Review: Dynafit’s Mercury (& Vulcan)

Aside from fit, there is precious little to complain about with Dynafit’s TLT boot line. All utilize Dynafit’s patented Ultra Lock System that integrates the mode switch with the cuff buckle for shifting gears to uphill or downhill with a single move. That alone warrants a closer look for my turning earning friends.

As the thinking goes, if it’s good for the up, it’s bad for the down and the holy grail of every backcountry boot made is to find the right balance of each with the widest span possible. Inevitably a compromise is made in one direction or the other, but Dynafit’s Mercury (or Vulcan if you insist) has arguably the widest range available in an alpine boot.


 
Touring ROM

The TLT5 cuff mechanism automatically takes the prize for the greatest rear cuff ROM of any alpine boot on the market. A solid 29°+ to the rear, allowing for a longer stride and with better glide. This is one of the few boots where the limit of what the boot can flex to is about as far as you would want too, making it a very soft limit. With almost any other boot, you notice the limit. The better ones feel soft because they flex so far, while the ROM for sidecountry boots is like hitting a wall, and quickly at that.

Where’s the beef?

While in-bounds alpine and sidecountry boots may still ski better than a Mercury or Vulcan, it won’t be because they are stiffer, but because they have a progressive flex that becomes even stiffer the further you flex it. Alas, no one has figured out how to create a lightweight boot with a stiff flex and a progressive feel, but Dynafit actually comes pretty close with their removable tongue. They definitely equal the stiffness of race caliber boots, especially with the Vulcan. For most folks, the Mercury is plenty stiff enough.

In combat conditions, stiff boots are your friend — in powder they limit the range of sensations. While the normal configuration is stiff enough with the Mercury, ridiculously stiff with the Vulcan, both can be moderated to allow for a progressive flex by removing the shell tongue. In either case, the reduction in flex resistance will be a welcome relief in soft snow conditions, some of us might even say, all conditions. 😉

That rigidity derives from using a Grilamid lower shell which is 5% stiffer than Pebax, yet lighter. Combined with skeletal ribs for strength the shell can shed more material, yielding a boot weighing les than 3½ pounds per foot (1.51 kg). Yet it has the ability to drive your edges with solid bite in the throat of a couloir loaded with hard, no-fall zone snow. While stiff, that stiffness is not a progressive sensation, but a step function that provides max resistance from the get go. The more mass you have to drive with, the more the cuff will yield, but it ain’t easy. If you remove the tongue, some of the progressive feel of a classic alpine boot with an overlap tongue returns.

The main difference between the Mercury and Vulcan is the material in the cuff. For the Mercury, fiberglass reinforces a Grilamid cuff which, as I keep saying, is plenty stiff enough. For those who prefer ridiculously stiff, the Vulcan uses a carbon fiber reinforced Grilamid cuff. Oofff! Better for you perhaps, but not this kid. I skied a pair for a day and ended up taking the tongue out to soften the Vulcan’s up to a more acceptable level and they still felt stiff.

You can chose between a 15° or 18° forward lean by changing the position of the locking hole on the internal achilles spine, but you can’t easily switch between the two positions. Pick one and like it.

Even if you don’t want to soften the flex of the boot for downhill, on a long climb it may be worth it to put the tongues in your pack, further improving ankle flexibility for more efficient climbing.

Them Details
Dynafit’s TLT5 series boots all come with some pretty nice finishing details. The power buckle on the cuff allowing race caliber touring motion is reason enough to consider these boots. But there’s more to these boots than just that. Consider the buckles, which are micro adjustable, and lock into position on the ladder so you can flip the buckle open without it flopping around and having to reposition it.

The power strap uses the classic hook n’ loop adjustment system, but adds a tab of material at the end so the strap can’t fall out without taking time to wedge the extra width through. It makes it a pain to thread in when you first cinch your strap up, but when you want to loosen it you just rip the Velcro apart and it won’t slide open and flop around. IOW, you don’t need to adjust it to a looser position, you just open, let it go and keep moving, rando style.

The Fit

As I said right up front, about the only thing you might not like about the Mercury, or Vulcan is the fit. If you have a wide foot and an high instep, you’ll need an over sized boot to make these comfortable. However, for everyone else, you shouldn’t have much problem making these fit. Just remember that with a heat moldable liner if they feel too snug before molding, within reason, that’s a good sign. For most folks though all it takes to relax that pressure is to heat mold the liners.

Dynafit did a good job of working with Intution to come up with a liner that can accommodate a descent range of foot volumes without compromising warmth or performance. I’ve seen D width feet smile with the feel of a Mercury after heat molding, just like some B sized feet do without.

There are multiple densities of foam, to enchance the driving power from your lower leg, and comfort of your toes. A wedge of softer foam is cut into the Achilles zone, to allow for easy rear flexibility so the liner doesn’t steal any motion that the cuff hasn’t denied.

Plus there are other details you want, like a rubber sole for walking around camp, and laces for the same. The upper tongue has a patch of reinforcement, again for more power transfer.

Bottom Line
It’s an old adage, but as they say, if the shoe fits, wear it. If these boots fit your feet, except for the fact they don’t tele for squat, I don’t think you’ll be dissatisfied with their performance, in or out of bounds, up or downhill. If you insist on super stiff, try the Vulcans. If you’re still a charger but don’t need that much brawn, stick your feet in the Mercury.

Dynafit
Mercury
MSRP: $800
Weight/boot (mondo 26.5): 3 lbs., 5¼ oz. (1510 g)
Size range: 22.5 — 31.5 (mondo)

Vulcan
MSRP: $999
Weight/boot: (mondo 26.5)
Size range: 22.5 — 31.5 (mondo)

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