I've never had any of the leg locks on my old (from the '60s) aluminum Gitzos freeze up, but the rubber grips on all of them have disintegrated over time and become useless. If you ever experience this, just use a sharp knife, e.g. an Exacto, to remove the grips and then apply some 3/4-inch wide friction tape (Lowes has this) to wind several wraps around the lock rings (to desired thickness). It works great. I've done this to ALL my Gitzos, all lock rings, all sizes up to 1-5/8-inch diameter. An extra benefit: tape acts as a good insulator and is more comfortable with bare hands in freezing temperatures.