adipe

rim radius is about at least 0.35mm reduced due to spoke tension that is not even of a quality build. a low spoke tension variance (with total radial runout of 0.1mm which can be achieved with the same lateral runout) affords higher spoke tension. plain gauge spokes make sense with higher spoke tension than butted spokes. you either go with 2mm DS and 1.65mm NDS OR 1.8mm DS and 1.5mm NDS for example. but the first choice of these two require more tension.

IF you have butted spokes on the NDS and you tighten those nipples temporarily you may be going past the yield point of the spokes so that the torsional stress makes them twist in the non-elastic manner. you also might find that when you bring the tension back you will have the wheel screwed up.

ONLY if you are a skilled wheel builder should you think about messing with spoke tension.

rim compression can be computed from these:
1) the section of the rim: ~90 square millimetres of aluminum material. that's for a 622mm 470g rim aluminum having 2.7g/ccm density;
2) the radial component of spoke tension (isolate the x,y,z component of the vector for both flanges) and ultimately dividing the total spoke tension (from all spokes, radial component that is) by 3.14 and for a 32 spoke wheel you could have say 1000kgf of CIRCUMFERENTIAL compression stress. and even the tire pressure adds a bit more to all this compression stress of the rim, depending on the size of the tire and rim as well.

the Young modulus of aluminum is about 72GPa in compression so you get the stress of the rim divided by this modulus and you get the rim compression
stress of the rim is 9800N/90sqmm=108.9MPa;
and if the rim would have a radius of 300mm:
108.9/72000*300=0.45mm rim compression due to a 0,0015125 compression factor:
108.9/72000=0,0015125

Whit51 

The Cool Stop Bead Jack is worth getting, and it’s relatively inexpensive. I had a hell of a time mounting some Panaracer Gravel Kings a year a go and dreaded the day I had to change a flat. I finally had a flat and the tire had stretched with use - went back On the rim with thumbs only; no levers, jacks or soap solution

adipe

you don't need soapy water; you need talcum powder and technique.

you press the tire bead into the rim channel leaving the valve for the last part and do not ever start with the valve going the other way around.
you need to put the wheel on the floor with the valve down and pull the tire towards your head keeping something to hold the wheel down as you pull only the tire to force it to go as deep into the rim channel as possible.

just put some stick or a piece of rope in between the spokes if there's too many spokes and you cannot get to hold the wheel just by using both feet pressing against the rim laterally (it helps to either use the thumbs of your feet or soft shoes etc.; a rope that you can stand over and keeps the rim down is an idea for you to get the picture)...
press on that stick/rope with your feet holding the wheel down as you pull upwards on the tire; start pulling the tire upwards from 9:00 and 3:00 to first force the tire into the rim channel and go gradually and finally pull from 11:00 and 1:00 to not only keep the tire bead overall in the rim channel but also have the bead stretched elastically as to make the tire as much eccentric to the rim as possible... and you'll pop the tire into the rim without even using tire levers.

wherever you pull the tire press on the beads to seat it while you also pull it radially to get that eccentricity. you should try this technique in maybe two stages, making sure you are seating the tire bead in the rim channel at the opposite side from the valve where you end up. you could try using tire levers if necessary to temporarily keep the tire in tension at the valve when you go the second stage, pushing the tire bead with your fingers together to meat on the rim channel at that opposing part of the valve and goiing this way all the way towards the side where you finish, where the levers would be. you may find out that the tire levers have become loose from the seating of the tire rim in that channel and this will show you that you did not really need the tire levers because the technique works even without tire levers.

i usually pick tire levers only when getting the tire off the rim but even then i help the tire beads meet on the rim channel first all around the wheel and pop the tire out the rim near the valve.

if you use tire levers without this technique the friction of the tire on the rim locks it and prevents it from stretching while gliding on the rim all the way from the opposite way to where you end up; the tire bead will be stretched on a much lower portion of the rim.

some press on the tire downwards, towards the ground, but the tire will slip back a bit as you lift the wheel off the ground when you finally get to the bead to pop over the rim.
this is not what i would usually do because the tire will slip back if i go towards the ground. so, i rather pull the tire upwards

so, my suggestion is to work the opposite way of what this video shows (not goind downwards but upwards but you need to press the rim down with your feet etc. so you end up working at the valve that will not be down at the ground but at the top) - watch from 1:00 to 1:30

_ForceD_

Well, I got the Kapton tape that was suggested above (actually ended up with the 'knockoff' brand "Koptan" tape thanks to skullduggery of the internet merchant. But oh well.). The added few millimeters it provides does make the wire bead tires easier to mount onto those old rims. But the folding tires still aren't going on.

Dan