What do we talk about now that the whole wheel size argument is starting to cool? Screw diameter, let's talk about width. It seems like everything on bikes is getting wider these days and rims are no exception. Mountain bike rims have been 19- to 23-millimeters-or-so-wide for decades now. By the way, when talking about rim width we'll always refer to the inner width because it is the dimension that makes the difference in ride quality. Outer rim width is an arbitrary number. Anyway, rims have slowly been gaining a millimeter or two, but this year we're seeing most brands hop on the width wagon.
So what's the point? And why now? Well, wider rims increase volume and tire stability, so you can potentially run lower air pressures and get better grip. They also locate the bead of the tire out farther, giving the sidewalls more stability. This concept isn't new. Some of the first mountain-bike-specific rims were actually pretty wide, but they were heavy. In an effort to make things lighter, rims eventually became narrower. But manufacturing is much more advanced than it was back when guys were racing converted beach cruisers down fire roads in Marin County. Perhaps it's time to re-discover why wider is better.
Specialized started its house brand wheel company, Roval, around 2005. You'll see Roval wheels spec'd on many of the company's bikes, but they're also sold aftermarket. The first few years were rough for Roval. The wheels were pretty horrible, frankly speaking. I was wrenching for Specialized when they were first launched. Having previously worked at Mavic, the then-dominating rim and wheel company, I remember how bummed I was when these Stan's knockoff Roval-branded wheels showed up for the race bikes. Nearly 10 years later, though, I can confidently say that the Roval mountain-bike wheels are pretty damn good. We've abused a couple sets of Control SL wheels over the past couple seasons without a single broken rim, spoke, or even a truing.
Roval Traverse SL Fattie
The new Traverse SL Fattie is, as the name states, fat. The hookless carbon hoop comes in 650b and 29-inch diameters and sports a 30-millimeter inner width, which is said to optimize the advantages of a wide rim and weight. According to Specialized, going wider offers diminishing returns since ride quality is affected by weight, and the wider you go, the heavier things get. OK, that makes sense.
At 24, and 28 spokes front and rear, respectively, Traverse SLs have a pretty low spoke count for a wheel built for aggressive riding, but they don't ride flexy. Those wide-ass rims are stiff enough themselves that it was possible for the Roval team to reduce the spoke count and still meet strength requirements. They're built with lightweight but ultra-reliable DT Revolution straight-pull spokes.
DT Swiss also provides the rear hub guts, Star Ratchet, which is one of the most proven freehub systems on the market. All the parts are laced, tensioned and trued by hand, because as amazing as wheel-building machines are these days, a human touch still wins. Weights are claimed to be 1,570 grams for the 29ers and 1,530 in 650b. These weights are taken without rim strips or valve stems. We didn't weigh them ourselves because being a weight-weenie is a terrible existence and we don't want to live that way.
At $1,400, you can take a set of these bad boys home for only $400 more than a single solitary ENVE rim, and each aftermarket set comes with four decal color options. Roval stresses that the Traverse SL is a top-tier product, despite the competitive (for carbon) price point.
The wheels accelerate far better than the hefty-looking rims suggest, and they're tough too. I've been smashing through rock gardens on these things for several rides now and have managed to pinch flat a tire and bottom out HARD a half dozen times or so without a single nick in the carbon hoop. This is thanks in part to the hookless rim wall. Most rims have a hook for the bead to catch on, but a few years ago Specialized started experimenting with a hookless design. After all, motorcycle and car wheels don’t have bead hooks, so why should bikes? The theory worked, and now hookless rims are being adopted by other brands. It allows for a cleaner, stronger carbon layup and reduces or eliminates the need for machining the carbon after molding.
If you do manage to break a rim, a new one is only $125 plus labor. Specialized will charge $80 for labor if it goes back to its facility in Salt Lake City, but will allow dealers to do handle rebuilds too if they choose. Shops typically charge $40-$80 for a wheel build. As for stiffness, I have no complaints so far. I swapped out a set of DT 240/ENVE M70 wheels for the Traverse SLs and didn’t feel any recognizable performance difference.
What about this whole wide rim thing, then? Well it definitely makes a difference in tire stability. I've been running Specialized Control casing tires, which are too thin for aggressive riding, but that's what was installed on the wheels when I got them so I'm running them. If you're an aggressive rider, you'll want to use Specialized tires with Grid casing. Again, the Control tires are too thin and flimsy, but they have far better cornering stability on the wide rims. When I return home, I'll put some proper casing tires on and start experimenting with tire pressures. From my initial riding though, I think it's safe to say that in general, you can run 2-5 psi lower on the Traverse Fatties. Keep in mind though, that individual experience will differ based on riding style, preference and terrain.
All and all, it seems like the wider rim is a good move. While it won’t make you a better rider, the benefit can certainly be noticed. I wouldn’t run out immediately to buy a set of wider rims, but if you’re in the market for wheels, the Traverse SL is definitely worth considering.