I've been having issues with my handlebars slipping on my cyclocross bike, so I was thinking about replacing them because I don't really like them anyway (a bit too narrow, drops too deep, etc...). I think my stem diameter is 25.8 (It's a Ritchey stem). I have no idea about the diameter of the current handlebars.

Can I use a 26.0 diameter handlebar with this stem or do I have to get something 25.8? It looks like I have many more options in 26.0.

Thanks

25.4 is mtb, 26 is standard road. You can't really use 26 handlebars with 25.4 stems. Dimension and nitto make 25.4 drops, but you'll find more options in 26.

I was wondering about 25.8, though, not 25.4. Would I be better off just switching to a 26 stem and going from there? I'd rather not have to replace the stem in addition to the handlebar.

Never heard of a 25.8mm stem, but have for bars. 25.8mm is supposed to be the unofficial in-between size for bars that can be used in either 26mm or 25.4mm stems.

If the parts were stock on your 'cross bike, they're probably 26mm. Replace the bars if they don't fit you well; you'll most likely want a 26mm bar.

Well, I'm not entirely certain that it's 25.8. The sticker on the stem is partly scratched off, so it says 25.something. Based on what's left of the number right of the decimal point, it has to either be 25.8, 9, or 0. It's definitely not a 4, however. I had read online that the standard Ritchey bar diameter is 25.8, so I just assumed that was it.

The bars and stem aren't stock, so I'm not sure. The stem is definitely aftermarket, and the bars sort of look like they were pulled out of a junk bin somewhere. I'm wondering if the slipping I'm experiencing is because the stem and bars aren't the same size.

Yeah possibly. Most drop bars are 26mm. If your stem is 25.8mm, I would think they'd be fine. On the other hand, if it's a 25.4mm bar, use a single sheet of aluminum from a beer/soda can wrapped around the bar. Are you certain the problem is not just from an under-tightened stem?

Is this a quill stem or a pop-top?

It's a pop-top. I originally thought the problem was an under-tightened stem, so I tightened the HELL out of it. It helped some, but it still slips. I thought about trying the soda can shim, but there's already a gap between the stem and the faceplate when I tighten the bar in. I figured I wouldn't want to make the bar any bigger. Should I give it a shot anyway?

How big of a gap? There should be a gap between the faceplate and the stem otherwise it'd bottom out and you'd never be able to get it tight enough. Judging from earlier posts I'd try the aluminum can shim, if the shim works then you know you should get a 26.0 bar.