I belong to another rider group and one of the leaders just posted about how he was tired of going through rear tires every 6 months or so (He says he rides alot). So he installed a car tire (Cooper ZEON ZPT 215/45R18) on his bike (VTX1800F) and included a pic of it. Now I'm no motorcycle gure/expert, but that just doesn not sound proper or smart.

First of all, I don't think a car tire is designed for the leaning/cornering that a bike normally does.
Second of all, along with above, there is no "tread" on the sides of the tire. I would think that's a problem when cornering in less than ideal road conditions.
has anyone else ever done this ? It just sounds like a really bad idea. I'd be leery of riding behind him.