Honestly, most wobbly legs on urban outdoor furniture come down to loose hardware, uneven ground, or worn feet. I’d start by emptying the piece and turning it on its side on a soft blanket so you don’t scratch the finish or your balcony tiles.
First, check every bolt, screw, and bracket. Tighten them in a star pattern, like you would a car wheel, and don’t crank them down so hard that you strip the threads. If a bolt keeps loosening, remove it, add a split washer or a little blue threadlocker, and tighten it again. For wood furniture, a stripped screw hole can be fixed by filling it with wood glue and a few toothpicks or a dowel, then re-driving the screw.
If the frame is tight but the leg still rocks, the problem is often the floor. Balconies, patios, and small urban courtyards are rarely perfectly level. Get a helper to press down on the high legs while you slide a rubber, composite, or plastic shim under the short leg. Trim the shim so it barely sticks out. Avoid cardboard outdoors—it turns to mush. If your furniture has adjustable feet, twist those first before adding shims.
Next, look at the bottom of the leg. Worn glides, caps, or feet are a common cause of wobble. Pop them off and replace them with outdoor-rated adjustable glides or rubber caps. If the leg itself is bent, cracked, or rotting, replacing the leg or the whole piece may be smarter than fighting it.
For metal furniture, check the welded joints. A small crack can make the leg flex. If you can weld or know someone who can, great. Otherwise, a bolt-on L-bracket or corner brace can stabilize it. For wicker or resin, make sure the leg insert hasn’t pulled loose; epoxy it back in and let it cure fully.
Once it’s stable, set it on the ground, sit gently, and then add weight slowly. If it still wobbles, repeat the shim check. To prevent it from coming back, tighten the hardware at the start of every outdoor season, keep the furniture on a level surface, and lift rather than drag it across concrete or tile. That usually turns an annoying wobble into a solid, safe piece again.