First I had to figure out the sizes of my old stem so I could match. Some of the Stem Measurement guides just made me go WTF. Fortunately I found some nice clear ones like : this and this . So, yeah you just measure the stem along the bar that goes from the steerer axis to the handlebar axis. Road bike stems have a 73 degree angle, which makes them horizontal, a 90 degree stem will point up from the headset. This also had me confused for a second. If you changed from a 73 to a 90, the handlebars will actually do different things when you turn. Road bike handlebars actually dip down when you turn, they sort of lead you into leaning in the right direction. Neat!
Then you have the issue of all the tube diameters. Fortunately Sheldon has that sorted . The steerer tube part is almost always the ISO 1" size (which is 22.2 mm ; I know it should be 25.4 mm, but the 1" refers to the outside of the head tube, while the 22.2 is the diameter of the stem that fits into that). The handlebar diameter is a bit of a bigger problem. My bars don't have any label on them so I had to measure. The common sizes are 25.4, 25.8 or 26.0 mm. Of course I don't have calipers, so the easiest way to measure a diameter is by measuring the circumference with a piece of paper. Hah! Good luck telling the difference between 25.8 or 26.0 with a ruler. Anyway I know I don't have 25.4 , and the 25.8 and 26.0 are considered interchangeable.
Now I finally know what I want. A 22.2 mm - 26.0 mm stem with 100 mm reach. Sadly, the vast majority of cool old quill stems look like this . They have one bolt and the handlebar clamping bit wraps all the way around - you can't just take the handlebars in and out the way you can with modern threadless stems that have face plates like this . What that means is I would have to take off my brakes/shifters and hoods, take off my bar tape, slide the bar ends through the hole and twist it around, then put everything back on. Umm, no thanks, I'll have a face plate please.
Okay, I so I need a 22.2 mm - 26.0 mm quill stem with 100 mm reach and a removable face plate. Okay, let's track one down. Well, they do exist. One popular model is the Salsa SUL which is highly recommended various places. It's been recalled due to catastrophic dangerous metal failure. Umm yikes. Hmmm, well lucky me with more searching I tracked down another. The Deda Murex. Umm.. reputed to fail to hold handlebars , very loose and flexes easily. Umm.. okay, I found another, the Cinelli Frog ! Urg, same problem as the Deda.
I thought I found the mother lode at two cool eBay Stores : New Old Stock (NOS) and Mario's that have lots of classic bike gear. I started looking at a 3TTT Motus. (BTW 3TTT is is the most fucking retarded name ever, it's like Mount Fuji or something, and people either write it as "TTT" or "3T" or "3TTT" which annoys the fuck out of my Google searching). So the 3TTT Motus ... many cases of catastrophic clamp failure, strongly advised against. Yay. I think the Mutant might be fine, but I can't find a 100mm mutant.
Finally I found one - the Profile H2O ; it's a very common cheapo stem, I ruled it out at first because I only saw 90 and 105 degree models for the mountain/casual market. Then by chance I discovered they do make a 74 degree, so here I am. A full day later and $1000 of my time down the drain, I now get a shitty down-market aluminum stem.
BTW this might be the worst web site design ever. Oh yes, I know what this text needs - rotating and wiggling to make the viewer sick! And it should take forever to settle down so you have to try to read it while it wiggles or just sit there for minutes. To whoever made this : be ashamed.
I have a much worse problem upcoming with my around-town bike. It's an old bike in the 28.5" size which doesn't exist any more (it's all 700 now - BTW don't take those measurements too literally, they often don't actually correspond to anything that's actually on the bike). There's a lot of stuff I should do to fix it, but the parts are rare and expensive. I suppose I should give it away and get a new one, but it is an old CroMoly lugged frame that hardly exists any more except from bespoke custom builders.
I quite enjoy working on bikes. It's so much simpler and cheaper than working on cars, you can get all the tools you need for $100, and it's very satisfying to fix something with your own hands, and it brings you closer to your machine, you get to know how all the bits really work. I've written this before.
Sadly Seattle is an awful place to bike, but that's another rant. I'm still going, cuz hey, I still love biking even though the pavement quality and traffic and bike routes and countryside accessibility all suck balls here. It's like sex with a condom; yeah it's fucking awful and if you can have real sex you should, but if all you can get is sex with a condom, then you still do it. (people who tell you "well then don't do it" when you complain about something are fucking morons).