Should I be worried if an inner tube seems too small for the rim?

Question

I recently changed a flat tire on my Raleigh ladies shopper bike (tire size 20" x 1 3/8"). Although the box for the tube was labelled as the correct size, the replacement tube was so small I had to stretch it to get it on the rim, even when slightly inflated. This is the first time I've ever known a tube to be smaller than the rim -- usually they are a couple inches too big and you end up stuffing the tube slightly doubled up into the tire. Having now inflated the tire to the correct pressure, the beading on the tire is no longer flush with the rim in at least one spot. I have deflated the tire a couple times to ensure the bead was under the rim, but it still looks rather bulgy. Is the tube possibly too small? Has anyone ever had a similar experience? Can I safely ride the bike or do I need to replace the tube? And if the tube is not the correct size, why would it be labelled as such, unless this is a real mix-up at the factory?

Answer 1

That doesn't sound right, the tube is also stamped with the size. I'd check it out. It's possible the wrong tube got put in the box. You are right, a tube should easily go over the rim. With the tube stretched like that it will likely pop or flat quickly.

Answer 2

Certain tires/wheel combinations have nothing to do with tubes. Bring the tube back, it won't last.

Answer 3

Certain tires/wheel combinations are denoted in fractions and others in decimal.  These are not interchangeable generally.

A 20 x 1-3/8 will not work with a 20 x 1.5