My cams are rusted. Are they still good?
Rust is caused by the surface oxidization of iron or steel in the presence of moisture and oxygen. Rust is corrosion, and pits or eats away the metal. Since rust takes up more space than the metal it has eaten, it can bind up moving parts such as your cams. Likely, the rust is associated with the camming unit’s axle, which will be steel. The cams themselves are aluminum, which doesn’t rust.
There are many ways to remove rust, including using a wire brush, but the corrosion is on an interior component, which you can’t reach. If you fear that the rust may have compromised the unit’s strength, toss it and replace it.
Best is to avoid rust in the first place. When your cams get wet, air them out to dry, then lubricate them a graphite spray or Tri-Flow. Avoid oily lubricants such as WD-40; the oil will attract dirt. In a real pinch, when you are on a climb and a cam seizes up, you can lubricate the unit with spit.
Do keep your camming units in good order, operating smoothly. Cams that are “sticky” aren’t just hard to use, they can be dangerous. A carefully tensioned spring presses cams into a placement. When the cams don’t work smoothly, they might not have enough spring tension to grip the rock adequately.
Is it better to go expensive, and buy quality cams that will last, or buy cheap and sacrifice quality?
Inexpensive units can work perfectly well, but usually they cost less because the Research and Development and quality control aren’t there. R/D and quality control are expensive and jack up retail price. Since both aspects are invisible to the consumer, a manufacturer can skimp or leave them out entirely and the consumer is no wiser. Before you buy a cam, read its hang tag to determine if it is CE/UIAA approved, if it was batch tested or individually tested, and if its manufacturing conforms to ISO quality-control standards. Put a check in the minus column for every item the cam lacks.
In the store, you may or may not, besides the price tag, notice a difference between the cheap and expensive cams. These days, all cams come with sewn slings, are color-coded, etc. But in the field, you many notice big differences between triggering, cam action and range. In most cases, the top-end cams are easier to trigger, feel smoother and have greater camming ranges because the manufacturer put a ton of time, thought and money into the product.
Do cam teeth do anything?
Maybe. Manufacturers add them because, while few of us can grasp the real magic that locks a cam into place (the “constant angle”), we think that teeth help. But it’s mostly marketing, as cams without teeth would hold just the same.
When Ray Jardine rolled out the first commercial camming unit, the Friend, in the mid 1970s, he tried to be practical by making smooth-faced cams. But the first climbers to see the units scoffed and said they’d never hold. Only after Jardine added teeth did climbers begin to trust them.
Some people claim that teeth help the cams bite into grimy placements. This makes sense, but there’s no data to prove it. Still, since confidence breeds safety, the psychological advantage afforded by cam teeth justifies their existence.
Are “offset cams,” or units with different-size cam lobes on each side of the axle, really useful?
Offset cams are for flared placements such as the pin scars on El Cap’s Salathe. In flares, these little units are miracle makers, holding fast where almost nothing else will. For regular old free climbing, however, they won’t be as versatile as regular cams. In parallel cracks, you’ll never get both sets of the offset unit’s cam lobes to rest on their sweet spots, the mid-expansion points. When the larger cams are at mid-range, for example, the smaller cams might be close to tipped out. And when the smaller cams are at mid-range, the larger cams will be crammed way down, possibly overcammed to the point where removal will be problematic. Together, both problems limit the offset’s effective camming range.