Testing Quai ISOS 33 Enduro Wheels on Italian Gravity Trails [Review]

If stiffness and durability are your top demands for a carbon-rimmed wheelset, you can have both of those things in a reasonable $1,299 package that weighs roughly 1800g with the ISOS 33 Enduro wheels from Quai.

Those of us who covet shiny carbon things often want them for different reasons. When it comes to wheels, there’s an industry narrative of stiffness and potentially lower weight that comes along with glued fibers. If stiffness and durability are your top demands for a carbon-rimmed wheelset, you can have both of those things in a reasonable $1,299 package that weighs roughly 1800g with the ISOS 33 Enduro wheels from Quai.

Setting the 33mm wide rims up tubeless is a breeze, and all of the tires I tested with them snapped into place using a simple floor pump. They come with rim tape, valves, and stickers to change the small stripe of color on the rim to match your bike. The included tape and valves work as advertised, and I have not experienced any issues with burping tires or leaking air. That wide, 33mm internal rim width gives any modern tire a nice curvature. I prefer mid-width 2.3 or 2.4″ tires, and their slightly narrower casings mount up with a shade squarer profile than they would on a narrower wheel which is always appreciated on off-camber trails.

The Quai ISOS 33 with a 2.4″ Kenda Pinner Pro mounted on the right here.

Wavelike moldings around the Quai carbon rims work alongside asymmetrical spoke holes allowing the wheels to be built with shorter spokes where they need additional stiffness while maintaining an isosceles triangle shape which reportedly results in a stronger wheel. On a traditional, symmetrically-drilled rim, spokes from the drive side of the rear hub flange are shorter than those on the non-driveside to make room for the cassette. On the front wheel, the hub flange moves inward on the non-drive side to accommodate the rotor, leaving the drive side spokes longer. With an asymmetrical rim, the spoke holes are offset to allow for roughly equal length sides of the cross-sectioned triangle they create between the hub and rim while keeping the rim centered. If you know the physics behind why an isosceles triangle is stronger than a scalene triangle please share that with us in the comments below. Is it related to the fact that the scalene is perpetually falling to one side?

Quai took this relatively common asymmetrical design a step further, making the portion of the rim where the rear-driveside spokes attach 6mm taller to get spoke tensions as close to equal as possible on either side. On the front wheel, the non-driveside spokes attach to this taller segment of the rim for the same reason. As a result, the spoke length difference on either side of the wheel is minimal. A good deal of this stiffening and spoke length shifting has been achieved on other wheels by increasing the height of the alloy hub flanges, and the Quai engineers found a creative solution that doesn’t add much weight — and does add style points.

These distinct looking circles offer some of the stiffest and most precise handling we could expect from a carbon rim. In softer soils and mud, the ISOS 33 wheels track with the precision of their double-priced competition and perform even better than some of those blingy options. For hard-hitting riders with 38mm fork stanchions who value stiffness above all else, they won’t disappoint.

The B-side of all that knife-blade stiffness and precision in unpacked trail conditions is that the ISOS 33 wheels feel skittish and unpredictable on rocks and roots. In Italian you would say si sentono nervosi, meaning they feel nervous. They truly do feel nervous and shaky when overwhelmed with obstacles in a rough rock garden. I first noticed this while riding on a dry and dusty day at Paganella Bike Park, where it felt like the rock-strewn trails were wet. My favorite grippy tires danced around from rock to rock instead of grabbing on to hold a clean line. I rode the same trails with a different bike and wheelset and found oodles more grip. After riding rocky trails in several other locations, the feeling has been confirmed.

I tested the ISOS 33 hoops with the usual variety of tires and pressures, and with legit gravity casings mounted up I’m not able to alleviate the vibrating-across-the-trail sensation. The wheels do feel somewhat less fidgety with a lighter, single-ply tire casing, but that doesn’t seem the appropriate tread nor puncture-protection for their stated enduro racing intentions. In their quest for ultimate rigidity, the ISOS 33 are a little too stiff for me, but heavier and more aggressive riders will likely love the added lateral support.

Not all carbon fiber rims are tough. These ones definitely are. I have slammed the ISOS 33 rims into countless rocks and hucked unseen gaps into square edge teeth while listening to the clang chorus of a nasty rim and rock union. Nada. The rims look and spin solidly. While they are laterally super stiff, they do have enough give that I didn’t manage to flat any tires while testing them. Some rigid carbon rims won’t deflect or ovalize enough on impact, and all of the energy usually is taken up by the tire, resulting in a puncture.

Hub engagement from the Quai wheels is fantastic, with 102 points of engagement from the MicroSpline freehub clicking into action almost instantaneously. While Industry 9 does make a hub with faster engagement, these straight-pull spinners provide all the immediacy I could want from a mountain bike hub, at a reasonable price. The bearings feel fluid smooth after several months of testing, and I would happily mount the Quai hubs on my winter slop bike without worrying about excessive bearing wear.

On a similar service note, the 28 straight pull Pillar spokes that are laced in a three-cross pattern front and rear are all in great shape after a summer of hard riding. While the wheels are due for some time in the truing stand, they spin impressively straight given how hard they have been ridden. Some similarly-abused wheels will have the tires hitting the chainstays by the end of the season, and there’s no question that the ISOS 33 Enduro wheelset is built to a high standard of quality.

Final thought

Given their high build quality and seemingly stellar hubs, I would love to see Quai make some aluminum-rimmed wheels. They have all of the important elements dialed with this set, and a slightly more forgiving material would be welcomed. Alloy rims could cut the price in half, and the weight wouldn’t have to budge much. While these wheels are possibly perfect for the hardest hitting enduro racers, lighter riders might be better served by the brand’s 1670g trail version.

You may need disc adapters, as all Quai hubs use centerlock rotor mounts.