My own persona code of conduct:
Never wear the shirt from the current tour that you are currently watching.
Do wear a shirt from a previous tour. The older the better.
If you don’t have a previous tour shirt wear one from a band that in some way is linked to the band you are seeing.
If all else fails a Motörhead shirt is appropriate for all concerts.
Alternatives:
Stones
AC/DC
Ramones
I’m curious as to why some people care about this
Are you new here? Why does anybody care about 90% of what we talk about? Why do you care that other people care?
I don’t know if there is much of a story behind it. It’s a shirt that looks like it has the logo from the first Rush album across the chest, but then on closer inspection the U is actually an A. I assume Geddy had them made as a gag. He was wearing one when I saw them on the Time Machine tour and I’ve seen lots of photos and video with him wearing the shirt.
Ok. I thought it might not be anything more than that, but wasn’t sure. Thanks.
Never heard of this “rule,” and I find it utterly ridiculous.
Next you’re going to tell me I can’t wear a Cubs jersey to a Cubs game.
Hehehe, I don’t make a living at it, but sure.
Hehehe, Telecasters, at dawn! Wear a nice suit.
“Metalhood” was mentioned up-thread. 
In high school art class, I, not particularly artistic, picked a famous picture for my screenprinting project. It was the picture of Ozzy Osbourne holding up Randy Rhoads by Randy’s right leg, while Randy plays guitar. It’s an iconic photo for Ozzy and Randy fans, and was instantly recognizable among us in the '80s. It’s on the cover of the Randy Rhoads Tribute album. I blew up the image into a big, black, detailed silhouette, and it covered the front of a plain white t-shirt, with a simple 1956-1982 under the silhouette with the most metal, Gothic font I could find. I’m not very artistic, but I can trace well and run a razor knife smoothly. It really came out awesome.
I wore it to many metal shows in New England, and I can’t remember how many times I got stopped by strangers, with a “Doooooood! Where’d you get THAT!” I was so proud to tell them I made it.
Most other times, I’d start a show wearing some sort of metal shirt, but finish it wearing a shirt I bought at the show, because putting it on was easier than carrying it around.
So much as there is “logic” to all this: Sporting events are a bit different because it’s a competition, and you want to identify with the side you’re rooting for. Not everyone at a Cubs game is there to cheer on the Cubs, so you want to show which team you’re loyal to. With a concert, it’s not a competition–presumably, you’re at a Metallica show because you like Metallica, so the idea is “yeah, we all know you like Metallica, since you’re here.” It is somewhat analogous to the post before about being a tourist wearing a tee-shirt of the city you’re visiting when you’re visiting that city.
Like I said, I personally don’t care, and don’t think oddly of people who wear shirts of the band they’re going to see – though I do have to say if it’s a shirt of the current tour, that does strike me a bit weird – but that’s the logic, so much as there is, behind it. Plus, like I said before, when I was in my younger days, I did enjoy finding other bands I might like by perusing the tee shirts of fellow concert goers at shows I was attending, so why not pimp another, perhaps lesser known, band you like?
90% seems awful low
It’s funny you mention Maiden. It seems the one band where the “Lame, because reasons” rule doesn’t seem to apply is Iron Maiden. Their fanbase seems to revel in wearing Maiden gear to Maiden concerts. I wonder if the revert to the rule when attending other band’s concert.
MeanJoe
This site’s slogan has to do with fighting ignorance. Wondering why something is so is part of a fight against ignorance. The idea that personal preferences are things that just mysteriously manifest themselves and cannot be questioned is bunk.
Preferences have origins and reasons. I want to know why the people who care about what’s on their or other people’s T-shirts at a concert have preferences, why do they care.
I often ask why people care about something or prefer something (or not). It opens doors into other people’s minds. I learn about different ways of looking at things, which means I can sometimes see things differently.
Preferences are also not set in stone. Thinking and talking about them can result in changing them too.
I like that we’re fighting ignorance by “wondering why something is so”. And so few people wonder why they themselves do things.
In my case, I’m realizing how many times I decide what to wear because subconsciously I want people to notice it, and maybe think I’m cool.
NOOOOOO… that’s a really uncool attitude. What can I do to stop? Is “notice I’m doing it” good enough? I’d hate to have to trade in my Obscure Band Shirt collection for Wayne Newton World Tour shirts.
…
Something I noticed. Some of us don’t have shirts without band names on them. Some of us only have metal bands. And metal bands we’ve paid an arm and a leg to see, then the other arm for the tour shirt. Look at Loach’s potential choices of what to wear:
Note to self: I’ve got a few blank t-shirts, some white, some black. Was going to print on them, but I think I’ll just start wearing them, and practice not giving a rat’s scrotum what anyone thinks (hmm, they’ll think that’s cool… d’oh!)
I wear something lightweight like a thin Tee to the venue. At the venue I buy shirts for the headliner, the band they’re traveling with, and the opener if they have one. Then I change into the shirt for the lowest support band. Like, I figure The Damned have been around enough that they’re only going to be impressed if someone’s got serviceable gear from the '70s or '80s, which I don’t (lost my Boston shirt in the divorce). But Radkey or The Darts might still be new enough to the scene that they’d get a little pump from seeing their gear while they are on stage.
You must not have been paying attention at the concert or you got there late. For quite a few years Rush stopped using an opening act. One tour they played cartoons. In later years they put together an amusing video to play before the show. On the Time Machine tour the fake Rush band in the video was named “Rash.” Geddy wore the shirt from the video.
