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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.?

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    Noise and cost. Commented Jun 22, 2015 at 18:48
  • so is a timing chain more noisy than a timing belt ?
    – amphibient
    Commented Jun 22, 2015 at 18:51
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    Yes, that was why the change was from Chain to Belt, Chains have been used long before belts were. Belts are quieter and cheaper. Commented Jun 22, 2015 at 18:53
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    @Movemorecommentslinktotop - Make your comment an answer, because that is exactly why and you know it's the right answer. Commented Jun 22, 2015 at 20:42
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    ^^ agree with @Paulster2
    – amphibient
    Commented Jun 22, 2015 at 20:42

2 Answers 2

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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
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  • Great point, it wouldn't be easy to protect the chain from the environment. Commented Jun 22, 2015 at 23:53
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    Kevlar belts provide a more suitable alternative to steel belts. Lighter and just as (if not more) durable. Commented Jun 23, 2015 at 0:58
  • @Paulster2 : Didn't know that Kevlar was an option. Thanks for the education.
    – Zaid
    Commented Jun 23, 2015 at 6:46
  • Oh, come on. Timing chains and belts are inside the timing case - they're lubricated with engine oil and don't spray oil all over the engine compartment. I've got 50+ year old tractors that use timing chains (1948 Ford 8N and 1965 Ford 3000) - both have a timing chain, and neither one has oil spraying out of the front of the engine. Commented Jun 23, 2015 at 11:23
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    @BobJarvis Yes but the OP asked about replacing the serpentine belt with a chain, which unlike the timing chain would be difficult to lubricate and protect. Commented Jun 23, 2015 at 11:51
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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.

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  • I massively disagree with 'the less reliable belt' I have never seen a timing belt failure before its recommend life but I have seen dozens and heard of thousands of chain failures way premature of the manufactures recommended life. BMW & Ford diesel, PSA & Opel petrol all have issues with chains either failing or stretching Commented Dec 9, 2017 at 19:31
  • @TerryGould maybe I should have said less durable. Chains last the life of the engine, while some belts are changed as early as 60,000 miles Commented Jan 24, 2018 at 23:47

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