soft rattle / trickle / clattering sound when turning the wheel

I’m reassembling a used unicycle, and I’ve noticed that there’s a soft “rattle” or “trickle” or “clattering” sound when I turn the wheel next to my ear. It sounds like some smaller particles hit metal very softly, maybe as if there were fine grains of sand in the rim or something similarly unlikely. I’m not sure, the noise doesn’t come from the hub / bearings, but from somewhere along the tire… and at least the noise sounds in rythm with the wheel turning. I also believe I’ve heard that sound on b*ke wheels before, but without knowing its cause there either.

(I should maybe add that the bearing caps probably aren’t yet tightened enough, but that’s another topic and I don’t think it’s the reason for this.) Right, and I’m hesitant to remove the tire and look because my levers are probably not sturdy enough to wrestle it over the rim and back… so unless I have to…

Any ideas as to what this is and if I should worry? Thanks for your help!!

(Maybe I’ve just not used the right key words, but I haven’t found anything searching the forum… although I searched even some thread of archeological interest (1999!!!).)

Does it have a double-wall rim with a hollow space inside? Sometimes there will be little bits of metal in there, debris from when the spoke holes or valve stem hole were drilled. Harmless, if that’s what it is.

Some of the KH rims are double walled and have large (~1in) holes drilled in them. Mine occasionally picks up enough water or dirt or sand to make a little noise if I’ve got it up on a stand or something and I’m paying very close attention.

As long as it’s not coming from the bearings or audible while riding I wouldn’t worry about it.

Thanks for the ideas! It’s a Nimbus hub & rim, so it isn’t drilled, but I’m quite sure it’s double-walled. (Have they even built others?)

While I have trouble locating the noise for certain, I’ve noticed that I only hear the noise when the wheel is held “upright” (like the clock face of Big Ben), not when it’s “horizontal” (like a flying saucer). [Sorry for the weird examples, I really need to go to bed. :wink: ] That’d fit the double-walled rim explanation. - Yeah, I just don’t want to overlook some hub or bearings issue!