Cams versus Offset Cams

I have been working on building up a trad rack for a bit now and, being fairly new to the trad world, was wondering what the difference is between cams and offset cams? Are there different applications or is it just a name thing? Thanks for your input

Offset cams have different sized lobes on one side versus the other; i.e.. usually 2 lobes smaller than the other 2. They are mostly used in flaring type cracks, i.e. the outside of the crack is wider than the inside. I have found them most useful in pin scars and in the eyebrow formation that we have here in North Carolina (see pictures of Looking Glass for examples). Overall, I have found them to be of limited use compared to normal cams in the places that I tend to climb. I have found them nice to supplement regular cams, especially when aid climbing. Unless you climb somewhere fairly unusual, you are probably better off having a set of regular cams first.

In a good cam placement, you want both lobes to be equally retracted, i.e you don't want one side of the cam to be more or less cammed than the other side. Regular cams are meant to be placed in parallel cracks in order to keep the all the lobes equally retracted. Offset cams have one set of lobes that are smaller than the other set, making them able to hold in non-parallel cracks (aka flaring cracks) while maintaining equal retraction of all the lobes. Man - I need a picture.

Basically, you need offset cams if your climbing in a place with a lot of flaring pin scars (Yosemite). Sometimes offsets are the only cam that provides a good placement. Outside of pin scars they are nice to have around for tricky placements.

One other note - if you don't know if you'll need an offset and your tight on cash, consider getting the DMM offset nuts. These work almost just as well in flaring cracks/pin scars.

That's kind of what I was thinking. I have used tri cams for some of those odd placements you talked about on a rare occasion, but I figured I would stay on track with what I have been building so far. I have a set of stoppers, doubled in some sizes, 1/2 a dozen tricams of various sizes, and a set of C4s from .3-2. It seems to be doing okay so far. Would like to get a couple of cams a little larger than 2, maybe double up on the .5-2 and look into some C3s or equivalent small cam in the future, but excited to climb with what I have for now. Thanks for the advice. Nice to be able to do some research here

First off, you don't NEED offset cams. That being said,

In pin-scarred routes in Yosemite and the flaring pods of Joshua Tree they are fantastic and can turn "sketchy" into "bomber" I carry a set in addition to my normal rack as they don't add that much weight and have never reached the top without placing at least one.

For aid climbing they can be the difference between C3 and C1 and are essential to getting a clean ascent of many harder routes. With these in a pin scar, you can go further on sketchy gear above it, without one of these, often the hammer can be the only way to keep from falling apart.

That being said, if you're building a trad rack, these come last. Normal cams are going to be the better placement on a larger percent of the climbs you do unless you're climbing specifically in places like JT or the valley.