rim surface has a bit more friction than tape.
I tried a loose tire first, the Teravail Cannonball 38, then the Ritchey Megabite. Both went on smoothly (with a compressor) and did not fall off the bead shelf when deflated. A floor pump inflated tighter tires- the example I used is the ERE Research Tenaci Tubeless 36mm. The two 38mm tires measured true to size, the ERE Tenaci has a 92mm bead to bead measurement and it rests at 35mm on the 22mm internal Gravel 4540 rim.
Deflated tires remain sealed and on the bead shelf, a sign of tubeless reliability. I did not find the removal of the tire to be burdensome, as can be the case with a tight tire and a high or sharp bead retaining lip.
Just an ounce over 1500 grams is a great weight for a stoutly spec’d and built wheelset with a fairly deep section. The weight can be sub-1500 with the TUNE hub option at no additional cost. The self-claimed wind tunnel performance with the improved cross wind performance puts it ahead of other choices in the aero category. The lack of rim bed spoke holes is a boon for tubeless tire mounting and the notion of improved rim integrity and stiffness makes sense. A 22mm internal width with a hooked rim is also good for road tubeless applications and narrow tires of 28-30mm optimize the aerodynamic profile. I would not recommend a tire as narrow as 25mm. It would not offer aerodynamic advantages, nor would offer much rim protection.
I’ve only taken the new wheelset for a few rides on our typical mixed terrain test courses. The most remarkable note is the appearance they give the bike when at a standstill. When spinning, no one sees the difference, including the rider (who should be looking ahead anyway). Perhaps I’m not going fast enough to appreciate the aero advantage I could be having, but the Grit 4540 does feel light enough for spirited acceleration and climbing when compared to other categorically similar wheels with similar tire choice. I’ve not yet had enough cross-wind experience to ascertain the advantage of the 5mm depth change of the sinusoidal profile in that situation compared to other 40mm deep rims.
Over rough terrain in the few rides so far, there are no quality or durability concerns at all. There is no question that wheel ‘stiffness’ in cornering on and off-road is excellent. That is a hard parameter to gauge considering tires and tire air pressure, as well as surface conditions. The same goes for ‘comfort’ which includes vibration damping. However, it is noteworthy that a wheel that is not adequately ‘stiff’ is detectable. The Princeton CarbonWorks Grit 4540 is fine in both categories with the so-far limited assessment.
So far, I think in the case of the Grit 4540, the theoretical mechanical advantages afforded by the rim design yielding a light strong rim is the big appeal, followed by the aero advantage and unique appearance. This is a well spec’d wheelset with high-quality components and excellent build quality.
There is a 30-day test ride guarantee from Princeton CarbonWorks that is full money back, no-questions-asked.
In the same price range, you could get lighter but arguably less aerodynamic with Industry Nine’s latest option, or with the lightweight Roval Terra wheels. Easton’s EC90 AX and EC70 AX wheelsets offer gram and dollar savings.
A long-term review assessing further advantage of the wavy rim design (durability and real-world aerodynamics) is in order, so stay tuned.
Grit 4540 wheelset Specifications:
MSRP: Grit 4540 wheelset, $2800 USD
Weight: 697 grams front, 829 grams rear (1526 grams), Princeton CarbonWorks variable depth sinusoidal cross-section rim 415 grams (list)
Width: 40-45mm depth, 30mm outside width, 22mm inner width hook to hook
Hubs: White Industries CLD hubset, Shimano/SRAM Ti freehub
Spokes: 24 X2 Sapim CX-Ray spokes, Sapim Secure Lock nipples
More info: princetoncarbon.com