The old Corollas in the 70s and 80s had timing chains. In the 90s, Honda, Toyota, and even Nissan started making belt-driven cranks instead of chains. Now they are back to timing chains. What happened?
In: Engineering
Chains are an overall better option but come with some significant drawbacks. Belts may not be as reliable, but they’re cheap and easy to replace because they’re accessible on the outside of the engine and only a few covers have to be removed to get to them. Timing chains are more reliable but they don’t last forever, and accessing them requires partial dissasembly of the engine which is more time consuming and more expensive. In both cases the failure of the chain or belt leads to catastrophic failure of the engine itself. Belts made sense because diagnosing a worn belt is easy and changing it is much cheaper and easier, so this creates a benefit for the owner where it’s making one of the most crucial service items cheaper and harder to ignore. But as technology has progressed chains have reached great levels of reliability and longevity and lubrication and tensioning systems are also far more effective and reliable themselves, which used to be a weak point in many engines for decades. At this point a timing chain can last long enough that when the time for it to be replaced comes, the cost of this replacement is overall cheaper than the cumulative amount spent on belt replacements will have been for the same time period.
It’s also worth noting that motorcycles have almost exclusively used chains in the majority of models for decades now, with only a few, notably Ducati, sticking to belts, which in turn has led to the constant development and refinement of timing chains.
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