Originally Posted by DigitalQuirk
One issue that immediately springs to mind is brakes. A moped, with an engine and tank of gas, is a lot more mass to stop. Your side-pull calipers probably aren't going to cut it. Another issue is traction. Chances are good that a bicycle tire will be very apt to spin while accelerating. Then there's stability. A bump or pothole with the force of the weight of a bike behind it going 30 MPH can be hairy enough; at 50 MPH, with the weight of the moped, it will probably get destroyed. Then there's the fact that the tire wasn't designed to handle all that weight in the first place, so it will probably warp in very short time.
Personally, I'd go with a harder rubber compound with a smooth tread for maximum fuel economy on a moped; you'd be a lot further ahead.
Very good advice. All sound points there. I actually had a motorcyle front tyre blow out on me once when I hit a bad pothole at only thrity miles an hour. It was a very unfunny experience having no control at all. The damned thing changed lanes and threw me off into the road. I don't take liberties with tyres now.