Just a thought. Like many I Just a thought. Like many I use washing up liquid to help mount motorcycle tyres. This is not thought of as a “good thing” as the salts in it don’t do rims much good. You can get the correct lube at m/c shops or scrounge a bit from a tyre fitter.
I am in the same situaton , sort of. I use Mavic CXP 33 rims ( as they were already built into wheels at the right price.) 25mm tyres fit ine for the road as you would expect. I also happily run 38mm hybrid tyres and 38mm knobblies. In theory they are too wide for the rim but if you look at the huge difference between rim width and tyre width on any mountain bike you can see that this works.
Off to the garage with a bottle of Fairy to swop a pair of m/c tyres now.
How does it work? The gap How does it work? The gap that is? Do you just undo the bolts and “spring the frame? Could be tempted depending on what you want for it. email me at mattsccm at fsmail dot net