Design
In terms of technical features, the 0.4, 0.5, and 0.75 X4s have a head design that should be familiar to anyone who’s used C4s—there’s a dual axle with external springs situated in between each pair of lobes. Because space is limited on the heads of the smaller three sizes, these have internal springs (so that the lobes sit flush against one another) and an axle configuration that Black Diamond calls “Stacked Axle Technology.”
The dual axle system, previously made famous by Camalots, is popular since it offsets the lobes of the cam and gives the device a greater usable range. The stacked axle technology is intended to provide the same improved range relative to a single axle in a package compact enough to fit on the head of a microcam. Though meant to stand in for the double axle system of the large sizes, I wouldn’t place these cams passively and feel good about it.
The idea here is that the column on which the cams are fit is slightly offset from the central axle, allowing for two axles of rotation without having the two axles sit entirely apart from one another (as is the case with the C4s, larger X4s, DMM Dragons, etc.). Black Diamond claims this gives them more expansion range. I definitely felt like the smaller X4s were easy to work with, and didn’t have any of the finicky behavior occasionally found in small cams, such as the smallest Helium Friends.
Having said that, I don’t think the expansion range on the stacked axle X4s is all that different from the expansion range of the Master Cam or Alien—for example, the 0.1 X4, 00 grey Master Cam, and black Fixe Alien all cover essentially the same range. The X4 line does, however, blow the C3 range out of the water in this regard—three X4s cover nearly the same range as five C3s.
As for the internal springs on the smaller sizes, I think the extra metal-rock contact afforded by having the lobes in each pair flush with each other is great. They hold very firmly thanks in part to the amount of surface area contact (relative to the small size of the head).
If there’s a downside to the internal springs, it’s that they’re harder to clean. Take special care to keep these smaller sizes out of the dirt. They haven’t gummed up too bad on me over the course of one season, but I was careful to keep them off the bare ground. I have a feeling that one accidental swim in the fine dust in Indian Creek might be challenging (at least to your patience) to undo.
Strength Ratings
The strength ratings for the 0.1, 0.2, and 0.3 X4s measure 5kN, 6kN, and 8kN respectively, ratings that are comparable to those of the Master Cam line, and lower than those of the Fixe Aliens.
(How much this matters varies from climber to climber. Cams rated around 5kN or so are really only rated for aid climbing—they’re not meant to catch huge whippers. Granted, people do take this big falls and the cams often hold, but the point is that as the components get smaller and smaller so does the quantity of metal holding it all together, and there’s a reasonable limit to how much you can load these tiny things.)
It is worth noting that the three largest X4 sizes—the 0.4, 0.5, and 0.75—are rated to 9kN whereas their counterparts in the C4 line are rated to 10kN, 12kN, and 14kN respectively. Are you likely to exceed 9kN for a single cam placement? Hopefully not. But the 5kN difference between the 0.75 X4 and the 0.75 C4 is significant, and worth pointing out in the interest of keeping an eye on the limits of our gear.
On the Rock
As far as real-world holding power and performance, the X4s are as good, if not better, than any other small cam I’ve used. I carried the four cams with me all season, and I got used to using them very quickly.
In general, I think the flexible wire stem concept (which precedes the X4s, of course) is ideal for small cams, and the X4s are maybe the best realization of that concept thus far. They’re extremely secure and make it easy to get a lot of metal touching the rock—thereby improving some marginal placements—and they’ve got a low enough profile to find purchase in pin scars.
The slim profile is great, and not just for pin scars. I got some good use out of the X4s at Vedauwoo, particularly on the climb Deep Throat on the Nautilus. The short pitch starts out as an off-width in an acute corner that overhangs and thins down to awkward, flaring thin hands. Thankfully, good stemming on either side of the corner keep the climb to a very manageable 5.10a (though definitely not a give-away 10a, even for Vedauwoo).
On the other hand, the gear on the top half of the pitch is all there, but it’s a bit odd since the crack flares out and downward and demands that you grapple with some large crystals and inclusions in the granite.
I was able to get a solid 0.75 X4 in right before the crux bulge at the top only because the head was thin enough to fit in between the features that existed in the crack. On the way down, I tried playing around with a 0.75 C4 in the same place and had a much harder time getting the placement to sit securely. Point goes to the X4s.
Bottom Line
The X4s are currently my all-around favorite small cam. Setting aside minor gripes about the short stems in smaller sizes and a slightly wonky stem, they’re a fantastic whole package.
They take up less room on your harness and marry a lot of the positive aspects of Master Cams and Aliens (which are fantastic in their own rights) to a sleek, slim profile and familiar camalot sizes.
You’ve written:
On the other hand, the 0.5 and 0.75 X4s (the largest two of the six), are dramatically thinner than comparably sized C4s, Helium Friends, or Master Cams. In fact, the four cam lobes on the 0.5 and 0.75 X4 sit in the same space as just three of the four lobes found on the same size Black Diamond C4.
Do you think that this is a disadvantage? I meat that the more narrow head is the less placement is stable? I think that with 0.75 with reduced head width (between BD C4 and X4) you can put it in more tricky placement. But, well, stability…
And the second thing about X4. Sometimes I find it too flexible – a cable is bending during closing lobes. Have you such issue? But the ones that I’ve used really needed greasing.
Regarding the stability, I haven’t noticed that to be a concern as a function of the head width. In fact, when the stem acts to rotate the cam, the wider head will have a longer “lever” in terms of the basic mechanics involved and significan’t off-set the stability that you might get from the head having a wide “stance.” Additionally, the soft stems (relative to Black Diamond C4s, Helium friends, etc.) help isolate the lobes from the movement of the rope in the same way, but to a lesser extent, as a sling. In the real world, I haven’t seen any actionable difference between stability in the X4s and the Black Diamond C4s in the same size, and any slim difference is easily overcome by the ability to work with thinner (or slightly flaring) placements.
As for the softness of the stem, this is definitely the type of issue that colors peoples experience with one cam or another. While truly rigid stems are obviously impractical, a really heavy cam (say, off fingers or thin hands sizes) on a super soft stem can be irksome. Pairing excessively stiff springs with a soft stem can be equally problematic. As for the X4s, I use the 0.75 regularly without much trouble from the soft stem. In fact, as far as the stiffness of the stems go, I generally have an easier time with the 0.75 X4 than with the comparably sized black Metolius Mastercam.
This is definitely wading into personal preference, though, and I do know other climbers who don’t like to use those types of single stem cams (Mastercams, X4s, Aliens, etc.) in sizes any larger than perfect fingers. In my opinion, the real issue with the stem on the X4s is the needlessly short stem on the two smallest sizes. They threaten to get stuck with some regularity despite otherwise being excellent micro cams.