Stem confusion

Fairly sure I'm going to sound like a clueless idiot, but I'm a little bit confused about stems and bars.
I've been thinking of buying a new frame and fork, with a 1" threadless fork, and after a fair bit of confusion about which stems will fit it, I'm now confused about stem clamps and which bars will fit which clamps.
After looking about on Planet X for a while, I'm confused as to why they have so few 25.4mm stems when it seems to be such a common size for bars, but they have plenty of 26mm stems and no 26mm bars, or will you be able to run a 25.4mm bar on a 26mm stem and that 0.6mm make no difference.
Tl;dr, clamp sizes make no sense to me.

http://sheldonbrown.com/cribsheet-handlebars.html

This is pretty handy, although I think 31.8 has become waaaay more common since he wrote that. And Planet X often don't seem to make much sense.

Thanks for that, that cleared up why there's so many sizes anyways.
Any idea whether running 25.4 mm on a 26mm stem would work, or if a shim for this purpose exists?

Shims exist: http://www.velosolo.co.uk/shopbar.html (most of the way down that page)

I've heard you can make one with a coke can as well. This is probably less safe than a real shim.

Somebody more knowledgeable than me on here will probably know what to expect if you use a 25.4 on a 26 without a shim, but I suspect it will either be your bars slipping all over the place or death under a bus.

coke can is fine for 25.4 bars in 26mm clamp

don't run 26mm on 25.4 stem or vice versa.

both will eventually cause damage to your equipment and potentially be dangerous. even if you *can *do it.

Yeah I had a look for some shims after posting, and yeah, that was what I was worried about...the whole death situation.

I'll probably just end up buying some 26mm bars then, seems to be the easier/least dangerous option.

I've run 25.4 in 26.0 and 26.0 in 26.4 with no real problems, both times shimmed with a Coke can. Never died.

Edit: It also depends on the bars you want to run. I'm pretty sure you'll be hard pressed to find 26.0 riser bars, as opposed to 25.4 or 31.8, but (most) of the older Cinelli bars are 26.0 or 26.4. Nitto drops are 25.4 for their NJS track drops and other bars, but they also have some of their other models in 26.0.

Confused?

You can also run a 1 1/18 stem on a 1 inch steerer with the right shim, life will be easier if you just go for 31.8mm clamp from the start. 1 inch ahead stems aren't as common as 1 1/8th.

If you use a thompson elite (with steerer shim obv'), I think you can switch between 25.4 and 26 faceplates to suit different bars. Does anyone know for sure?

Just sayin.

I figured out the bit about steerer shims and all that after finding pretty much no 1" stems.

Yeah I've decided to just go for a 25.4 stem, seems waaaay easier as there seems to be plenty of bars and not much hassle.