EVERYTHING YOU NEED TO KNOW ABOUT YOUR MOUNTAIN BIKE’S CHAIN

It’s a long walk without one

If there is one part on your bike that you really need to pay attention to, it’s your chain. Your bicycle’s chain is the major component of a bike’s transmission that’s responsible for transferring power from your cranks to the rear wheel. With proper care and maintenance, a chain can last a long time. And, with a proper replacement schedule, it’s common to extend the use of your pricey cassette through three chains. Even when you do everything right, although rare, chains can fail. In this “Garage Files” we go over everything you need to know about chains and then some.

PROPER CARE AND FEEDING

The best way to get the most out of your chain is to keep it clean and lubricated. This is a relatively simple process, but here are a few tips. Pick a lube that is best suited for your trail conditions. Dry, sandy to loamy soil typically plays nicely with a dry lube since it penetrates the inner parts of the chain and leaves behind little on the outside for dirt to stick to on the outside. This keeps the chain and contact surfaces with the cogs and chainring cleaner since there is not a wet, sticky lube for dirt to cling to. Wet lube is best for, you guessed it, wet and/or muddy conditions. This lube stays wet at all times, leaving a water-resistant barrier on the outside of the chain. It will attract dirt and grime, so it is much messier than typical dry lubes.

Chain-lube frequency varies greatly and depends on conditions. Here in dry SoCal, we typically lube our chains before every ride unless conditions are perfect, then we can go every two to three rides. Other places with wet or muddy conditions warrant lubing each and every ride.

Most chain-lube instructions recommend degreasing the chain before applying, and this is a good idea if changing lubes or if the chain is excessively dirty. Some chain lubes require stripping all factory grease or lube to work properly. For most riders, the factory-assembly grease is adequate lubrication and should be left alone. The most we would recommend is a brief wipe down of the exterior with a chain lube or solvent soaked rag to prevent dirt from sticking to the grease.

Lubing the chain is simple, but there are techniques for each type. Always start by following the directions on the lubricant container. With most lubes it is best to apply a drop to the junction of each side plate/roller interface as you rotate the cranks backward (on an e-bike, suspend the rear wheel and pedal forwards or rotate the wheel backward). Do this until the inner and outer portions of this junction are wet with lube on the top and bottom of the chain. Some lubes require less to be applied than others so, again, follow the instructions. Then, wipe the chain with a rag, removing excess from the outer surfaces that could attract dirt.

Since most dry lubes rely on some sort of carrying agent to deliver a lubricant deep inside the chain before evaporating, leaving only the lubricant behind, it is often best practice to use dry lubes well before a ride. The day before is ideal, but hours beforehand often can be suitable as well. In a pinch, lubing a chain in need right before a ride is better than nothing.

Wet lube should be applied the same way as dry for moderately wet or mixed conditions with the excess wiped away with a rag. There is typically not a wait time required for wet lubes since they do not contain carrying agents that evaporate. In extreme conditions, like pouring rain or sloppy mud, skip the wipe-down and leave as much lube on the chain as possible. The goal here is to keep as much lubricant on and in the chain as you can before it washes away.

This chain is too short. It looks correct with the suspension extended but chain growth takes up all the slack.

 

MR. CLEAN

A clean chain is a happy chain. Cleaning the chain can be achieved in many different ways. In dry, relatively clean conditions, the act of lubing the chain with a dry lube and wiping it is often all you need to do. Buildup of dirt and lube may require a thorough cleaning a few times a year. Wet lubes, however, tend to make a huge mess and require frequent drivetrain cleaning.

Clamp-on chain cleaners work acceptably well, but a brush with some degreaser can get things just as clean on the bike. Something as simple as Dawn dish-washing liquid and a brush also work extremely well. Excessively messy drivetrains can be removed, degreased and reinstalled. After cleaning, dry the chain with a rag or, better yet, blow the water out with an air compressor. Also, remember to re-lube the chain.

Some quick links like this Shimano one are directional.

 

REPLACEMENT

Chains should be replaced well before they are stretched and worn out, because if left too long, they will take your expensive cassette along with it. As chains wear between the pin and bushings formed into the inner plate, the chain grows in length. It’s a myth that they stretch; they wear. As a chain becomes worn out, the cassette tends to wear with it. Installing a new chain on a worn-out cassette will cause skipping, so will a new cassette paired to a worn chain. These components are best replaced at the same time or well before significant wear occurs. As we mentioned before, replace the chain before it takes out your expensive cassette!

Chain wear will vary greatly depending on conditions, care, mileage and loads placed upon them. E-mountain bikes tend to be harder on chains, and it’s not uncommon to completely wear out a chain in one muddy, rainy race with abrasive soils on any bike. The only way to know if a chain is really worn out is to measure it. Most chain manufacturers say that a chain is worn out when it reaches .75 percent elongation. There are many affordable chain-checker devices on the market that make this so easy that it can (and should) become part of your regular maintenance routine.

Or, you may simply use a ruler to measure the distance between outer pins. When a ruler is laid against a new chain, it will measure 12 inches from center to center of the pins. Any measurement over 12 1/16 inches indicates it should be replaced.

Since quick links are not technically reusable, save the old one for a spare to throw in your hydration pack or toolkit since, they make more than adequate emergency repair parts. Connecting link pins are never reusable, and the chain should not be broken where one was used. As we said before, mileage will vary, but as a general rule of thumb, if we replace the chain before it is worn out, we are able to use three chains before the cassette wears enough to require replacement. A rule to live by: do not put a new chain on a used cassette the day before a big race or ride without testing it thoroughly first. More than one race has been ruined with a brand-new skipping chain due to it not being happy with the worn cassette.

Chain checkers like this Park Tool CC-3.2 make checking for chain wear so easy it should be part of your regular maintenance routine.

 

GET THE RIGHT ONE

Figuring out what chain your bike needs is easy. Simply get a chain that matches the number of gears on your cassette. Even though the modern bicycle chain pitch (distance between pins) has not changed (1/2 inch), the width does change with different speed drivetrains. For a foolproof setup, replace the chain with whatever brand and model you currently have. Most chains are compatible with other brand drivetrains if the speed number matches but not always.

In our experience, chain strength does not vary greatly between models; the low-end chains are typically as strong as the high-end ones. The biggest difference tends to be in the plating and anti-friction coatings of high-end chains. For example, Shimano has SIL-TEC coating (embedded fluorine particles) on its XTR, XT, and SLX chains, while KMC features titanium-nitride carbon coating on its DLC series of chains. Some brand chains are e-mountain bike-rated, while others are not. Fun fact: All Shimano chains are e-bike-compatible.

There are a wide variety of cleaning products that will clean your chain and drivetrain

 

THE CRITICAL MEASUREMENT

All chains need to be cut to the correct length, and the hardest part of replacing a chain is getting that length right. It’s also the thing most novice mechanics get wrong. If you are replacing a chain that is already the correct length, simply lay the new one next to the old one (including the quick links) and cut the new one to the exact same length. Be sure your chain-breaker tool is compatible with your chain. Older chain tools do not often play nice with newer, narrower 12-speed chains. Note that quick links are directional so always install them in the proper orientation. Also, be sure to lock it in place by rotating it above the chainstay between the cassette and chainring. From there, apply the rear brake and rotate the crank forward until you feel it lock into place.

Getting the chain length correct when starting from scratch on a new build is more complicated than replacement. Generally speaking, you want the chain length to put the rear derailleur cage at a 45-degree angle when in the lowest cog/largest chainring combo. The safest way to do this is to follow the manufacturer’s instructions in the manual that comes with your chain and drivetrain. These typically involve wrapping your chain around the largest cog and chainring while bypassing the rear derailleur and adding a set number of links. These formulas vary between drivetrain setups. Furthermore, note that old formulas and rules of thumb do not tend to work on modern 12-speed drivetrains, SRAM has plastic gauges and Shimano places marks on the back side of the derailleur cage to properly make these settings; check the manufacturer’s instructions.

Another thing to keep in mind is that on a full-suspension bike you must let the air out of the shock and bottom the suspension when making these calculations or you run the risk of ripping your rear derailleur off when the suspension compresses and the chainstay length effectively grows. When in doubt, always cut the chain longer since it is much easier and safer to make it shorter than longer. And, always fully bottom your rear suspension while in the lowest gear after installation to double-check your work.

It’s hard to tell by looking, but this cassette is worn out and would likely skip with a
new chain.

 

WHEN IT ALL GOES WRONG

Broken chains are second only to flats as the most common failure out on the trail. Unless you carry a chain tool with you, there is not much you can do about a broken one, so be sure to always have one in your kit. Another item to carry is a quick link or two. Bikepackers and those going out on long adventures should carry a short length of chain for fully functional repairs. Make sure your chain tool and quick links are compatible with your chain from the comfort of home. There is nothing like the surprise of incompatibility out on the trail—and we’ve seen it plenty of times.

When a chain breaks, you will have to remove the damaged portion by driving out the pins. Do this in a manner that leaves exposed inner plates on both ends of the chain so your quick link will connect them. It is important to take into consideration that unless you carry an extra few links of chain and multiple quick links, your chain will be shorter! The best thing to do here is to turn your low limit screw in blocking the last two or three gears on your cassette. This keeps you from mistakenly shifting too far and ripping your derailleur off. Be conservative on your estimates because you also have to factor in suspension compression and chainstay growth.

 

Need chain lube? Check out our chain lube buyer’s guide here: https://mbaction.com/ten-great-chain-lubes-for-your-bike/

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