Do you change the oil in your car? Most people will change the oil in their car every 3,000 to 4,000 miles as their manufacturer suggests. Why do they do it? It’s still oil when the mechanic drains it out of the engine right? Isn’t it still lubricating the parts inside the engine? But it is still drained out of the engine and brand new oil is poured in it’s place. The reason that the oil should be changed at a certain mileage is simply preventative maintenance. The engine would continue to run on the same oil for 10’s of thousands of miles, but slowly it would wear out, and the engine would become damaged. This is a much more expensive repair than regular oil changes.
The same is true for the chain on your bicycle. The chain on a bicycle is engaging on the gears in the front and rear. The chain is manufactured with exactly 1/2″ of space between each link, and the gears are precisely manufactured to ‘mesh’ with the chain. The chain is under incredible strain because of the force and leverage that a cyclist applies. The chain is also subject to sand and other road grime that collects and acts as an abrasive, wearing away the metal the chain is made of.
Even with these factors, a chain can last for 10’s of thousands of miles just like the oil in your car. But, over time, the chain will stretch. As the chain begins to stretch and is no longer 1/2″ between each link, it wears the metal from the teeth of the gears to match it’s new length. If a chain is allowed to stretch too far, it will wear all of the gears on the bicycle so much that they will not ‘mesh’ with a new chain. If a new chain is installed at this point, the chain will ‘slip’ on most of the worn gears and create a lot of rumbling noise on the others. Often a customer will come in with a chain that is so far stretched that the bike won’t shift well, or the chain may even be broken. At this point, all of the gears have to be replaced and the repair bill is much greater than it would have been if we had just replaced a chain earlier.
What’s the recommendation? On modern bikes we are seeing people get about 1500 – 2000 miles before a new chain is recommended. On a tandem it’s more like 1000 – 1500 miles. I’ve seen some people get 3000 – 4000 miles with minimal stretch, but that’s the exception. I recommend that you start having your shop check your chain stretch at 1500 miles, and then every 500 miles after that. If you replace your chain at the first sign of stretch it will cost you about $30. If you wait until your rear cogs have to be replaced along with your chain it will run approx. $100. And if you wait until your chain just breaks and all of your gears need replacing it will run from $250 to $400 or more.
How many miles are on your chain?