Chain Care

A worn chain: Cyclists often speak of chain stretch and removing a link or two will fix the problem. This is not true!

Chain Wear & Care

The major cause of chain stretch is wearing away of the metal where the rivet rotates inside the bushing and not the side plates of a chain.

The effect of wear on a roller chain is to increase the pitch (spacing of the links), causing the chain to grow longer. Note that this is due to wear at the pivoting pins and bushes, not from actual stretching of the metal. The sprockets (in particular the larger of the two) suffer a grinding motion that puts a characteristic hook shape into the driven face of the teeth. (This effect is made worse by a chain improperly tensioned, but is unavoidable no matter what care is taken). The worn teeth (and chain) no longer provide smooth transmission of power and this may become evident from noise or chain slipping under load (Cycling uphill or cycling when standing up)

The chain on the left with worn rollers.

Chain wear indicator tool.
Is only used to indicate chain wear before it wears out the chainrings or before it brakes, after that point, it's too late and the tool is not required. 

Chain wear indicator being used.

You can save money by caring for your bicycle between regular servicing. 

Chain wear indicator should be used regularly by the owner or at regular service intervals.

For 7 - 10 speed chains:

If the indicator shows a reading between 0.5 - 0.75 worn, the chain should be replaced soon, before other components also start to wear out fast.

If the indicator shows 0.75 - 1.0 + worn then chain and cassette should be replaced together to avoid wearing out the chainrings.

After replacing just a chain, then performing a road test this would show if the chain runs smoothly on the old cassette as both may need changing, especially where the cyclist only uses one or 2 of their favorate sprockets/gears.

Whether the cassette needs replacing, will depend on how you ride, if you are in the high gear (the smallest cog) all the time. Then this will wear out the teeth on the sprocket and will require replacing the cassette.

Chain wear indicator tool reading: ☺  0    0.2    0.4    0.5    0.75    1.0    1.0 +   ☹
0.75% = 1.59 mm wear per 300 mm of chain length. (1/16" per 12" or/24 links)

"Riding at a bike park where there is sand, then a chain will not last 500 miles"

When to replace the chain:

• Single speed chains replace at 1.0%
• 7 speed to 10 speed chains replace at 0.75% (8 speed chains last up to 2000 miles while 10 speed chains last up to 1600 miles)
• 11 speed chains replace at 0.5%
• Campagnolo say: All Campy chains last between 2,000 - 5,000 miles As to Campagnolo wear check - Campagnolo recommends a chain longer than 132.60 mm (at 6 outer links) the chain must immediately be replaced.

The measurement must be taken in 6 different areas of the chain: if even one measurement is over the foreseen value, the chain must be replaced.

Side Note: Specific eBike chains are available - as there is more torque transmitted from the motor and need to have a higher speck chain. For rear hub motor eBikes, the chain is longer and can wear a lot quicker. As for Shimano 11-speed eBikes, use XTR chains. For Sram 11 speed use X1. And for off-road eBikes replace before 500 miles or risk snapping the chain and/or wearing cassette making an expensive replacement.
(KMC make a 11 speed eBike chain)

To prolong the life of an eBike or x 1 system chain, change 1 gear at a time. Sram now upgrades eBikes to a 1 change at a time shifter.

Having mudguards fitted will help keep the chain clean

Why replace chain and sprockets at the same time?

Both sprockets and chain should be replaced in these cases since a new chain on worn sprockets will not last long and a new chain will eventually start jumping on the worn teeth of the cassette/freewheel.

Worn teeth on the cassette 

Photo shows an 8-speed cassette; cogs 2, 3, 4 & 5 are the gears that are only used and are worn out.
Look close and see they are very pointed like sharks teeth and have a burr on the back edge. (Click on image to enlarge.)

New cassette

Note: Some new bikes are fitted with poor quality parts and when checking a chain for wear, it will show wear at 0.5. KMC chains that are of poor quality will be marked with a "Z" on the chain. All other KMC Chains are high quality and good bike shops will stock KMC chains marked with an "X"

KMC "Z" Chain fitted as standard found on all brands of bikes at the £295 level and below 

Rear Derailleur:

A rear derailleur has two main functions;

1. To move the chain from one sprocket to another.  
2. To keep the chain under tension as you change gear from a large sprocket or chainwheel to a small sprocket or chainwheel. Or you would end up with a chain flopping around.

So as your chain "stretches" the rear derailleur will take up the tension!

Other components that also start to wear out:

If you don't change your chain in time and continue to ride your bike, you won't only need to replace your cassette but also your chainset and jockey wheels often at great expense!

Teeth on jockey wheels worn

These jockey wheels have worn from by riding a bike with a worn chain, from lack of cleaning and lubricating. The teeth will thin and become pointed, especially the lower pulley. Worn pulleys will not be able to hold or guide the chain as well as newer pulleys, and shifting performance will suffer.

Worn teeth on the middle chainring 

The teeth on this chainring are pointed like sharks teeth and hooked by a worn chain. This will also be caused by only using the middle chainring and not changing gear. (A common cause of chainring wear.) Chainrings can be replaced individually, on low-end bikes it normally makes sense as it's cost effective to replace the chainset.  

Worn chain, lifts easy from chainring

Though skipping caused by worn cassette cogs and chain, skipping can occur when chainrings are worn out too. (When the teeth look like sharks teeth)

If your gears have become noisy or the chain is jumping, it is time to have your bicycle serviced/inspected to avoid wearing out your complete drive chain and extra cost.

Tip: When replacing 10 or 11-speed chain & cassette when running a double chainring. Check that the new chain does not stick to the old chainring, due to the alignment of the chain as it will put a burr "an edge" on the teeth of the chainring.
Resulting in wearing out the chainring, it will also require replacing chainring(s)


Lubricating:

Regular lubrication with a suitable chain lubricant is essential and you should also consider replacing the chain on a regular basis to prevent it from wearing out the chainrings as quickly. The cardinal rule for long chain life is never to lubricate a dirty chain, as this washes abrasive particles into the rollers and acts like an abrasive paste. Chains should be cleaned before lubrication. The chain should be wiped dry after the lubricant has had enough time to penetrate the links.

Lubricating a clean chain

Gear Adjustment:

Indexing: If a derailleur is correctly adjusted when it is installed or serviced this is the only adjustment that should have to be tweaked, later on, to accommodate cable stretch.

Gear cable adjustment for 9 & 10 speed rear derailleur every 500 miles. For 11 speed every 400 miles.

Using derailleur gears:

Not using your gears correctly will wear out your sprockets/chainwheel.

Keep pedaling forward. A derailleur leads the chain from one sprocket to another. The chain can only move sideways while it is also moving forward. For this reason, you can only shift while you are pedaling forward. The rear derailleur can usually shift under full load, but it is better for the chain to ease up a bit during the shift.

Even though a bike is "21 speed", it will not have 21 gear ratios with consistent steps between them. You are likely to find that the ratios on the middle chainring are closely duplicated by the gears on the smaller and larger chainrings.

For a "21 speed" bike, you have 3 ranges of 7 gears, NOT 21 gears. The ranges exist to minimize the amount of front derailleur shifting that is required.

Cycle Tech suggests quite sensibly, that you avoid using the "extremes", ie the smallest chainring with the smallest rear sprocket and the largest chainring with the largest sprocket. Using these combinations can lead to premature wear on your chain and sprockets.


Chain technical info 

What else to look out for:

Gear cables:
Are the most common cause of incorrect gear operation. Gear cables can become kinked, corroded and your gear shift will not be smooth adding wear to chain and sprockets. Cycle Tech UK recommends lubricating, inspecting cables regularly and replace once a year. Bike design's and rooting of cables though handle bars and frames is making it much harder to inspect cables for damage and wear, so cables should be changed regular to reduce failure.

 Frayed gear wire   

Rear derailleur:
Before you try to adjust your rear derailleur, you should really make sure it isn't bent. The rear derailleur is the most fragile and exposed part of a bicycle, and they are always getting knocked. Aluminum frame bicycle have a gear hanger to stop damage to the frame, which the derailleur is bolted to.
When a derailleur hanger is bent, it is generally necessary to remove the derailleur to straighten it. Cycle Tech have a special tool, a bar with a sliding gauge on it, that screws into the hole in the hanger in place of the derailleur. This tool provides lots of leverage to straighten the hanger with, and has a gauge to judge when it is parallel to the rear wheel. A rough, on-road repair is sometimes possible by removing the derailleur and bending the tab with an adjustable wrench.

Derailleur Wear: 
The rear and front derailleur will become worn with use and abuse. As the derailleur wears, it will develop play at all pivot points.
For rear derailleur grab the cage at the lower pulley of a new derailleur while mounted to a bike and wiggle it side to side. Replace derailleur when this play becomes significant. Some rear derailleur models allow for servicing and replacement of worn parts.

Wiggle the rear derailleur side to side.

Clean and lubricate rear derailleur, this often improves performance by removing dirt from pivots.

Freehub bodies becoming worn and loose:

Rear end of a freehub body 

The freehub is the ratcheting mechanism attached to the rear hub of most modern derailleur bike hubs. The freehub uses a splined cylinder to hold the cassette cogs. Inside the freehub mechanism will be bearings and a clutch system, usually ratcheting teeth and pawls. The cassette cogs have no moving parts. All moving parts are in the freehub body.

This freehub body is from a 8 month old Specialized bike. The seal that keeps the grease in and the dirt and water out has a poor fitment. As shown in the photo with the seal removed, you can see the ball bearings covered in brown dirt where the grease should be. The freehub was so badly, worn apart from the grinding noise when freewheeling the hub would wobble and would make adjusting gears impossible. Most free hubs can be serviced and sealed bearing type freehubs can have new bearings replaced. This freehub even-though only 8 months old was unavailable and the customer had to buy a new wheel. 

When using your bicycle extreme conditions, service intervals should be at 8 week intervals. Ask your Cycle Tech mechanic about servicing.