On my prior bike (Bianchi Volpe) with 23c and 25c tires at various times, I've never had a problem getting the tube to "fit".
I know they come in various thicknesses and a specific tube will cover a size range, like 21-25 or something, and I know I've used more than one range on a given tire.
But I now have a Felt 35 with Ksyrium Elite wheels and Hutchinson Carbon Comp tires. Today I had to fix a flat and I do what I always do - just remove the old one, replace it and patch it later. Well, when I put the tube in and pumped it up, I saw the tire didn't get seated in the rim where the stem is. I deflated and tried repeatedly to seat it without success with two different tubes. It just didn't seem to have room to get pushed down far enough.
I noticed the tube was thicker than what came with the bike. I do not know what size range they were, but it is possible if they covered the higher end, that would further contribute to the bulk. Putting in a tube that came with the bike that I had patched earlier worked fine.
So, anybody have experience with this? Are these wheels more sensitive to what tubes I can use or is there some trick to this?