Mountain Bike Maintenance

Chains

Posted by SteveUK MTB on March 18th, 2008

Chains

MTB chains come in two basic sizes, 7/8 speed or 9 speed. 9 speed chains are narrower (up to 6.8mm) than a chain for a 7 or 8 speed (up to 7.2mm). This means that it’s possible to use a 9 speed chain on a 7/8 speed cassette, but the spacing of sprockets on a 9 speed cassette is too close to allow a 7/8 speed chain.

The length of your chain is determined by the size of your bike’s largest gears. The chain needs to be measured so that it goes around the largest front ring and the largest rear sprocket, missing out the rear derailleur, with two (one inner, one outer) links to spare. How to cut a chain is described a little further down the page.

If you’re running a single chainring set-up (ie 1×8 or 1×9), you should try going with +4 links.

Shimano, SRAM, KMC and Connex (Wipperman) are the main manufacturers. For 9 speed, the Shimano XTR/DuraAce (CN7701) is generally considered the benchmark as it is strong, durable and contributes to clean shifting.

Chain wear is dependent on many factors (lube type, conditions, environment), including, of course, how smoothly a rider changes gear (ie. not under full pedal pressure).

Chain wear, which is also know as ’stretch’, occurs as the rollers become worn (see the top-left picture below; the left-hand roller is new, the right-hand roller has a ridge along the center of the interior surface which will correspond with the space between the two halves of the inner link plates), plate interiors and, most importantly, the pins (top-middle picture), effectively increasing the overall length of the chain.

The ‘working’ points of your sprocket and chainring teeth are a specific distance apart, which should match up to the distance between the rollers of the chain. As a chain wears, the distance between the rollers is increased. If the distance between the rollers increases by more than 1% of the original distance, the chain will begin to wear away at the teeth on your gears. Typically, your chain will wear first, then your rear sprockets followed by the front rings. Although a chain and gears used from new may operate well beyond 1% before the chain begins to slip off the gear teeth, once a sprocket is worn away beyond 1% it may not accept a new chain without slipping occurring so the gears must also be replaced. Manufacturers may specify their own limits, but growth of 0.75% can be taken as a good measure to replace your chain with the assurance that your gears will still be relatively unworn. Remember that wear will accelerate as the pins and links deteriorate.

The tool in the top-right picture above is a Park Tool CC-3 and could represent the best £/$6 you’ll spend on your bike. It’s an absolute doddle to use, taking literally seconds to confirm the condition of your chain, and could potentially save you a lot of money. The difference in cost between a new chain and the cost of a new chain plus a cassette and new set of chainrings or a crankset is almost certainly going to run into triple figures. Buy a chain checker and use it regularly. So, we’ll move on to getting the chain out of the drivetrain. For those of you who aren’t using a SRAM Powerlink or KMC Missing Link, you’ll need to split the chain by pressing out one of the connecting pins. It is possible to re-use the pin on 7 and 8 speed chains, although Shimano recommend, as would I, re-joining all of their chains by using new, reinforced connecting pin (variations shown on chart below). 9 speed chains must always be closed using a new pin. Anyway, splitting a chain is pretty much the same across the board, with chain tools coming in all shapes and sizes, but basically doing the same thing. The one in the pictures is a Newton tool that I removed from one of their multi-tools.

To open, simply take a section of chain in each hand so that there is no pressure on the link and push the two halves together across the length of the chain so that each pin protrudes from the smaller section of the hole in the plate (left-hand picture). Now slide the pins towards each other until they are in the larger section of the hole (middle picture), enabling you to separate the two pieces and break the chain. Simple, eh?

Refitting is the opposite of removal; just make sure to ensure that both pins are sliding onto the ridge on each plate. It can take a little practice to be able to hold on to each end of the chain while trying to line everything up, but how quickly you do it really is just a matter of practice.

Powerlink/Missing Link

Opening the SRAM Powerlink or KMC’s Missing Link is straightforward;

Pinch the opposite sides of the link together…

… push the chains pins towards each other to open the link…

… the chain can now be opened…  Easy as 1, 2, 3…

Chain Lubrication and Cleaning

“Chains are like underwear; change often and keep them clean” - some sage advice from MTBR member 23mjm.

There is a misconception that a “well lubed” drivetrain means that there is lots of lube on the chain, cassette and rings. The idea being that less wear will occur on moving metal parts because they have plenty of lubrication. Well, if the drivetrain was enclosed in a sealed box, as it is in most motor vehicles, this would certainly make sense. However, your bicycle drivetrain is entirely exposed to the environment that you ride through, dust, grit, water and all, so the truth is that the only lube that is useful is that which works between the inside of each roller (bearing), the plate/pin on which it sits and the areas where the inner and outer plates overlap. The external surface of the roller, the cassette sprockets, derailleur jockey wheels and the chainrings should all be as clean as possible. Any lube on these components will only serve to attract the dirt that will contribute to reduced shifting performance and the accelerated wear of the drivetrain.

It’s a contentious issue, I know, so what you’re about to read can be taken with however large a pinch of salt you like. It is my opinion that a bicycle chain can not be adequately cleaned and relubed if it remains on the bike. Chain cleaning machines do more harm than good as they douse the entire drivetrain in degreaser which needs to be washed away (all over the rest of the surrounding area) with water. Degreaser in such quantities is impossible to remove from the chain in particular, but also the cassette, no matter how long you spend rinsing and wiping, so will make redundant any fresh lube you apply afterwards. You also run the risk of degreaser/water working its way into hub or freehub bearings. It is for these reasons that I will always only recommend complete removal of a chain for cleaning.

On we go then, to the cause of much mechanical procrastination, argument and mud-slinging; the cleaning of the bicycle chain. There is much discussion about the ‘best’ way to clean a chain, and many products and systems all claiming to do it better than the other. I’ve tried the mechanical chain cleaners, various cleaners and degreasers and have come to settle for White Spirits, or Mineral Spirits as I believe it’s called in the US. My basic method is as follows;

  • Drop the chain into a jar 1/3 filled with spirits (doesn’t matter too much how dirty this stuff is) or your chosen degreaser and shake steadily for a couple minutes.
  • If you have the time, you could leave the chain to soak for 20 or 30minutes before giving the jar another shake.
  • Remove the chain and drop into a second container (I use a plastic flask with screw-on lid) with bike cleaner or washing-up detergent and some hot water. Shake well for a minute or so and then pour the dirty stuff away.
  • Fill the container up with more hot water and shake to rinse, emptying and repeating until the water is clear of dirt. Wiping along the chain with a cloth will give an indication of how much dirt is left between the links. There’s nothing to stop you going back and doing another shake in the spirits jar before repeating the soap and hot water rinsing process.
  • Dry the chain as best you can with a cloth or tissue paper. If you have access to compressed air, even the canned type, blast any stubborn water out of the links. Blowing hard works pretty well, too. Because you’ve used hot water the chain should be almost entirely dry by now. Just to be sure, put it in the sun or on a radiator and leave to dry, wiping occasionally to rotate the rollers and help any stuck water out of the chain.

(White spirits can be filtered through coffee percolator-type paper filters and re-used.)

There is an increase in popularity of ultrasonic baths for cleaning bicycle components, and chains in particular. These devices cost from around $20-30 for a small unit and are an excellent way to save you some time in your maintenance schedule. Typically, they’ll use a water/detergent fluid, although it is possible to get specific fluids for use in ultrasonic baths. Some people have achieved good results using mineral spirits or degreaser. I use water with a couple of teaspoons of dishwashing detergent in mine after giving the chain an initial soak and shake in a jar of mineral spirits.

There are many chain lubes to choose from and everyone has their favourite. I’m using Purple Extreme at the moment and finding it to be an excellent product in both wet and dry weather, a real advantage here in the UK where the weather and conditions can be so unpredictable. One potential disadvantage to Purple Extreme is that it is best left for a while (manufacturer recommends over night) before riding a freshly lubed chain. I’ve turned this into an advantage by buying a second chain which can be cleaned, dried, lubed and left until needed. Now, when one chain requires cleaning or relubing, I have a ‘ride ready’ chain waiting to go straight on. There are other advantages to this method; one is that I’m never in a rush to clean and lube a chain and another is that pretty much all of the ‘wet’ solvent from the lube has dried off long before I throw a fresh chain on my bike. This means that the chain, jockey wheels, cassette and chainring run as dry as possible, and thus pick up a minimal amount of muck. Here’s my method for application of Purple Extreme…

I’m sure that this method, or variations of it, will work just as well with most of the fluid (ie. non-wax) based lubes.

Whichever lube you decide to use, try to make your choice based on the conditions you’re riding in; you may have to use different products at different times of the year. Whatever you choose, you’ll invariably find that following the manufacturers’ instructions will yield the best results. I alternate between two chains; not only does it seem to prolong the life of both chains and sprockets, but it also means that I’ll always have a clean/lubed chain to throw on. I strongly recommend checking the MTBR reviews for specific lubes, finding out what other local riders use and, most importantly, trying out as many as possible for yourself. Again, following the manufacturer’s instruction will usually yield the best results.

Back to main guide…