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Chain life, the lies, the truth

When to replace your chain? Do chains stretch? What’s an in spec chain? How do you get more life from your chain? and other techy chain questions addressed.

Why an “in spec” chain is good a thing

There are a lot of myths around chains and drivetrain components, one thing we know for sure is that an “in spec” chain will help with many aspects of riding your bike. Better gear shifts, nice ride feel and less unneeded money spent on your bike in the long run (we will get into this later).

What is a “out of spec” chain?

Chains are made from moving small steel pieces, they accumulate a lot of grit and road grime and they rub against other metal parts. This sandpaper like friction causes the chain to wear down.
When a chain wears beyond a certain point it no longer fits accurately with the other parts on your bike and performance degrades. In bad cases of wear it can cause skipping gears and other troubles.

How long before a chain is worn?

Think of a chain as a consumable item, if you don’t have a chain checker, a general rule of thumb they need to be replaced around every 2000 miles, this is akin to the oil in your car. For most commuter riders that means replacing a chain every 8 or 9 months. For higher mileage riders that can mean every 4 months if you are drilling hard on it and racking-up miles.

Problems with a worn out chain

Like a lot of things with bikes, the issue is technical. The chain is often made from the hardest material when compared with the other drivetrain parts. Most chains are made from special hardened steels, most other parts that the chain comes in contact with are made from softer aluminium (chainwheels, some cassettes) and a form of nylon (pulley wheels in your derailleur). These other materials are physically softer and the chain’s hardened steel will wear them away.

In short, When the chain is “out of spec” it will quickly wear the other components to “out of spec” status also. And parts will not mesh well together, thus problems arise.

How do chains stretch when they are made of strong steel?

Someone once told me that chains stretch, it’s a common thing I hear, maybe it’s because it’s easy to say without explaining. Technically, chains don’t stretch they wear and cause the overall length to get longer. (it would take a lot more force than a cyclist to actually stretch the steel plates 🙂 ) The small parts, pins and rollers within the chain design naturally wear down and the net impact is it becomes longer by small yet important amounts. As the chain gets longer it get to a point where it becomes “out of spec” and progressively out of “mesh” with other drivetrain components. At this point it starts a hyper accelerated process of wear on these non chain parts.

The bad news (why you should change out your chain)

Often I see riders with very worn out chains, vastly out of spec. These riders will see issues with skipping gears, high resistance & difficulty changing gears along with crunchy noises when pedaling.
At this point more than likely the chain has been out of spec for a while and it has damaged other parts of the drive train. To get the bike back to a place where the gears shift good, and no longer feels crunchy and be expensive.

Take a mid level gravel bike with shifting problems in part due to a very worn chain. This will mean replacement of the following:

Repair bill:

  • Cassette (gears in the back) – $55 upwards
  • Pulleys – $20
  • Possibly the Chainwheels (gears in the front) – $120 – approx
  • Plus the cost of the new chain – $35

$230 in parts cost alone, no labor cost

On the other hand replacing the $35 chain just before its worn / out of spec can make the other parts of the drivetrain last many years.

The Good News or What can you do?

Obviously the biggest thing is change your chain when it is worn out of spec, it’s pretty easy to do or if you have a bike shop do it, they can check to see if your current one is worn and replace its a 15min job and $10 in labor, well worth it as they will size the chain for proper use. (sizing chain requires special tools) and they will recycle your old chain for free.

You can make your chain last longer – The biggest accelerator of wear is dirt. Dirt sticks to the chain lubrication from normal riding and acts like sandpaper in the internal of the chain and the rest of your gears and drivetrain. A daily or weekly routine of wiping the chain to remove loose dirt / grime with a rag and lightly using some high quality chain oil will prolong the life of your bike parts.

Tip 1 – Have a rag handy where you park / store your bike, to make it an easy habit forming thing.

If you chain is really dirt, caked in mud and gunk its best to give it a proper cleaning. A rag, some simple degreaser and some fresh chain oil will do the trick.

Tip 2 – Check your own chain – Buy a handy chain checker tool from your local bike shop or online. Keep it with your chain rag and lube, this will save you from estimating. I like this one, its simple to use, accurate and doesn’t break the bank around $16. (I prefer it over the clicker type Park tool which can give inaccurate results). This one simply drops in and makes a measurement, telling you when to replace the chain.

Measuring chain wear or elongation on a Shimano CN701 Chain with a Prolink Chain Gauge. Here showing the gain at 5. Replace at 8 or 9 for best results.

Tip 3 – When you buy a new chain, buy a couple. Having a spare chain on hand will give you less excuses to swap it out and you might even get a better deal on buying 2 or 3 chains. 🙂


More Info:

Above is an example of a KMC chain checker in use, the Prolink one works the same way but indicates a level of wear vs the KMC Go / no go method.

One reply on “Chain life, the lies, the truth”

I have few chains and after about 500km (some people prefer 1000km) I change chain with one from my chain set. Of course I choose shortest chain. It should extend lifetime of chains and general bike drive set.

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