On Mon, 20 Jun 2011 09:32:21 -0700 (PDT), gcotterl
wrote:

I'm trying to replace the inner tube in the tire of a "Radio Flyer"
child's wagon.

I've removed the wheel from the wagon, worked the tire off one side of
the rim and removed the old inner tube.

The new inner tube is twisting when I work it into the tire. Should I
partially inflate the new inner tube first?

Yes. On a bicylce too. Enough that it straightens but doesn't
inflate. Not so much that it interferes

Do I put the valve stem through the hole in the rim before working the
rest of the inner tube into the tire?

Yes. Make an effort to work the tire in evenly on each side of the
valve, to keep the valve pointing straight to the center. This is
1000 times more important on a bicycle than on a wagon.

Once I get the inner tube into the tire, how do I get the tire back
onto the rim?

It's amazing how getting it on can be harder than getting it off.

And it may be that it's harder for smaller wheels, I don't know, but
if there is stretching involved, maybe there is less stretching.

Start at the valve and use your thumbs to push the tire inside the
rim, alternating from side to side and working away from the valve.
At the end, screwdrivers are too sharp, you may need s bicycle-size
tire-iron, but since you'll never do this again, use the handle of a
spoon, like a cheap stainless steel soup spoon, not with a handle that
is pointed at all but a wide rounded handle or even one with a wide
rectangular end if it has rounded corners and edges. To further
protect the tire, don't push the spoon handle more than a quarter or
half inch past the end of the metal rim, under the tire. Then lift
the spoon and you will likely not be pinching the tube. I guess you
should uninflate the tube as much as possible before doing this, but
with bicycle tires, I don't.