WTB KOM i25 27.5 Rim – First Look
Blister’s Measured Weight: 466 grams
Internal Width: 25mm
Effective Rim Diameter: 564mm
Wheel Build: DT Competition spokes / Hadley Hubs
Bike: Santa Cruz Nomad 27.5
Duration of test: 2 weeks
[Editor’s Note: After 25 days on the WTB KOM i25 rims, we’ve added an update on page 2 addressing their durability and offering more comparisons.]
Stan’s NoTubes broke new ground when they first released their Flow rim. It was much lighter than comparable rims of that width (21mm internal) and intended use. Riders flocked to it, and were rewarded with a rim that had relatively good durability, was easy to set up tubeless, and was pretty easy to build into a wheel.
And now, WTB may have a created a similar class-leading product with the new KOM rim.
It is (1) significantly lighter than other aluminum options, (2) comparable in weight to carbon offerings, and (3) it comes in at a competitive price for a high-end aluminum rim, crushing the price of carbon rims.
The old axiom is: cheap, durable, light—pick two.
So if it is both light and relatively cheap, then the KOM must give up something in terms of durability, right? And if so, how much?
My initial thought upon seeing the KOM line of rims was: “If these don’t break immediately, they’ll be pretty cool.”
I don’t tend to slowly wear out/break rims with a death of a thousand dents. Instead, I tend break about one per year during a single large impact–a mistimed bunny hop, a shorted jump, or some other error in judgment.
That could mean that the Stan’s Flow EX rims I’ve been using are overkill most of the time. If most of the time I could get away with a lighter rim—and still only replace one a year—I’d be excited.
To put the weight of the WTB KOM rims in context: the carbon fiber ENVE M70 rim that also has a 25mm internal width is $975 per rim and weighs 458g – heavier than the KOM’s listed weight, and 10 times the price.
Unfortunately, when I weighed the KOM rims, they came in at 466g and 468g. That is a pretty big difference from the advertised weight of 438g, but it’s still light enough to beat other aluminum rims, and it’s still very close to the ENVE carbon rims.
I replaced a set of Flow EX rims on my Nomad 27.5 with the KOM i25 rims. I used DT alloy nipples and DT Competition spokes to lace the rims to a set of Hadley Hubs – entirely the same components I had used when I built up the Stan’s Flow EX rims. I did this in part because those are my preferred components due to their balance of price vs. performance, but also to make the comparison as valid as possible.
The build was pretty easy and fairly comparable to building the Flow rims. Neither the KOMs nor the Flow EX rims are eyeleted, so there is a bit more resistance to turning nipples than on an eyeleted rim, but also less weight. The rim was fairly round and true – again, comparable to the Flow EX, so achieving even spoke tension wasn’t too hard.
I mounted up the same Maxxis 2.4” High Roller II tires to the KOMs that I’d been using on the Flow rims. They mounted up easily by hand, with no need for tire levers. And once on, the bead hook holds very tightly.
I filled them with a compressor after rubbing the bead with soap and water to make everything slick, and to expose any leaks. I added 1.5 scoops of Stan’s sealant for good measure.
The bead fully seated around 40psi, and on the first shot, there weren’t any leaks.
This tire-rim combination is the easiest-to-seat combination I’ve used, slightly better than the Flow EX.
I’ve been riding these wheels for about two weeks now, and they’ve held up well so far. There is a bit more perceptible flex than there was in my Stan’s rim, but I’m of two minds when I try to conclude whether that is good or bad.
One the one hand, the wheel is a bit more forgiving over rough terrain, and finds a bit more cornering traction as well.
On the other hand, they don’t give quite as much trail feel and are slightly less confidence inspiring because of the flex, but the differences are subtle relative to the Flow EX.
Additionally, the KOM rims are definitely a bit easier to pedal up the hill. They don’t have the silent, stable ride quality that carbon rims tend to have, but they are very comparable to every other aluminum rim I’ve been on in terms of noise.
I’ll be riding the KOM rims over the course of the summer to see if they continue to hold up. If they do, then then they will represent a lighter option to the Flow EX, or a less expensive alternative to carbon rims.
NEXT: Update, Comparisons, Etc.