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What Is The Difference Between A Timing Belt And Chain

Timing, it's what makes all the difference in comedy and it's also one of the most important things in keeping a motor running.

From the timing of the spark through to the timing of the camshaft and crankshaft; even a punchline relies on good timing.

So what is timing? And if it's so important why do we rely on belts and chains to keep our cars running?

In reality, engine timing is a really simple concept. Inside the engine is a whole bunch of rotating components including (but not limited to) the camshaft and crankshaft. These 2 shafts are used to open and close valves (to let air and fuel into the engine) and to (ultimately) transfer the power to the drivetrain.

Because the engine needs to open and close valves at very specific points in each cycle, a lot of the rotating components have to turn at a very specific speed relative to each other, much like a jazz band has to keep the timing of a song.

Interestingly, because most of the important components are shafts (i.e. they're round), you can think of each end as a clock face or a degree measurement.

Now that we know timing is important, shafts are round and we have to turn the shafts at the right speed (relative to all the other shafts), we can think about what to use to turn them.

Most modern cars rely on either a timing chain or a timing belt to keep everything in running order and they're exactly what they sound like.

A timing chain is a thick metal chain (similar to a bicycle) while a timing belt is a rubber belt that's kind of related to a fan belt in design.

They each have benefits and drawbacks too. For example, timing chains are often inside a timing cover and are oil soaked. This makes them more reliable and (if they're looked after) means they should almost never have to be changed.

On the other hand, rubber timing belts tend to degrade over time which means that they need to be replaced at a regular interval (usually 4-6 years).

So if a timing chain tends to be more reliable, why are belts still super common?

Simply put, timing chains are a lot more expensive to design and manufacture. Additionally, timing chains are often ridiculously expensive to replace (double or triple some timing belts) and, even though manufacturers try to make them reliable, failures still occur.

Realistically, the best (and really only) time this matters is when you're buying a car as it allows you to weigh up long term costs and reliability.

So what would we choose? Well to be honest it doesn't make a big difference at the end of the day. We love that timing chains should (in theory) last forever and we love that timing belts give us the comfort of a set replacement schedule.


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