If Iyou have heavy cruiser, or tourer , and was doing miles in flatistan, just do it, so much cheaper...
Unlike bike tyes car tyres are designed to flex in the sidewall. This flex will work to keep the tread flat on the gound, just like it does in cars.
You can see it in the video, even though he dosnt corner very hard. so the handling of a bike is just fine, even flip flops, nige.
On a sportier bike high lean angle would see corner of tyre lift, this would feel like a bike tyre worn flat in the middle. but contact patch would still be bigger, till you go to far..
With all 3 wheels allegedly on the ground, sidecar is different kettle of fish, that side wall flex is used, how it was designed to its full extent.
Main reason on sidecar is rear wheel sideways slip n spin is a cornering aid, so bike tyre lasted just 3000K car tyre 35000 still going strong.
Now the saftey nerd warning,,
the profile of the tyre beads is slightly different between bikes and cars this makes tyre hard to seat. make sure its on. 17 is a common swap and often done, 18 19 well good luck finding a tyre that fits in swingarm.
For 15 inch rims (often found on crusers) the diameter is actually different with the bike rim being slightly larger. never fit car tyre to 15 inch bike rim if you do the bead is over strecthed and will bust or break, some times during and sometimes after the fitting process. ie in use!
For the sidecar I use a 15 inch car rim, mounted to the bike hub seemingly ideal, but it opened a can of worms with insurance and the need for engineering..
Cheers John