Miscellaneous bits and bobs from the tech world

Test driving the Mammut Smart 2.0; A Review

8/26/2023, 9:51:11 PM

The Mammut Smart Belay Device

Having been climbing more seriously for the last 6 years, my exposure to belay devices has been restricted to that which my local gym allows — that is — the GriGri.

Since its introduction in 1992, the GriGri has taken the climbing world by storm. As an assisted belay device, it offered unparalleled performance and positioned itself as a solid alternative to the king at the time, the ATC.

When I discovered that there were other products on the market that offered similar benefits to the GriGri, I jumped at the chance to test-drive them. My search brought me to two popular contenders, the Black Diamond ATC Pilot, and the Mammut Smart 2.0.

I later purchased a Smart from my local retailer and finally had the opportunity to put it to use today. The following is a brief usage review including some pros, cons, and surprises. There are few reviews of the Smart, online, and most tend to rehash the same marketing points. Hopefully I can provide a unique perspective on the device with my own review.


Simple machine

The Smart is an assisted belay device that uses the geometry of the device itself, in combination with the carabiner, to lock the rope tight when weighted. The engineers at Mammut have clearly done their research as the device locks at the drop of a hat, locks tight, and most importantly, doesn't slip when locked (there is a caveat to this, below).

As opposed to a GriGri with its moving cam and cover plate, the device's solid non-moving construction lends to it a degree of confidence.

Simple to load

Like the GriGri, the Smart comes with a handy drawing of climber and rope along the side of the device, that makes it simple to ensure it is loaded correctly. The device is loaded similarly to an ATC, where a bight of rope is inserted into the top of the device, and locked into place via a carabiner.


Top-rope belaying with the Smart is identical to the GriGri — PBUS: Pull, brake, under, slide. Any climber with familiarity with the GriGri can top rope with the Smart with no additional instruction.

Much easier to swap between paying out and taking in (vs. GriGri)

When lead belaying, you will be switching often between paying out slack and taking in slack.

An excerpt from the GriGri instructional manual; figure 7D — a drawing of a belayer arresting the rope movement by bringing the brake strand down and to the right of the GriGri device

With the GriGri this can be cumbersome as the switch to paying out slack involves hooking your index finger under the lip of the device and using your thumb to defeat the cam. To re-enagage, you let go with your thumb and re-establish the lock at the home position by bringing the brake stand down by your hip. This action means that if you need to go back to paying out more slack quickly, you need to re-establish the cam-defeat.

This action unfortunately introduces a potential bad habit where one may absent-mindedly keep the cam depressed just in case more slack is needed. Many belayers have been in this position where perhaps an armful of slack is paid out, but you are not entirely sure if the climber has enough to clip, so you hedge your bets and keep your thumb on the cam out of fear of shorting your climber.

While doing so can still be safe while the brake stand is held, ones fingers may only be putting in a minimal amount of grip on the rope as you are expecting to pay out slack.

A video still of a belayer using the Mammut Smart — a hand's fingers are wrapped around the brake strand while the thumb is hooked on the nose of the device and the device is pointed downwards

In contrast, with the Smart, you pay out slack by hooking your thumb under the device (at the "nose") while your other fingers are still wrapped around the brake stand, followed by pulling the device up and out. This defeats the lock and allows your guide hand to pay out slack very quickly. Once enough slack is paid out, one can easily hook the nose downwards using the thumb, which easily re-establishes the lock.

More importantly, switching back and forth between paying out and locking is very intuitive as it is as simple as raising the device up and out again. It can be done in less than a second, and allows you to be more accurate with the amount of slack given.

The Smart wins here, hands down.

Lowering is simple and smooth

Caveat: I did not test the recommended way of lowering a climber.

The alternative way of lowering a climber involves grabbing the device with your guide hand (while the brake strand is down and the device is locked) and rotating it backwards, allowing the rope to slip through at a controlled manner.

A common critique of the Smart is that when lowering a climber, the device will go from fully locked to fully open with little middle ground. It takes practice to be able to find the right point. I believe the alternative method resolves this issue altogether. It was very simple to adjust the speed of lowering, and I did not find that the device lowered too slowly or too quickly. Lowering was smoother than a GriGri.

However, it is important to note that this method of lowering a climber is strictly forbidden according to the manual.

Panic? No problem.

The real beauty of this device shows in how it handles in a panic situation. There are two common scenarios where a panic can occur.

  1. If a climber is being lowered and is unexpectedly lowered quicker than expected and the belayer panics.
  2. If a leader is attempting to clip and falls instead.

The first is a common failure mode with the GriGri — in a panic situation, the belayer may pull back harder on the lowering handle causing the climber to fall even faster.

With a Smart — assuming proper belaying position (see note, below) — a panicking belayer will pull the device and brake strand downwards, immediately locking the device.

As for the second, experienced belayers will know to immediately re-establish brake by pulling down on the brake strand. If the cam is defeated (especially in cases where the brake strand is not held), the climber could deck — see video.

With the Smart, once again, the instinctive reaction of the belayer will be to immediately bring the device down, immediately locking the device.

Note: If you lower a climber by rotating the device backwards using your guide hand, then a panic response would be to continue rotating the device back even further, causing the climber to deck, much like the GriGri's failure mode. I believe this is the reason why Mammut does not recommend lowering a climber in this manner.

Cons and Surprises


Some may consider the Smart's locking to be overzealous. As opposed to the GriGri where you can feed rope through by pulling the rope through when the brake strand is unweighted, the Smart will most likely lock up in that scenario.

I consider this a feature, as it simplifies the conditions for rope movement. The rope always moves freely when taking in rope, and the Smart will always lock the other direction. There is no in-between case which introduces possible failure modes.

While my partner and I were preparing to climb, the climber pulled on his end lightly, expecting to be given some slack as the brake strand was unweighted. Imagine his surprise when the Smart automatically locked up!

Carabiner choice

As iterated in advice passed on from other users, your choice of carabiner is important. You need a carabiner with a round stock, as the increased surface area allows the carabiner to pinch the rope tighter. Using a carabiner with an I profile will pinch the rope in such a way that the rope can continue to slowly pay out even when fully weighted.

Mammut sells their own HMS-style carabiner with the Smart as a package, but I did not test theirs.

Carabiner can flip over

I was belaying my partner on top rope when he sat back to evaluate and I noticed that the carabiner had flipped upside down on me. The narrow end was now with the Smart, and the HMS end was with my belay loop. Given how vigourously you pay out or take in slack, the carabiner may flip on you.

Depending on carabiner this may not be an issue, although in my case I was using a Metolius Element II which has a round stock at the round end and an I-profile on the other. See above as to why this may be problematic.

Carabiners with an anti-crossloading bar or clip would solidly resolve this issue. The carabiner packaged with the Smart is one of those.


Because there is less material between the rope, the device, and your hands, the Smart will heat up enough for you to feel through the device. A 15 meter pitch was enough to cause the device to heat up to a noticible degree, although it was only warm to the touch, not hot. Consider it incentive to lower a climber slowly :)

Hopefully these observations give you better context as to how the Smart performs!

A very helpful resource for me was the instructional video put out by Deutscher Alpenverein (DAV)