Resistance is not futile! Edelrid OHM assisted-braking resistor review

It seems that the design of a belay device often gets re-imagined and polished these days, but since the days of drilling out looted railway nuts and shoving rope through a metal ring there isn’t an awful lot that can be done to that design.

Variations on how the ring or plate itself might move to help pinch the rope against the carabiner are now common (Wild Country SRC, Climbing Technology Click-up, Mammut Smart, Edelrid Megajul etc), and we are now seeing various players come to market with their version of an assisted braking device (Trango Vergo, Camp Matik, Petzl Grigri+, Wild Country Revo etc).

Edelrid have now progressed beyond tinkering with the design of the belay device and have designed a product to help counter one of the main issues facing climbing partners on indoor and sport lead climbs; weight difference – specifically the imbalance of forces generated when a heavier climber falls onto one end of the rope.

The Ohm is an “assisted braking resistor” that is put on the rope in the system as the first runner on a route.  You climb and belay as normal, with apparently no noticeable difference – until the climber falls off or commits to the rope.  At this point, the first runner is pulled upwards.  This changes the orientation of the device and applies increased friction to the rope running through the device.

The belayer therefore requires less braking force in their control hand as the system is adding resistance.  The Ohm doesn’t stop the rope; “it progressively brakes the speed it runs through”.  The belayer can still belay dynamically, but the Ohm helps reduce the sudden force applied to the belayer in the event of a heavy leader fall.  The videos on Edelrid’s website and social media show a very light belayer taking some impressive dynamic belays that would be (at least) eye-opening to some less attentive and skilled belayers.

When they put the Ohm in the system and re-create the fall, she still has to belay dynamically (ie. She would still spill her coffee), but the impact and force she has to manage are significantly less violent.

The Europeans have done maths and tell you that a climber should not weigh above 30% more than their belayer.  We’d say this is good guideline, and that there are many factors to consider when sizing up the physical weight of your partnership: skill and ability of belayer, belay device, rope, friction in the system etc.  We’ve seen a pulley used at the top of a bottom-rope system, and watched an experienced adult belayer be yanked part way up the crag by a 15 year old female climber.  He was quite surprised to find himself that far up the crag!  Whilst the Ohm wouldn’t have helped there, the lack of friction clearly played a significant part.

Adding friction to the system on indoor or sport leads can help light people hold the fall of a heavier person, just remember: there is no substitute for proper belaying and understanding of the forces involved and how to handle them. Edelrid have made a device to help you handle those forces with a little more control.

See more at the Edelrid website.

We’ve got hold of one of the Edelrid OHM and will be bringing it to our Climbing Wall Lead Award Training courses and staff CPD days this year. Book yours at or contact us at to discuss staff CPD refresher training workshop days.


Post by Jenny Haygarth

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