SUCK DOWN WINCHES: WHAT THEY DO AND WHY YOU PROBABLY SHOULD NOT FIT ONE
13 min · Free lesson · written from fifteen years in the terrain
After this lesson you understand what a suck down winch actually does on extreme terrain, why the loads involved make it a different hazard to a recovery winch, and why the technique it teaches is worth more to a touring driver than the hardware.
The Technique
- Start with the name, because it describes the job exactly. A recovery winch pulls the vehicle forward toward an anchor in front of it. A suck down winch pulls the vehicle DOWN, toward the ground or toward its own axle, to keep a tyre loaded when the terrain is trying to unload it.
- Where it earns its place. On a steep ledge or a near vertical climb the nose wants to lift and the front tyres go light, and once they are light they stop steering and stop driving. On severe off camber the uphill wheels unload the same way and the truck starts to think about lying down. A suck down winch fights both by adding artificial weight exactly where the terrain has taken it away.
- It is a competition tool. It comes out of comp truck and Ultra4 style rock racing, where a driver is trying to clear an obstacle in one attempt on a course somebody built to be barely possible. That is a completely different problem to getting a loaded touring vehicle across Cape York with the family in it.
- The loads are the whole story. A recovery winch pulls against the mass of the vehicle and the resistance of the ground, and the line runs away from you. A suck down winch pulls the chassis against a fixed anchor with the line running under the vehicle and back toward it, so a failure sends energy toward the truck and toward anybody standing near it. Same rope, different geometry, different consequence.
- Which is why the mounting is the real engineering job, not the winch. It has to go into chassis rail or a properly designed and welded structure that spreads the load into the frame. Bolted into sheet metal, a bull bar tab or a bumper mount, it will eventually tear out, and it will do it under maximum tension.
- Synthetic line rather than steel, and a damper on it. Synthetic stores far less energy than wire rope and does not whip the same way when it lets go. Neither makes it safe, both make a bad day less bad. The damper goes on any line under load, every time, without a discussion about it.
- Nobody stands in the line's path, and on a suck down setup the path includes under and beside the vehicle rather than only out in front. Work out where the energy goes before you tension anything, and move people out of that cone.
- It changes how the vehicle behaves in ways that are not obvious. A truck held down at one corner does not articulate normally, cannot shed load through the suspension, and cannot be driven off an obstacle the way an unrestrained one can. If something goes wrong you are now pinned to the terrain by your own equipment, which is a genuinely difficult situation to unwind.
- The honest verdict for a touring vehicle. Weight, complexity, another failure point, another thing to maintain, and a set of loads your chassis was not designed around. On a trip where the goal is arriving rather than clearing an obstacle, the answer is almost always to pick a different line, air down, take a run at it properly, or go around. See The Build You Do Not Need for the general version of this argument.
- What is worth stealing from it. The thinking underneath a suck down winch is that traction is about weight on a tyre, and weight on a tyre is something you can influence. You do the same thing for free with line choice, with where passengers sit, with how the load is packed, with tyre pressure, and with the run up you take. Understanding why the comp truck fits one makes you better at not needing one.
Common Mistakes
Treating it as a second recovery winch. Fix: it is a hold down, and the line geometry points the failure at the vehicle rather than away from it. Rig it as its own thing with its own hazard cone.
- Mounting to a bumper, a bar tab or panel steel. Fix: chassis or a purpose built structure that spreads load into the frame, or do not fit it at all.
- Standing anywhere near the loaded line because it is short and low. Fix: short and low does not mean low energy. Clear the area and damper the line.
- Fitting one to solve a problem that is really line choice or tyre pressure. Fix: work the free options first, because they are also the ones that work when the winch does not.
- Assuming articulation and recovery behave normally while it is tensioned. Fix: plan how you get out of the situation before you get into it, including how the line comes off under load.
The Drill
Do this without a suck down winch fitted, because the skill is the point. Find a safe off camber slope in an open area with a spotter. Work out, before you drive, which wheel is going to unload and why. Then change one thing at a time, the line you take, tyre pressure, where the heavy gear sits, where a passenger sits, and see how far you can move the loading on that wheel with no hardware at all. The standard is being able to say which corner is light and what you did about it.
A tensioned line running under and back toward the vehicle puts the failure energy where the people are. Synthetic line, a damper, nobody in the path, and a mounting structure into the chassis. If you cannot say with confidence what the mount is welded to and what it spreads load into, do not tension it. This is competition equipment on courses with recovery crews standing by, and none of that exists on a remote track.
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