This reply about belt-driven belt got my interest here. It does not need lubrication at all according to the replier. What are other properties with belt-drive chain? Where does the idea come from? Are belt-driven chains used in cars or some machines? Are they durable? Do they last in all kind of weather? Like in freezing winter to sunny summer? Do they stretch like steel chains? When should you change them?
The main difference with belt drive is that you can't break the belt, so you need a specially built frame that allows the belt to be fitted. On a chain-driven bike the chain usually runs though the frame between the seatstay and chainstay. This makes retrofitting a belt drive impossible on most bikes. Similarly, you're limited to the belt lengths available from the manufacturer.
I have seen bikes with exposed belt drives but that does not seem like a good idea to me. Once you get mud or dust in there it's going to grind away the belt and pulleys, and parts are usually expensive (because they're uncommon). I don't know much about how they wear as I've never seen one that's had much use (which in itself should tell you something).
Once the belt is fully enclosed it becomes just like an enclosed chain drive, except that it can't be serviced by bike shops. I suspect this is the real deal-breaker for most people.
Belts usually have higher losses than chain drives, making them unattractive for high-performance bikes and hindering their adoption in other bikes (because much of the profit for bike shops is in the more expensive bikes).
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I've never ridden a belt-drive bicycle, but I've ridden both belt and chain drive motorcycles and the belt drive is considerably smoother and quieter.
One of the features being used to tout belt-driven bikes is that they don't require lubing, so that would be a plus. In addition to not needing to take the time to properly lube your drive-train, the lack of lube would mean less attractant for dirt/dust etc.
Each manufacturer would probably have their own recommendations about operating temperature range and how often to change them.
Belt drives can't be used with derailleurs so the bike will be single speed or need an (expensive) hub gear.
There were some cars that used a belt drive, usually with a v-belt and split pulleys to give a continuously variable gear - haven't heard of any bike doing this.
Main differences compared to using a chain:
The idea is very old. It was used in the first steam engines (and probable even earlier).
Yes, they are quite common. In particular, the alternator in a car is usually driven by a belt.
I don't know specific numbers, but they should last at least as long as a chain, and modern belts should have no trouble with high/low temperatures (they are used in cars as well, after all).
Actually, steel chains don't strecht (noticeably), the just get longer from wear. Belts on the other hand do strech under load (see above).
No idea, but they should last considerable longer than a chain (less wear).