Problem: Climber is significantly heavier than belayer. This causes a handful of issues: Most commonly the danger arises when the heavier climber falls, causing the lighter belayer to get wrenched into the wall or the first bolt, increasing the chance the belayer will be injured and/or will lose control of the rope. It also creates a dangerous possibility where the lead climber can experience a ground fall if the light belayer is rocketed too far off the ground.

Most solutions to this problem attempt to make the belayer “heavier.” In gyms, it’s common to use sandbags or other types of anchors to weigh the belayer down to ensure they stay on the ground. The Edelrid OHM tackles this problem from the other side, by reducing the force the heavy lead climber exerts on the belayer.

Engineers in particular will enjoy the wordplay with the name, as Ohm (Ω) is a unit of measurement for resistance.

TL;DR The OHM is best for use in the gym, climbs with limited natural friction, climbs where decking is a greater possibility, or when you want limit light belayer collisions during a fall.

It will be extra helpful for new climbers with big partner weight differences, as the added friction will allow greater control while catching falls and while lowering.

OHM Benefits

The OHM is not a belay device by itself. It is designed to be an assisted-braking, friction-adding device that is clipped to the first bolt. During a fall the OHM increases rope friction so the lighter belayer can more easily hold the heavier climber without being pulled off the ground.

The OHM adds additional friction even when only the first bolt is clipped, reducing the distance of a fall which reduced the likelihood of decking.

It is particularly helpful in reducing forces in the gym, as the routes are much straighter and there is less friction in the system. The more vertical the route, the more benefits the OHM will add.

When I belay heavier climbers in vertical climbs on rock with hardly any natural friction by the rope, I prefer the Ohm.

-Angy Eiter, 4x World Champion Climber

That said, the OHM does not add friction during normal climbing. It’s only activated when the climber weights the rope, either during a fall or when lowering. The added friction during lowering enables a safer, more controlled descent.

Psychologically, the OHM can also reduce the fear of hurting a light belayer during a fall, or safety concerns around particularly on low cruxes.

Mike Rougeux, the Climbing Program Director for the Bend Endurance Academy says that, “As a coach, having access to an OHM with our competitive youth climbing team gives me a lot more options with how I structure our sessions and who I pair up as partners. The first bolt/draw in a lot of commercial gyms can be pretty low, and when you have a larger lead climber paired with a smaller belayer you can run the risk of the belayer being pulled into the first bolt.  Introducing the OHM into the system allows me to have more options of who I pair up to climb together.”

Edelrid Ohm - both sides

For Heavy Climbers and Light Belayers

Often touted as most beneficial for climbing couples, the Edelrid OHM will surely be a relationship saver for heavy projectors. But the OHM is only helpful if the climber is heavier and the belayer is lighter.

It is not recommended to use the OHM with a lighter lead climber and heavier belayer because the OHM will add friction into the system (as designed) and it will make the fall much less dynamic.

Ideally the belayer’s minimum weight is 40 kg / 88 pounds. And ideally the maximum weight difference is 40 kg / 88 pounds as well. So, if the belayer weighs less than this, the OHM alone may not solve the issue.

Edelrid has put out a great demonstrational video:

Note: Although this official video shows the OHM attached to a normal quickdraw, it will not be sold this way. It will only be available pre-attached to a quicklink on a quickdraw.

When I first watched a video of the Ohm being used I thought it was a bit gimmicky and wasn’t sure if the extra steps of setting it up would be worth the added benefit for the belayer… The first lead fall I caught while using the OHM I was sold.  

-Mike Rougeux, Climbing Program Director

Weight Reference

The newest educational standard from the German Alpine Club (Deutsche Alpenverein aka DAV) suggests there should be no more than a 10kg (22 pound) difference between the belayer and climber. This number has been reducing over the years as the DAV continues to study the belay habits of climbers to ensure a safe experience.

For what it’s worth, I weigh less than 120 pounds. In the last 7 years, my main climbing partner, Andreas, has weighed between 160 and 175. This is a +35-48% difference – which is higher than even the old European standards recommend. I can actually tell if he’s gained or lost weight in how it feels to belay him. When he’s on the heavier side of that spectrum, even during a smooth lower, I can be lifted off the ground. Whenever he falls, my feet come off the ground. Because of this, I am really interested in testing an OHM, particularly to belay Andreas while he’s projecting a route.

The OHM is out now!


How to Use

These are basic instructions and are subject to change. Please read the OHM manual for proper use.

The OHM should be used on the first bolt to be the most effective in ensuring the lead climber won’t deck.

The easiest way to use the OHM is after the lead climber ties into the rope:

  • Open the OHM and insert the rope
  • Close the device and hang it as the first quickdraw on the harness
  • Start climbing and clip the OHM’s quickdraw into the first bolt

Edelrid Ohm loading

You could also stick clip the OHM quickdraw with the rope installed on the first draw.

The OHM can be pre-hung without the rope installed as well. When you reach the OHM, open it via the lever, insert the rope, and close the device.

Alternatively, you could hang the OHM in the open position to save time clipping.Edelrid Ohm - Lever that opens

The OHM is not bi-directional. It would be wise to add checking the OHM orientation to your partner check. The OHM has engravings on one side, and on the other side a sticker, both pointing to the climber side of the rope.

Edelrid Ohm Safety Labels

In the gym, if there are already pre-hung quickdraws, clip the OHM draw into the top quicklink/carabiner of the gym draw.

Clipping Edelrid Ohm in Gym

Once the OHM is engaged (from weighting the rope), it can be disengaged by the belayer with a simple shake of the rope. The OHM will return to its standard position with no friction added to the system.

Threading the rope in the wrong direction is the only misuse possibility. Fortunately, in this case there is literally no impact. The OHM will not do anything in this case. The only downside is that if you were expecting the extra friction, you could easily be caught off-guard.

How the OHM Works

During normal belaying there is no added friction from the OHM. You’ll see this when the OHM is closed around the rope and can move the line seamlessly through the device. This device does not impair clipping and only activates in the event of a fall.

When a fall occurs, the OHM is pulled upwards, changing its orientation relative to the rope and a camming unit adds friction, which reduces the force transferred to the belayer. It took several years of research to create the proper camming mechanism.

Edelrid Ohm Cam

Edelrid has done extensive testing to ensure the OHM does not degrade/damage the rope in ideal uses (falls from all bolts other than the first bolt).

The worst case scenario (using the OHM or not) is if the climber falls on the first bolt. With an OHM, this is where the rope would engage the cam most heavily. In laboratory settings (using the least dynamic belay situations), with a heavy “climber” and really thin single ropes, you could see some sheath damage from a hard fall on the first bolt. With ropes above 9.5 mm in diameter, there is no noticeable sheath damage in this scenario.

Device Details

The OHM is stainless steel inside to ensure longevity and plastic on the outside to reduce weight.

Edelrid Ohm - open

It will be 360 grams. As Canmore guide Scott McKay says, “When I hand the device to most people they immediately think that it’s a bit heavy for its size. Not a big deal for gym use and after all you’re only going to carry it up to the first bolt!”

It is meant for both indoor and outdoor sport climbing use. It is not recommended for trad climbing because the OHM will pull up on the gear, which is most likely the opposite direction of how the gear was placed. Also, the placement connected to the OHM will be loaded with a higher force than usual, due to the friction caused by the engaging OHM. The endless hypothetical situations make recommending the OHM for trad use impossible.

The range of the OHM is made for rope diameters 8.6 – 11 mm, which covers the full range of single ropes typically used for lead climbing. Scott McKay, whose tests included the upper range, did note that if you’re using the OHM with a 10.5mm fuzz monster of a rope you can expect it to be a bit grabby during normal quick draw clipping.

Edelrid Ohm Full quicklink

The OHM will not be sold as a single device. Instead, it will be sold as a complete quickdraw with the OHM attached with a quicklink. The quicklink is tightened to the correct torque at the factory and it is not intended to be opened.

The length of the quickdraw does influence the function of the device, so it is advised to only keep it on the 10cm quickdraw that it comes with (the longer the dogbone, the longer it would take for the OHM to activate and conversely, the shorter the dogbone, the quicker the OHM will engage).

Belaying Nuances

Belaying will continue as standard. Normally, light climbers do not stand super far away from the wall, so this will be no different (standing too far away from the wall will increase the OHM engagement angle and may end up short-roping the climber). It is ideal that the belayer stand about a meter away from the wall to create a slight angle from the rope to the OHM, to ensure it will catch (standing against the wall will create virtually no angle and the cam will take longer to engage, reducing the OHM’s helpfulness).

Since the lead climber will start climbing with the OHM rigged on their harness, it will help to give some additional thought as to which side the belayer should stand to avoid having the rope getting caught behind the climber.

Once the OHM is engaged, it just takes a very slight wiggle of the rope to release the OHM’s friction. This is most easily done by the belayer, although it could also be done by the climber in most situations.

Scott McKay added this final word of belaying caution: In some circumstances it will be difficult for the belayer to let the rope run in order to allow the climber to fall past roofs, ledges, etc.

Climbing Nuances

Depending on the rope set-up (rope diameter, position on the route, angle of the wall, etc) – the lead climber could technically pull slack so quickly that it would engage the OHM. In this case, the climber would stop pulling slack and wiggle the rope which would allow the OHM to disengage, and then pull the slack rope again. This action would be very similar to a seatbelt engaging/disengaging.

When Juan Rodriquez from AntiGravity Equipment did some testing with the OHM he noticed that his belayer’s (previously excellent and dynamic) skills felt decreased with the OHM, as the added friction meant the fall was a little harder than normal. That said, Juan is still excited to use the OHM in possible ground-fall situations.

The OHM will not be the best choice for routes that are significantly meandering or if they’re greatly overhanging between the first and second bolt. Both of these situations will move the rope closer to the camming unit inside the OHM, and this would cause the rope to enter the camming position sooner than normal. The OHM would still decrease the chance of a ground fall, or the belayer coming off the ground, but it would also increase the short-roping possibility for the lead climber.

The biggest difference in climbing with an OHM, is that, after the leader has climbed the route they’ll want to clean the OHM on the way down, which takes some getting used to. Mike Rougeux, the Climbing Program Director at Bend Endurance Academy noted that, “On steeper terrain, you’ll need to climb back up to the first bolt to remove the OHM since the climber will be so far out at the base of the wall [during the rappel]. If the opening moves are at the climbers limit and/or the first clipping stance isn’t great or the climber tries clipping off a poor stance it can seem a bit frantic.” It is unlikely this will be a problem while gym climbing as most gym settings avoid adding a crux before the first bolt.

Mike offered some additional advice: When using the OHM it’s also a big help to think about your first clip and the stance you’ll be in so that you can position the OHM pre-rigged on the most convenient side of your harness.

Read First Hand Reviews from OHM Users


The most helpful time to use the OHM will be when the lead climber is significantly heavier than the belayer and the bolted climb is mostly straight (not meandering or steeply overhung between the first and second bolts). The climbing gym is where the OHM will excel the most and will inevitably prevent ground falls and belayer/climber collisions. The OHM will be particularly helpful for new climbers as it’ll add additional friction to help enable controlled belaying and lowering experience.

When we interviewed Shad Burnham, VP of Sales at The Front Climbing Club, he rounded up his expectations and experiences of the OHM as such: At first I was like, ‘great, another device for a problem that doesn’t exist’ … but then as I used it and started to realize the range of uses/situations it could help in, I realized how valuable the OHM is. It’s easily the most important innovation in ground fall protection since the Grigri. I don’t say that lightly either. I’ve been a climbing buyer for almost 10 years. In that time, there’s been a lot of gimmicky devices introduced to the market that may or may not have stuck around. The OHM does not fit that bill. It will save lives.”


The OHM will debut as the only device of it’s kind and debuts at $129.95.

October 2016: Climbing gyms in North America will get the Ohm (for gym use only, not sold at retail).

December 9, 2016: will start selling the Ohm (it’s out now!).

January 2017: Wider Ohm distribution in North America, including REI.

Europe will see OHM distribution starting in November and early December 2016.

Alison Dennis

Alison Dennis

Alison (she/her) runs WeighMyRack from her 17' travel trailer. She is currently touring the US and would love if you contacted her to meet up to talk about climbing, climbing gear, or if you have any fun and/or ridiculous adventure in mind.

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