Updated: Oct 16, 2021
In this article, we'll be taking a look at timing belts vs timing chains. I will be comparing timing chains with timing belts to see which one is better.
This article will also examine the history of timing belts and chains and how one dominated over the other in different periods of automotive history.
We'll also look at how this influenced the evolution of these components and how it affects you as a car owner.
Table of Contents:
A timing belt or timing chain (also known as a cambelt) is a part of an internal combustion engine.
The timing belt/chain synchronizes the crankshaft rotation and the camshaft to open and close the engine's valves at the correct time during each cylinder stroke.
What Does a Timing Belt or Timing Chain Do?
The task of the timing belt or chain is to maintain the timing of the engine.
By timing, we mean the connection between the pistons, the valves, the crankshaft and the camshaft.
An engine must maintain this timing between critical components at all times.
The crankshaft is physically connected to the camshaft via a belt or chain, and what the belt or chain does is drive pulleys or sprockets.
A belt drives pulleys, and the chain drives sprockets.
Both pulleys and sprockets do the same thing together with the belt or chain.
They maintain the timing of the engine.
A camshaft pulley or sprocket will always have twice as many teeth as the crankshaft pulley or sprocket.
This different number of teeth ensures that the camshaft makes one revolution for every two crankshaft revolutions.
So what's the deal between timing chains vs timing belts?
Both timing belts and timing chains do the same thing.
They use different materials; one is metal the other is a hard rubberish substance.
Other than having different materials using a timing belt or a timing chain has implications for the engine's design.
It also affects the frequency of its maintenance and its durability.
Metal is more robust than rubber, meaning that a metal timing chain is stronger and more durable than a rubber timing belt.
During a typical day of use, an engine will rotate more than a million times, which means that the engine will turn more than 30 million times during a month of service.
Because of an engine's rotational force, the concern here is in the tensile strength of the timing chain or belt.
The concern is how well do chains and belts resist wear.
Chains are the winner because metal resists wear and tear better than rubber does.
But there's a catch.
Metal resists wear better than rubber but only when it's lubricated.
Because metal needs lubrication, this brings us to our first big difference between timing chains and belts.
Timing belts run dry, but timing chains need oil to prevent them from wearing out prematurely.
A chain needs to be sealed away from the environment to prevent oil leaks.
An easy way to tell if your engine has a timing belt or a timing chain is to look in the engine bay.
If the engine has plastic covers, it likely has a belt, but it likely has a timing chain if it has metal covers on the front.
An engine with a chain usually requires a bit more space in the engine bay than an engine with a timing belt.
Because timing chains are more durable than belts, they have a much longer service life.
Some timing chains don't even have a service interval; they last the engine's entire life.
You won't find a timing belt out there that can last the life of the engine.
Even if you don't run the engine, you still have to replace your belt every four to ten years, depending on the car and engine.
You have to replace timing belts because rubber naturally deteriorates with time; even if it's not moving, it will degrade.
Timing belts are also sensitive to oil and coolant spills; this means a leaky engine will wear out its belt much faster than an engine without leaks.
Also, rubber belts don't work well with high temperatures.
Increased temperatures increase the wear of the rubber, and as we all know, ambient temperatures can become very hot in an engine bay.
A typical modern engine has a timing belt service interval of around 60-80,000 miles.
However, in most cars built in the mid-to-late 90s, timing belt materials got a significant upgrade.
In general, timing belts feature a rubber material with reinforcement fibres.
These fibres found in timing belts are usually kevlar or fibreglass, and they increase the tensile strength of the belt.
The rubber itself is usually welded urethane or moulded urethane, or neoprene.
However, in the mid-to-late 90s, rubber timing belts started featuring a material called HSN.
HSN stands for highly saturated nitrile, and this is a material that is pretty resistant to high temperatures.
HSN timing belts significantly increased the service interval for timing belts.
Older engines with timing belts typically had a service interval of around 15-35,000 miles for the belt.
Timing chains, while they do have a service interval around 80-120,000 miles, are usually louder and produce more friction.
Rubber is a lot softer and lighter, which means that rubber timing belts typically run quieter than chains and have less friction.
Timing belts also have less inertia which means it's easier to get them spinning; this reduces parasitic horsepower losses.
Rubber is also excellent at absorbing the vibrations and harmonics of an engine resulting in an engine that feels and sounds smoother.
Types of Timing Belts & Chains
Timing belts usually have a very similar design and don't differ much from each other.
Timing chains come in two different types:
Silent type chains
Roller type chains
Silent Type Chain
The silent chain, as the name suggests, is silent.
The silent type chain reduces the amount of noise generated by the chain and sprocket assembly.
Silent timing chains are pretty standard; you can find them on many engines.
Manufacturers love silent type timing chains because they're cheap and straightforward to manufacture.
A silent chain consists of multiple links held together by pins.
The profile of the links fits the shape of the teeth on the sprockets, which turns the chain.
Roller Type Chain
On the other hand, the roller type chain uses rollers on these pins, and as the chain rotates the sprocket, the rollers rotate on the teeth of the sprocket.
This type of chain reduces friction which is a good thing because it reduces parasitic horsepower losses.
It also reduces localized wear on the chain.
Roller type chains are more expensive compared to silent type chains.
There is another catch when it comes to roller chains; they're a bit noisier than silent chains.
Roller chains also exist in two different types:
Single roller chain
Dual roller chain
The dual roller kind is more robust, more durable, and it's very tough to snap.
However, the dual roller type chain has higher friction and more surface area, which means more parasitic horsepower losses occur.
Another difference between silent type chains and roller type chains is that roller chains are more sensitive to contaminants in engine oil.
The engine oil lubricates timing chains; this is both a strength and a weakness.
It's a strength because lubrication reduces wear, but it's also a weakness because the lubrication of the timing chain is only as good as the engine's oil.
The reason for premature chain stretch and failure is almost always because of one of the following reasons:
The oil wasn't changed in time
The oil was of the wrong viscosity
The oil was of a deficient quality
Any of these three can significantly shorten the timing chain life span and create a chain failure risk.
Roller chains are susceptible to oil that's been in the engine for too long.
Engine oil that has been left for too long and not replaced will have more contaminants.
These contaminants can get stuck between the rollers and the chain's pins, accelerating the wear and tear on the timing chain.
Providing the correct oil is used and its change on time, timing chains are the better option.
After all, a metal chain is more durable is less likely to snap than a rubber belt.
Timing Chains vs Timing Belts History
Back in the 50s and the 60s, all car engines were chain driven; belts didn't exist in that era.
Back then, chains lasted the life of the car.
There are two reasons for this:
Cars didn't cover the miles they do today
Engines weren't as high powered as they are today
A vehicle with 200,000 miles on the clock was a rare sight.
The first engine ever to use a rubber tube belt was a unique racing engine built by Bill Devin in the early 50s.
It used motorcycle cylinders installed on a panelled crankcase.
The engine had an overhead cam layout and horizontally opposed cylinders.
This engine design meant that using a chain was impossible with the technology available in that era.
Hence, Bill used a rubber toothed belt instead, and this car with this engine won the sports car club of the America championship in 1956.
The first-ever, mass-produced car to feature a rubber timing belt driven engine was the West German Glas 1004; it hit the market in 1962.
It had an engine which put out 42hp at 5000rpm.
Leonhard Ischinger designed this new engine; he was a former employee of BMW.
Interestingly, BMW bought Glas in 1966, not because they wanted the cars or the brand, but because they wanted access to the timing belt patents.
1966 was a big year for timing belts.
In 1966, Fiat introduced the first-ever twin-cam engine driven by a rubber timing belt.
In that same year, the US also got their first belt-driven engine in Pontiac's overhead-cam inline-six.
So what do all these timing belt pioneers have in common?
They are all overhead cam engines instead of being a pushrod engine.
The distance between the crankshaft and the camshaft is much greater in an overhead cam engine.
You would need a much longer timing chain to connect the cam to the crank, and with the technology available back then, this meant that using chains and overhead cam engines had inferior results.
Many timing chains on these engines would whip around and rattle.
They had too much slack and wore out too quickly.
Many manufacturers went with timing belts for their overhead cam engines.
However, some good chain-driven overhead cam engines back in the 60s and the 70s did exist, but the number of belt-driven engines on the market started increasing with the number of overhead cam engines.
By mid-1980, timing belt driven engines outnumbered chain driven engines in many parts of the world.
Timing belt dominance continued throughout much of the 1990s and even in the early 2000s in some parts of the world.
But belt driven engines also got some bad rep.
Most belt-driven engines were great and never had any issues with their belts, but some engines snapped a belt even before it was time to replace it.
When this happened on an interference engine, the results were almost always catastrophic for the engine.
When you compare them to the chain-driven engines, which never snapped a chain, they seem like the inferior choice.
Belt-driven engines added maintenance costs and an added risk.
By the mid-2000s, manufacturers started returning to timing chains, mainly because the technology had improved.
New coatings, new heat treatments, and better engineering technology meant that manufacturers could make much better timing chains.
Chains were lighter with reduced friction; they could reduce parasitic horsepower losses.
They could improve the wear resistance of the chains, so many manufacturers switched back to chains for their overhead cam engines.
It was a win-win for customers, they would get the promise of increased durability and lower maintenance costs, and manufacturers would improve sales.
The timing chain was back.
Unfortunately, there was a catch.
Chains of old and chains of new seem to be two different things.
The modern car buyer wants their engine to do pretty much everything; they want power and torque, they want the engine to be quiet and smooth, but they also want good fuel efficiency and low emissions.
Many of these qualities are in direct opposition to each other, making an engine that does it all is almost impossible.
But car manufacturers have to sell cars, so they have to try and please the modern car buyer by attempting to make an engine with all of these qualities.
Many modern engines with timing chains have zero issues.
However, timing chains no longer guarantee the durability and low maintenance costs they used to do in the past.
Sometimes the timing chains on modern engines may even snap.
Timing Belt vs Timing Chain
In summary, the timing chain is more robust and more durable.
However, the timing chain still isn't perfect due to the strain on modern car engines.
In general, a timing belt is quieter and has less vibration, but they also have a higher maintenance cost than timing chains.
Timing belts vs timing chains comes down to a case-by-case basis; each car is different.