I've never understood why this is an issue. Of course it is a convenience when a pipe passes a pipe cleaner. I'd say about half my bent pipes pass pipe cleaners, and I am proud of them for that. In other cases, the turn is too great for a wire to bend around, and then I just clean that portion from time to time when I remove the stem, and I feel no need to do it every time. I know some smokers claim they can crimp a pipe cleaner so it will pass through any bent pipe, and more power to them, but this is not my experience, and I have tried various times and various crimps, just for sport. With bent pipes that don't pass a pipe cleaner, I say, don't worry about it. Enjoy your smoke. Many fine pipes don't pass this test. To me, it seems a silly concern.