42. How to Check For Chain Wear

Demonstrates how to measure a worn out chain using Sheldon Brown’s ruler technique.

IMPORTANT: Nuts and bolts on your bike should always be tightened to the manufacturer's specifications.
How to Check For Chain Wear
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One of the most common problems I hear about is chain skip, which is when your pedal slips forward while pedaling under pressure. This is usually either caused by a stiff chain link, worn freehub body, or by a worn chain and freewheel. In this tutorial, we'll learn how to diagnose a worn drivetrain.

Watch the stiff link tutorial first to make sure that isn't your problem. Once you've ruled out a stiff link it's time to check if your chain is actually worn. Chains will 'stretch' over time, because the pins and bushings start to wear, which causes them to start skipping. There are many tools available that measure chain wear (listed to the right of the video), but the easiest and most accurate way to check is by simply using a ruler.

Measure the Chain

With your chain still on the bike, place the ruler's '0' inch mark directly above the center of one of your chain pins. Now count 12 complete links. A complete link equals 1 inner and 1 outer. A rivet on a new chain should line up exactly with the 12 inch mark using this method.

Wear Indicators

According to Sheldon Brown, if the rivet is less than 1/16" past the mark, your chain is ok. If it's between 1/16" and 1/8" past the mark you'll likely need a new chain, but your sprockets should be ok. If it's more than 1/8" past the mark, you'll have to replace both the chain and rear sprockets.

Cassettes & Freewheels

The reason you'd have to replace the rear sprockets is because they generally wear with the chain. While the chain is 'stretching', the gap between the teeth on your sprockets also gets wider and wider. This causes the chain to ride up over the teeth and slip while pedaling under pressure. If you install a new chain on an old sprocket, you'll probably be able to see gaps of light through the teeth as shown. Here's how to replace a cassette or a freewheel.

Front Chainrings

Your front chainrings generally won't need replacing. Because of the larger diameter, the front chainrings usually take twice as long to wear. If worn they are very easy to spot, as they'll start looking like shark teeth. Here's how to replace your chainrings.


Thanks to Sheldon Brown and Cambridge Cycling Campaign for the photos!


Related Links

Discuss this topic in the Chain Forums

10/20 Chain sticks when pack pedaling

I just finished a complete overhaul if the bike. Everything was cleaned, bearings washed and packed in fresh grease.

When I went to live the chain, I noticed that back pedalling causes the chain to stick:


Any ideas?...

08/19 When sitting and riding on mountain bike, front gears will not shift.

Hi, first post, very noobie to bike stuff sorry Smile
(Sorry, it's a little long, tried to keep it concise, sry).

Basically, when the bike is on a stand or even just picking the bike to rear tire is hovering, when pedaling and shifting through the front gears 1,2,3 it shits perfectly. Very smooth and fluid. However, when I'm riding the bike the bike gears will not shift at all!

(Quick necessary back story). Original issue was that the chain was rubbi... Read more >>

08/09 Shifting Problem

My front derailleur is a "Falcon" ---never heard of them! My problem is that I can shift to my large chainring or sprocket but as soon as I let go of the shift lever the derailleur pops the chain right back onto the small ring. W Thanks for your assistance.hen I move the shift lever it "clicks" several times---could there be some type of ratchet that is broken?... Read more >>

08/01 Front derailleur won't shift into third (largest) gear

I have recently been trying to teach myself more about bike maintenance by doing the work myself (I know horrible idea Smile ).  Recently I noticed that my chain was rubbing on my front derailleur so I went and altered the high/low screws on the derailleur.  Initially it wasn't moving when I was fiddling with the screws, and in an instructional video they suggested loosening the nut(bolt?) that holds down the shifting cable to allow the derailleur to reset to it's natural positio... Read more >>

07/17 Front derailleur can't shift from inner chainring to outer...sometimes

So I'm having a very strange problem. I have an old 10 speed Chimo with friction shifters on the stem. A few months back I noticed that when I downshift to the inner chainring, my front derailleur can't shift it back up to the outer chainring. I put it off and only used 5 gears till I tried to fix it today. I flipped the bike upside down and played around with it and it shifted perfectly back and forth. I then righted the bike and had someone hold up the back tire. It also shifted just fine. But when I rode it, once again it refused to shift back up to the outer chainring. Any ideas what this... Read more >>

06/09 Front derailleur drags on middle chainring?

Hi guys -- I'm new to the forum. Thanks for reading.

I'm fixing up a bike I've had for ~15 years that, sadly, I wasn't able to maintain. The bike is an 18-speed Royce Union mountain bike. Aside from new tubes/tires and a new chain, everything else is original (thumb shifters, both derailleurs are Shimano).

The original chain was just too rusted, so I replaced it, and it runs nicely now. Almost. It's fine on the granny chainring, and it's fine on the big ring, but when it's on the middle ring (the one that I tend to use the most), the chain drags across the inside... Read more >>

06/05 Rear derailleur rolling chain off

Hello I recently got my hands on a 99 trek 6000 and I have been working on it in my free time. When I try to ride it the back chain keeps going down in the gears until it pops off the gear on my wheel help!!... Read more >>

05/28 Rear Derailleurs


My rear derailleur is horizontal to the bike frame as opposed to vertical.

I can see no obvious reason for this and am unsure of how to fix it.

The bike was shifting just fine until I literally put it down, picked it back up and went to take off and the rear derailleur had the before mentioned issue.

Any help would be much appreciated....

05/22 7 speed bike / 5 speed shifter handle

So I picked up a newer Schwinn Jaguar off of craigslist for my son.

This is the first bike I've had around in probably 30 years.

The guy I bought it from pointed out that he had replaced the broken stock 7-speed shifter handle with a 5-speed shifter handle. It rides fine and everything else seems to work. The kid wanted it so we brought it home.

I notice that first gear on the shifter is on the third largest sprocket.

Effectively the bike is set up for gears 3-7 at the moment. If I wanted to gear it down is there a way to set it to go from 2-... Read more >>

05/14 Derailleur Spring - how to put it back on?

Hi everyone,

I am very new to bicycle mechanics, trying to get an old mountain bike running better. As I was scrubbing off years of gunk from the chain and derailleur, a piece popped off. I have included pics.



05/05 Remove chain from front derailleur

I got a Shimano tourney front derailleur on my bike. Need to replace it. How to get the chain out?. I hope, I do not have to break a link on the chain. I see a rivet in one end of the metal. I do not see screw or  bolt tightening the two ends.... Read more >>

04/30 Need to press twice to get to lower clog

I followed the instructions in this video
but I still have the same problem on a Shimano Sora race bike.

With the front derailleur, when I want to switch down from a larger clog to a smaller one, I always have to press the shifter twice: the first time moves the derailleur just a little bit and the second time does the job.

Any hint?...

04/09 Change levers to thumb shifters

I have an old 1984 Miyata Model 100
and I plan on replacing the drop handlebar with straight bar.

I'd also like to replace the old lever shifters with thumb shifters on the handlebar. I'm sure this has been done a thousand times but I couldn't find any instructions in this forum.

Any help is appreciated.


[Image: nzri9x.jpg]...

02/29 STI shifter problem

I have one of these old STI shifters from the early 90's


I can shift between the center and small chainwheels, but not from the center up to the big one.
The button goes all the way without resistance.

Any way to fix this or is is screwed for good?

Thanks in advance!...

01/16 Single-speed to 8x geared conversion shifter problem

Hi all
new to the site; I'm sure this is something that has come up before, but I'm currently trying to do a single-speed to 8x geared conversion, with a downtube shifter.
I've got the dropdown hanger for the rear derailleur bolted into the drop-out (after reading advice from this site...thanks!), and the rear derailleur mounted.

The chain runs through the derailleur and smallest gear (and the front cassette) fine, and I've attached the cable into the derailleur OK. The derailleur adjusts position when I use the shifter, but the chain doesn't move with it. I can manual... Read more >>

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