Why not have drive chains instead of drive (serpentine) belts?

Question

My drive (serpentine) belt was recently chewed down to about half the width and I had to replace it.

Which brings the question: if the automotive industry has been gradually replacing timing belts with chains (my Tacoma has a chain and the model just a couple of years older had a belt), why not use a chain also for accessory driving purposes and replace pulleys with sprockets on the alternator, AC pump etc.?

Answer 1

Here are a few factors besides the ones already mentioned that don't work in the favor of chains:

• chains need lubrication. Do we really want another grease/oil in the engine bay?
• pulleys would have to be replaced with sprockets. If some debris finds its way in the engine bay and lodges itself in a sprocket you can look forward to broken teeth in case something goes awry
• chains are not as flexible as belts. Wrapping one around 5/8 of a sprocket is going to be difficult, so the packaging of the engine auxiliaries will be less compact
• giving chains tension ain't easy. The chain tensioners I am familiar with rely on hydraulic pressure to keep the timing chain ship-shape
• chains will have a lot more rotational inertia compared to belts. That is undesirable
• steel belts (or Kevlar equivalents) are a more suitable alternative to serpentine chains

Answer 2

Noise and Cost. It's really that simple.

Chains used to be the most common device used for connecting the timing gears. Somewhere across the way someone told the consumer that cars shouldn't make noise and so the cheaper and less reliable belt was used by the manufactures. They did the same with direct drive (gear to gear) when they went to a fiber gear that also failed much sooner than the metal gears but were less noisy.