Otdfbt

I got a 700x18-23 inner tube that just got punctured. The small round patch on my patch kit is a bit wider than the inner tube itself. Is it ok to cut around the patch so it fits?

An added question: when buying an inner tube, should i buy the smaller 700 x 18-25c, or the 700 x 25-32c for my 25c tires?

Don't cut it. The patch is thinner at the edges and cutting leaves a thick sharp edge where it can tear. Roll the tube sideways and you can glue first one and then other edge. There are smaller patches that are made for narrow road tubes.

My experience has been the same as zeus; I've been cutting those bigger patches in half for decades.

However, I have had a couple of these peel up on the thick cut edge, long ago. That led me to taking more time with such patches: making sure that the tube is well abraded and partly inflated, that the glue runs right to the edge, that the edges are firmly pressed into the underlying rubber. With these precautions, I never lose air on a cut patch.

However, if I was stuck doing a roadside repair, I would always choose a whole patch.

(As an aside, why do they include those monster size patches in a bicycle tube repair kit anyway? If a hole was big enough to need a patch that big, you'd never be patching it.)

You don't need to cut it just because the patch is slightly wider: you can wrap it around the tube. Just before I put the patch on (that is, when the applied glue dried somewhat), I pump up the tube a bit so that it expands roughly to the size it would be inside the tyre. This allows to apply the patch easier, esp. if it's oversized, and also presumably avoids unnecessary stress (or rather, stretch) on the patch at full pressure.

That said, I frequently cut patches. The typical kit contains several long patches which never get used in full: if you have a cut that big, it's better to replace the tube. So I cut them in 3-4 smaller pieces. I never had a problem with the sharp cut-off edge, whether I put it along or across the tube, even on the 700x23 high-pressure road tyres. And I have decent statistics: I estimate roughly 10000 km with at least one patch cut like that.