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We talk quite a lot about how wheels can fundamentally alter the character and performance of a bike. This is true; it is not hyperbole, as anyone who has thrown a pair of very nice wheels on a bike that previously had very average wheels can confirm.
That good wheels enhance the enjoyment of riding a gravel bike is therefore a given. But what’s a good wheel? What’s it made of? That’s a much harder question to answer. It’s too big to answer in any definitive way for everyone.
We set out to investigate one very specific part of the equation: rim material. Carbon vs aluminum. If all else is equal (or as close as we could reasonably get), would the difference be noticeable? Would we prefer one over the other?
Two nearly identical wheels, except for rim material
After casting about for a few options for this little test, we settled on two pairs of Easton wheels, one carbon and one aluminum. The EC90 AX and EA90 AX both use the same spokes, same hubs, same lacing. The only difference is the rims, which are nearly identical other than the material. The EC90 uses a carbon rim, and the EA90 uses an aluminum rim. The EC90 is also twice the price.
EC90 AX: US$1550
Weight: 1481 g
Depth: 21 mm
Internal width: 24 mm
External width: 31 mm
Spokes: 24 Sapim straight-pull, double-butted, laced 3x
Hubs: Easton Vault
EA90 AX: US$800
Weight: 1634 g
Depth: 21 mm
Internal width: 25 mm
External width: 29 mm
Spokes: 24 Sapim straight-pull, double-butted, laced 3x
Hubs: Easton Vault
The carbon version has a slightly narrower internal width (1mm) and slightly wider external width (2mm), but are about as close as you’re going to find between two rims made of different materials.
This isn’t a perfect science. I didn’t do a hundred runs on the exact same course on both wheelsets, and the testing wasn’t blind. I just swapped between these wheels for three months, often back-to-back, on an aluminum Trek Checkpoint that is my primary groad machine.
I ran the same 40 mm-wide Donnelly Strada USH tires on both, at the same pressures most of the time – 37 psi front, 41 psi rear for my 150 lbs (68 kg). Surfaces ranged from smooth pavement to rough singletrack, but the majority of time was spent on compacted dirt roads.
The sensation of each wheel was my primary interest, not how fast they are. We all know if you want to go faster you should go aero, and for aero, you need to go carbon. I was focused on comfort, snappiness, stiffness – ride quality, basically.
Picking a favorite
Even though they’re heavier, I liked the aluminum wheels more. Here’s why.
The concept that a softer rim and wheel build can provide some appreciable give, increasing control and comfort, is not new. It’s the guiding principle behind Zipp’s single-wall 3Zero Moto mountain bike wheels, for example, and was long touted as a reason pros stayed on low-profile aluminum tubulars in races like Paris-Roubaix.
I’ve done quite a bit of bouncing back and forth between carbon and aluminum rims of similar depths on a mountain bike. Aluminum wheels generally feel smoother off-road, but a bit less snappy in hard corners when your tires are really biting.
Of course, I’ve ridden plenty of aluminum and carbon wheels on the road, too. It’s harder to make a direct material comparison there, though, as carbon road wheels are almost always far deeper than any aluminum offering, and the differences in ride quality are thus determined primarily by the shape, not the material.
The feeling on gravel was similar to what I’ve previously experienced on mountain bikes. The aluminum EA90 AX set has a bit more flex in every direction. They’re more comfortable and seem to track better over rough surfaces. The sensation is similar to dropping a couple of psi out of the tires – it’s subtle, but noticeable.
In repeated laps on a course with roughly 30% smooth but twisty singletrack, 30% pavement, and 40% dirt road, the EA90 aluminum wheels were routinely a few seconds faster through the twisty singletrack. The segment is roughly five minutes long. The surface on that section is what I fondly call kitty litter over hardpack, and real grip is basically nonexistent. Something about the aluminum wheels was gripping slightly better.
A small part of this difference may come from the minor increase in internal width. One millimeter of additional rim doesn’t change the tire width a ton, but it does add more volume than you might think.
The carbon wheels feel stiffer. This results in a better feel on pavement, particularly when out of the saddle. They snap better when you put a steering input into them. The 150-gram difference in rim weight is noticeable when you flip the bike back and forth, and makes them feel like they’re accelerating faster (the math on this suggest you’re not really going much faster, but it feels better).
The question, then, is which is better for gravel? The stiffer, lighter EC90 option or the more forgiving EA90?
On a mountain bike and a road bike, I find the stiffer feel of carbon results in a better, more controlled ride. A major factor in this, though, is tire grip. Relative to a loose, gravely surface, both road and mountain bike riding tend to have more grip. You’ve got a far bigger tire on a mountain bike, far bigger knobs. Unless conditions have fully detriorated, you can put more cornering force into the wheels without breaking loose. That additional traction feels better matched to a stiffer wheel. The exception is in muddy areas, when something softer can be an advantage.
Same goes for pavement. A road tire on pavement has a huge amount of grip. It’s why you can lean into corners so hard in a crit or a descent. That grip increases the amount of steering force you can put into a wheelset, and means a stiffer wheel will usually feel better, or at least more responsive.
Gravel, in most areas, is a low-grip affair. You’re on undersized tires, have no (or very little) suspension to help the tires track the ground, and the surfaces are often loose. As a result, you can’t push into the wheels as hard when cornering, making a hyper-stiff wheel less important. And the lack of actual suspension means that any give from other components is appreciated.
For the gravel racer interested in going as fast as possible, wheel choice is pretty simple. Find a fat, moderately deep carbon wheel, put a fast tire on it, and go. The aerodynamic advantage available with carbon makes the decision clear, assuming cost isn’t prohibitive.
But for many of us who gravel more recreationally, I struggle to see any real reason to go carbon. The carbon wheels were less comfortable, less forgiving, and felt like they had less grip when I pushed them on loose descents and through singletrack. They felt better on the road, but we’re not talking about road riding.
When you add in the fact that the aluminum wheelset is half the price of the carbon one, the choice gets even easier. That ratio is pretty standard between aluminum and carbon wheels these days, though of course you can spend much, much more on carbon if you want to.
The EC90s are not twice as good. For me, and for the type of riding I do, aluminum is just better.
The AX wheel line: a brief review
Since we have your attention, I have a few thoughts on the AX wheel line in general. Easton has done a good job here.
The carbon fiber EC90 AX wheels were the first to land at CT Colorado Headquarters, and I’ve thrashed them for nearly a year without a single issue. Not a wobble, broken spoke, or hub issue. The 24 mm internal rim width is nice and wide and makes for a great shape with tires in the 35-45 mm range.
That rim seems durable, too. I’ve whacked them in a few square-edge bumps and haven’t cracked them.
The Donnelly Strada USH tires mounted up tubeless to both wheelsets with a floor pump, as did a pair of Goodyear Connectors I was testing earlier in the year.
Easton’s Vault hub has been stress-free thus far, which is my definition of a good hub. The six-degree engagement speed is fine, but I don’t find that matters much in a gravel wheel. They’re not super loud or completely quiet, hitting a nice middle ground.
The pawls engage with a drive ring on the freehub, not the hub shell. This seems like a good idea, as wrecking a drive ring (these things happen off-road sometimes, particularly with poor maintenance) just requires one to purchase a new freehub, not a new hub. I don’t have years and years on these wheels, so I can’t tell you if we’re talking DT Swiss-level durability, but it’s been smooth sailing thus far.