Proper innertube size?

I just pulled my muni out of storage after almost 3 years to discover that there is a giant leak in the valve stem of the tube. To be expected I suppose, but a little annoying. I cannot remember what tubes I’m supposed to be using in this guy though, so if anyone could help that would be fantastic. It’s a 24" AlexDX32 rim using a stout 24x2.60 tire. I vaguely remember a ‘24" extra thick’ tube, but confirmation would be great.

I do have a 20" spare tube sitting next to me, which I’m assuming would be a bad idea to use on the muni?

Thanks

Ideally you would use a 24X2.5-2.7 downhill (extra thick) tube. If you haven’t had trouble with flats you could try a thinner tube but if the tube has to stretch to much it could feel sort of crappy.