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How to Diagnose & Replace Worn Out Bicycle Chains & Cassettes

Repair & Tech Info - Featured Tech Articles

 

Having worked on bikes for decades, the Bikeman knows how to spot  and replace a worn out chain and cassette.  Unfortunately, many cyclists out there are unaware of the benefits of changing one's chain out at regular intervals or how to know when to do it, and finally, how to do the work themselves.  When confronted with a worn chain diagnosis, or even worse, a full on drive train replacement from their local wrench many cyclists react as if they can't believe it.  Chains stretch and wear out cassettes and chain rings my friends and the old saying holds true here - "An ounce of prevention is worth a pound of cure".  Diagnosis & replacement of these common parts is pretty straight forward...lets talk it out. The weak link the bike drive train is the chain and believe it or not, they do stretch over time.  This is normal, the key is changing out the chain before it wears out the much more expensive cassette and chainrings.  The common rule of thumb is a cassette will last you 3 or 4 chains if the chain is changed at proper intervals.  To check your chain for wear you need a chain checker such as the Park CC-2 or CC-3 (click the links to see vids on how they work).


 

The image below is an extreme case but it illustrates a few important points.  1st point being there is such a thing as too much lube, 2nd being regular maintenance is a good idea.  The main thing we can glean from this image is what a worn cassette looks like.  See the way the 2nd and 3rd cogs look, kinda of pointy.  It's totally worn out and definitely prone to skipping under power.  Then look at the bigger cogs outside of the chain, see how they have a nice round profile to the hollow where the chain goes and square tops to the teeth.  Much better, although they could still be prone to skippage because the chain must be super stretched to have worn out the smaller cogs as badly as it did.  In order for a cassette to be worn out this unevenly the rider is obviously riding in the same gear(s) all the time and is pretty atypical.  This guy obviously needed both a new chain and cassette, your case might not be so cut and dry.  Sometimes you slap on a just new chain to replace a moderately stretched one and it's fine, no skippage under power.  Sometimes just a chain won't do and a new cassette is needed as well, you won't know until you try it. If it's questionable, just do the cassette too, you won't regret it...new drive trains feel awesome!

 

 

So, let's assume you've measured your chain and it's just worn enough to replace without needing a new cassette.  Well, you'll need a new chain (call if you're not 100% sure about which chain is for you, there are a lot of variables, particularly 10 & 11 speed),  a chain tool (we recommend getting at least the Park CT-5), about 30 minutes, and this article on correct chain sizing.  For what it's worth, SRAM chains are typically less expensive and come with a "power link" enabling tool free removal for cleaning, overhauls, etc.

Or maybe it's time to change both.  You'll need the right cassette, which we explain in this related article, a chain whip, cassette lock ring tool (most likely the Park FR-5GC), a big adjustable wrench, some grease, about 45 minutes, this quick little video on how to remove and install a cassette...and maybe a beer.

Now the trick is to make sure you check your chain at regular intervals to keep more of your hard earned $ in your pocket and your bike running optimally.  Give us a call @ 1-800-BIKEMAN if you have any questions, we love talking bikes!

 

Here are some links to the essential parts and tools to change out your own chain and cassette on Bikeman.com

Cassettes

Chains

Tools

Google

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