I am pretty set on my next bike being steel but I am open to buying a used if it is a good deal, or maybe getting a custom one made.

If I am looking at used bikes how can I tell if it is steel, alum or Ti? heck I guess Carbon might even fool me.

Magnets will attract to steel.

I purchased a Gunnar Road Sport off E-Bay two months ago.
Steel, and it's a nice ride. It's not "impress your friends" light,
mine is 25.3 pounds, but it's a comfortable ride and I am looking
forward to some day-long rides. I recommend Gunnar.

And that's nonsense.

Instead of just labeling a reply as nonsense, which it may well be to you, offer the poster some input as to how you would tell the materials apart. Magents come to mind, as previously mentioned. Are the materials welded differently, etc?

The best way to tell is to do some research on the bike - there's plenty of information out on the web for most frames, and by far the majority of frames out there are only made out of one material (e.g. Litespeed Tuscany is always Ti, Trek 5200 is always CF). Don't listen to just the seller alone. There will probably also be a decal on the downtube telling you exactly what material it's made out of, and I'd think it would be pretty rare for someone to go to the trouble of faking this.

I'd also recommend you spend some time looking at different bikes in a bike shop. You'll get a good feel for identifying different frame materials.

In general, aluminum frames do have larger diameter tubes, steel frames have thinner tubes, and titanium frames are rarely fully painted leaving segments (or a whole frame worth) of brushed titanium finish. But, these are generalizations and there are plenty of exceptions out there.

If the frame doesn't have a material sticker on it not gonna write the book..Too many possibilities and too many exeptions...

Yep, Gunnar's good and not outlandishly priced. They'll even do custom.

As for telling what kind of material a bike's made of, I agree with checking for the label first.

Good steel - 853, S3, EOM16.5.

Telling them apart - there are so many exceptions to the helpful advice I've read above as to render all of it useless.

Titanium - I own one unpainted, one fully painted. One fat tube, one skinny tube.

Aluminum - One fat tube, several shaped tube, one skinny tube.

Steel - fat, skinny, shaped, etc.

CF - skinny tube and shaped tube.

The only way to uncover what the frame you're looking is made from is research (builder's sites, ask here, etc.) Steel - sure, bring a magnet along, that will help you 25% of the time.