WTB Frequency Team i25 Rims, 29”
24.7 mm Inner Rim Width (measured)
561 grams (measured)
Mounted to: Industry Nine hubs / spokes, Canfield Yelli Screamy frame
Rider: 5’9” 150 lbs.
Duration of test: ~30 rides
Test Locations: Whitefish & Missoula, MT; Spokane, WA
WTB has been making rims for quite a while, and these days, you’ll most commonly find them as an option on custom built wheels from a shop, or as an aftermarket replacement if you trash a rim. WTB does offer some pre-built wheels, but they’re somewhat lost in the sea of wheels that are offered these days.
I laced up the Frequency Team i25 rims to my Industry Nine Enduro wheels, which originally came built with Stan’s Flow EX rims. After about 30 rides, the WTB rims are still dead true and rolling smoothly.
Some Stats on the Frequency Team I25, 29” Rim, plus a Quick Comparison
Since WTB rims are often going to see use as an aftermarket option, here are some helpful numbers on the 29” version of the Frequency Team i25’s that might help if you’re looking at lacing up some new wheels or slapping a new rim on some old ones:
Effective Rim Diameter (ERD): 599mm
29.5mm Outer rim width (measured)
24.7mm Inner rim width (measured)
561 grams (measured)
Max tension: 125 kgf (range: 110-125 kgf, with 120 kgf recommended)
As I mentioned, these i25s are replacing some Stan’s Flox EX rims. The WTB rims are almost exactly the same size as the Stan’s—they’re slightly wider and slightly heavier, but otherwise almost identical. Here are the stats on the Stan’s:
Effective Rim Diameter (ERD): 601mm
29.3 Outer rim width (measured)
25.2 Inner rim width (measured)
544 grams (measured)
Max tension: 125 kgf
Since the WTB and Stan’s rims have almost the exact same ERD, I was able to re-lace my wheels with the WTB rims using the same spokes.
The i25 rims are a pretty straight forward, no frills rim. They do sport a vertical brace that runs through the middle of the rim, which is (as far as I can tell), a unique feature to WTB rims.
All Frequency Team rims have what WTB calls “4D Drilling,” which means the spoke holes are drilled at an angle to help the nipple sit flush against the rim. In theory, this means that the nipple spreads the stress coming from the spoke in an even contact patch around the hole in the rim, which in turn allows you to put more tension on the spoke without overstressing the rim in the area right around the spoke hole.
Most wheel builders will have over-tensioned a rim at some point in their career, which (usually) leads to cracks in the rim around the spoke holes. Traditionally, this has been addressed by either (1) using lower spoke tension, or (2) putting eyelets in the rim which help spread out that spoke force. The problem with running lower spoke tension is that you end up with a less stiff wheel, and the problem with eyelets is that they add a bit of weight and they cost more to manufacture.
So does WTB’s 4D drilling do the same thing as eyelets, but at a lower weight and cost? I can’t say for sure without doing some destructive testing, but it certainly doesn’t hurt anything.
The joint on the i25 is sleeved, which is one of 3 methods of joining a metal rim – the others are pinning and welding. Pinning a rim involves a “tube” that’s extruded into the rim’s profile. At the joint, dowels are inserted into these tubes and the rim is pinned together. The upside to this process is that it’s relatively inexpensive. The downside is that the “tubes” add a bit of weight to the rim since they run the entire circumference of the wheel.
The joint on welded rims is, obviously, welded. This produces a very strong joint that’s also probably yields the lightest construction. The downside here is that 1) it’s more expensive to do, and 2) it means an area of the rim has been subjected to high heat, which can make that area brittle, warped, and require more heat treatment to correct, but that brings us back to downside #1: it’s more expensive to do so.
A sleeved joint, like that used in the i25, is relatively common. It bears some similarities to a pinned joint, but there’s no need for a special rim extrusion to accommodate the pins; a chunk of metal is manufactured to fit precisely into the joint area of the rim, and it is then bonded in place. This type of joint is generally going to be slightly heavier than a welded joint. It also can be a bit weaker. However, to be fair, not all welds (and therefore not all welded rim joints) are created equal; some may be stronger than others. And many of the rims that are in the same price range as the i25 use a similar sleeved joint,
The rims are made out of “WT69” aluminum alloy, which appears to be a proprietary WTB thing that is claimed to have “a 20% higher yield than 6000 series Aluminum alloy.” I admit to being a bit skeptical of these sort of claims, but that doesn’t mean there’s anything wrong with the metal used in the WTB rims.
Most aluminum mountain bike parts, rims included, are made from either 6000 or 7000 series Aluminum. There’s a bunch of variants within each series that are the result of using slightly different mixtures of metal – in practical applications, aluminum is pretty much always an alloy, meaning that there’s a variety of other stuff like magnesium, silicon, zinc, and maybe some other elements mixed in. There’s also different heat treating grades that differentiate some of the alloys. The result of this is that different alloys have different properties; some are harder (often at the cost of being more brittle) while others might be more ductile. And of course, the price of these alloys comes into play as well.
So, getting past this brief tangent, I can’t verify the veracity of WTB’s claims regarding their rim material. I have ridden a few rims that were light, but very obviously made out of some softer alloy. I generally refer to those as race rims because, while the lack of weight is really nice, they don’t hold up to abuse very well at all. Those rims are great for people that take racing really seriously or have deep pockets and like rebuilding wheels. I’m neither of those.
The i25 rim and the WT69 alloy don’t fall into this “light but extremely fragile” category, but I’m getting ahead of myself…
TCS Tubeless System
The i25 rims feature what WTB calls “TCS,” which stands for Tubeless Compatible System. In practical reality, this means a couple different things. First and foremost, it means that these rims have a UST bead profile.
UST is a tubeless and sealant free system that was pioneered by Mavic – the rim and the tire are designed to work together, and if you use a UST certified rim with a UST certified tire, you’re supposed to be able to run it without tubes and without sealant (actual results vary a bit).
WTB’s TCS system isn’t fully certified UST – you still have to tape the rims and use sealant. But the rim profile is UST compliant, which means that UST and TCS certified tires lock into the rim bead really tightly.
In more specific terms, the rim has a little nub that sticks up and keeps the tire bead from getting (easily) pushed inward. The idea being that in hard corners when the tire is getting folded over and the bead is trying to pull away from the sidewall (which would allow air to escape), that little nub will help hold everything in place.
This idea is a good thing; I’ve been somewhat lukewarm on the whole tubeless thing because I find that I burp and blow off tires with just enough regularity that it’s really annoying. The TCS system seeks to solve this problem – pinching the tire bead in really tightly helps prevent burps and blow-offs, and in my experience, it seems to work really well.
My completely un-scientific empirical testing shows that I get better results with the i25 TCS rims than I did with the Stan’s Flow EX rims (which don’t have any sort of bead locking profile). On a high-speed huck-to-off-camber-flat, I burped a WTB Vigilante tire on the Stan’s rim. On the exact same drop with the exact same tire, ridden in the same manner, I didn’t burp the tire when it was mounted on the i25 rim. That’s only one example, but there have been plenty of similar situations where I came to similar conclusions.
So what does this mean for using a TCS rim with a non TCS/UST tire? It probably still helps, but it might not help as much. The TCS tires have a bead dimension that mates up with the TCS rim, but that certainly doesn’t mean that other tires are incompatible, it just means the bead might not be locked into place quite as securely.