OK, I'll bite ...
... Here's something to make the trolls gnash their teeth about. Normally I don't do this because it goes counter to what I tell fellow "darksiders" but I will repeat it again:
Words of wisdom to the intrepid souls that decide to use a car tire or any other modifications they may make to their bike for that matter: Be bold. Experiment. But do so informed as well as you can be and know that consequences for really bad decisions can be dangerous and damaging and ideas that are successful are worth sharing.
And I also say GO FOR IT!!!
If it works out, then good for you. It won't matter what anyone else says when you KNOW you are right about your decision. Be quietly satisfied with yourself, speak honestly and modestly of your success and let the naysayers eat crow.
Having said that, here goes anyway
I was the first to start using car tires on the Honda Reflex back on June 6, 2008. I took a lot of flack from naysayers for quite a while and had to debunk a bunch of myths and correct many misconceptions. But now there are several Reflex riders that have safely and successfully been using a car tire on the rear. Some wishing they had known about it sooner and none that I know of have gone back to using a regular scooter tire on the rear. Some swear by it while others will just swear at it. Still frowned upon by some, but it is becoming more of an accepted practice; well, tolerated at least.
I'm not crazy, stupid nor too cheap to buy "real" motorbike tires for my ride, I merely choose not to. And if one does not do things within the scope of influence, advice, knowledge or even without the approval of designers and engineers do things necessarily become automatically dangerous. Knee jerk reactions are seldom correct. (and there do seem to be some reactions when this subject comes up still.) Engineers and the rest of the so called educated don't know everything and theory is often a paper tiger. Besides, this world is full of educated idiots. Experience and first hand knowledge are a better and truer gauge because they demonstrate the truth in an absolute and undeniably solid way.
And the preponderance of evidence thus far (and there is plenty of it) has shown that using a car tire is not unsafe.
Railing against a thing because it does not fit a certain conceptual mold is of the same genre as trying to kill what one fears only because of the single reason that they don't understand it. The narrow minded are called that for a reason. I think Albert Einstein said it best: "Great ideas often receive violent opposition from mediocre minds."
Just one other thing to note about tires I use on my Reflex scooters and that is I also use a 150/70-13 Pirelli DIABLO scooter rear tire on the front of my Reflex scooters.
This is the same size REAR tire for the Honda Silverwing FSC600 scooter. Naturally it is taller than the standard 110/90-13 Bridgestone Hoop. But it sticks like stink to the road, handles bumps, soft sand and gravel better IMO. Plus it helps level the bike a little better with the tall tires on the rear. It will wear much longer than the standard size tire. No problems when braking nor has any tendency to hydroplane been noted when riding on wet roads.
Surely I'm not the only one who thinks outside the box.