When Should I Replace My Bike Chain?

By : Mr Mamil
Updated :

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One of the most commonly asked questions among cyclists is,

When do I replace my road bike chain?

While it sounds like a straightforward question, unfortunately, there isn’t an exact answer. There have been plenty of debates among cyclists over the years. Ask 10 cyclists, and you’d probably end up with 10 different answers. If you ask your local bike shops, you might get various answers to the same question.

A quick look at some leading brands and you’ll quickly notice that their recommendations of when to replace the chain aren’t consistent with each other either.

Basics of a chain wear

Use Park Tool CC-2 Chain Checker
Use Park Tool CC-2 Chain Checker

As you ride, each part of the chain experienced a huge amount of friction, which is why using the right chain lube is important. The constant rubbing between the chain and cassette/chainring causes the pitch (length) between each link to grow.

A standard pitch for a new chain is ½” (12.7mm), which makes it 1” (25.4mm) if measured from the inner to the outer plates. Chainring and cassettes are designed with this ½” pitch in mind for the chain to sit firmly at the base of the cassette/chainring.

With each contact with the cog, the inner plates move around the riveted pins. Over time, the inner plate’s bores expand, which leads to some play between these pieces. And if you consider there are 110 to 114 links on a properly set up chain, the chain stretch can be noticeable.

When the chain stretches (wears out), it will sit higher up the cog/chainring teeth, causing them to wear out quicker. If not replaced, the chain will eventually sit higher up the cog/chainring teeth, and you’ll get the dreaded chain skip when you put power to the pedals.

Bike mechanics face this almost every day, and you’ll often hear advising cyclists to replace the chain before it starts to wear out the cassette and chainrings. These usually cost much more than a chain, so it makes sense to try to prolong their lifespan.

A new $40 chain will go a long way in saving you hundreds of dollars in prolonging the lifespan of the cassette and chainrings.

What affects chain wear?

The common factors that affect chain wear are :

  • Riding style. A lower cadence will result in a higher wear rate due to the higher torque.
  • Chain lubes. Avoid dry chain lubes if durability is the key concern. For many, waxing the chain is the gold standard.
  • Riding conditions. Wet and muddy conditions are the worst conditions to ride in.
  • Shifting habits. More shifting = more wear due to increased metal-to-metal contact.
  • Terrains. A hillier terrain generally requires more power/strength, which will wear out the chain faster.
  • Regular cleaning. A clean drivetrain can last longer.

With that said, it’s not recommended to gauge your chain wear just by tracking the mileage done. A chain that did 1,000km in the flats will have significantly lesser wear than 1,000km in the mountains.

Interesting fact : The pros have their chains replaced around the 1,000km mark in the Tour de France especially during the third week where most of the mountain stages are held.

Manufacturers’ recommendations

Manufacturer

  • Park Tool – 0.75% for 10s and 0.5% for 11s (and upwards) chains
  • SRAM – 0.8% for 11s, 12s chains
  • Shimano – 0.5% to 0.75%
  • KMC – 1%

One similarity among them is to replace the chain starting at 0.5% elongation (stretch).

Let’s put this into perspective. A new chain will typically have around 0.25% stretch, and most cyclists replace their chain anywhere between 0.5% (recommended) to 1% stretch (not recommended).

Many factors affect chain wear which I will discuss further below. One thing that you should know is not to replace your chains based on the mileage done. Instead, use a chain checker to accurately quantify the amount of chain wear.

“It is difficult to pin down an exact number to kilometres due to the fact that riders come in different weights and sizes, ride differently, shift more or less frequently, develop more or less wattage, ride on flat or hilly terrain, clean or nasty conditions, take care or leave their chain dirty… all of which create large variables in just how much wear and tear is created,”

Joshua Riddle, Campagnolo

“For chain replacement, we do not state ‘every x kms’ as this is not possible. Chain wear is based on multiple factors including maintenance (clean/lube), use conditions (water/mud/sand), user shifting patterns, and overall drivetrain condition (cassette/ chainring wear).”

SRAM