Bike Chains, Part 2

Table of Contents

Preliminary

Revised

This is Part 2 of a series of 9 posts organized as a single article. There are 8 parts, individually published as posts on this blog, and a table of contents of the series in the 9th post. The series is organized into sections, numbered for reference, in the series table of contents and in the table of contents for each post. In March 2024 I began to reorganize and revise the long article. The project took several months.

Scope

This post mainly discusses the bicycle chain, an adaptation of industrial roller chain technology, usually made of steel 1an alloy of iron and small amounts of carbon and of other metals, made by melting mineral ores in furnaces.

The chain is a part of a group of components called the drive train, which takes force from the rider’s effort pushing down on the pedals, and turns it into force driving the drive wheel to rotate which pushes the bike. The drive train includes the pedals, the crank arms, the chain wheels, the chain, the rear hub, the cassette of gear wheels on the drive wheel (normally the rear wheel) and the derailleur mechanisms. The drive train must be aligned properly, maintained, cleaned and lubricated to operate efficiently.

Chains are vulnerable to wear if and when they allow contaminated oil and water to carry microscopic abrasive particles into spaces that are supposed to be clean and lubricated. Chain wear elongates a chain, which affects performance and causes damage to other drive train components. Lack of lubrication or contamination of bearings in other drive train components (e.g. hubs, jockey pulleys) can affect performance.

A few new or modern bikes have bushed chain. Many new bikes have flexible bushingless chains. Bushingless chains may be more prone to this than bushed chains, and chains that maintain a direct chainline.

Bicycle chains can break. Usually this happens when a chain comes off the cogs – commonly during shifts with derailleurs – and is caught between components. In this situation the chain is seized, and the rider is applying force to links that are not traveling in the normal direction of travel.

4. Chain Drive

Industrial chain drives

The manufacturing and maintenance of roller chains, bicycles and lubricants was based on trial and error, experimentation and the concepts used by artisans, mechanics, engineers and riders. Chain drives were used in industrial machines before they were adopted by the bike industry late in the 19th century. Chain drives are designed for classes of machine, in some instances, for individual machines. A bicycle chain is made of links connected by pins in a continuous loop. The links must pivot rapidly at the pins as the links move in the loop.

Until modern optics and electronics provided better tools, people affected by wear had theories or mental models for what happens in a lubricated roller chain. With modern optics and electronics it is possible to view components of stationary disassembled chains. Josh Poertner of Silca Velo 2noted in the post Part 4 in this series discusses chain wear as the cause of elongation in the video on the Silca Velo YouTube channel Microscopic Magic: Save Your Chain from Wearing Out! (July 30, 2024).

Bushed Roller Chain

The links in a bicycle chain drive overlap, alternating as inner and outer. Links are made of plates and “pins”. Plates form alternating outer and inner links. Pins attached to the outside plates; the pins also fit into holes in adjacent inner links. Hollow pins made of tubular steel are common. The pins are riveted to the outer plates. The pins connect the links to adjacent links; the links pivot on the pins. On modern chains these are tubular rivets flared at each end, installed as flush rivets. Tubular “bushings” between the inner link plates keep the inner links of a bushed chain separate. The half bushings of a bushingless chain (see below) have the same effect.

Rollers were a late 19th century industrial innovation, adopted by bicycle and component builders when chain drives were adapted for bicycles. Rollers contact the cogs (teeth”) of the gears from which and to which force is transmitted. Rollers are the journals of plain bearings. (the bushing and/or the pins rotate inside the rollers. A chain drive has several dozen open plain bearings. In a bushed chain, rollers revolve on bushings around the “pins” holding the sides of the roller chain together. On a bushingless chain, the bushings are stamped shapes on the inner plates. Most bicycle drive trains from the late 1890s until the 1970s or 1980s were have been chain drives using “bushed” roller chains. Wikipedia notes:

There are … many chains that have to operate in dirty conditions,
and for size or operational reasons cannot be sealed. Examples include chains on farm equipment, bicycles, and chain saws. These chains will necessarily have relatively high rates of wear.

Many oil-based lubricants attract dirt and other particles, eventually forming an abrasive paste that will compound wear on chains. This problem can be reduced by use of a “dry” PTFE spray, which forms a solid film after application and repels both particles and moisture

Wikipedia, Roller Chain

Bushed bicycle roller chain, invented by the Swiss-English entrepreneur Hans Renold in 1880, was common on the bicycles made in the late 19th century, and on single speed and utility bicycles manufactured and sold in the first several decades of the 20th century. The invention of bush roller chain has been attibuted to others:

… the Nevoigt brothers, of the German Diamant Bicycle Company, designed the roller chain in 1898 which uses bushings.

There are two types of links alternating in the bush roller chain. The first type is inner links, having two inner plates held together by two sleeves or bushings upon which rotate two rollers. Inner links alternate with the second type, the outer links, consisting of two outer plates held together by pins passing through the bushings of the inner links. The “bushingless” roller chain is similar in operation though not in construction; instead of separate bushings or sleeves holding the inner plates together, the plate has a tube stamped into it protruding from the hole which serves the same purpose. This has the advantage of removing one step in assembly of the chain.

The roller chain design reduces friction compared to simpler designs, resulting in higher efficiency and less wear. The original power transmission chain varieties lacked rollers and bushings, with both the inner and outer plates held by pins which directly contacted the sprocket teeth; however this configuration exhibited extremely rapid wear of both the sprocket teeth, and the plates where they pivoted on the pins. This problem was partially solved by the development of bushed chains, with the pins holding the outer plates passing through bushings or sleeves connecting the inner plates. This distributed the wear over a greater area; however the teeth of the sprockets still wore more rapidly than is desirable, from the sliding friction against the bushings. The addition of rollers surrounding the bushing sleeves of the chain and provided rolling contact with the teeth of the sprockets resulting in excellent resistance to wear of both sprockets and chain as well. There is even very low friction, as long as the chain is sufficiently lubricated. Continuous, clean, lubrication of roller chains is of primary importance for efficient operation as well as correct tensioning.

Wikipedia on Roller chain, July 2021

Bushed chain is being used for some e-bikes, and some mass-produced bikes without derailleurs, as of 2021-24. On a bushed roller chain the rollers rotate on bushings around pins.

Plain bearings need lubrication, according to the experience and opinions of builders, engineers, and mechanics and riders/users. Lubrication reduces the co-efficient of friction when steel surfaces in contact with each other:

Lubrication is required for correct operation of mechanical systems such as pistons, pumps, cams, bearings, turbines, gears, roller chains, cutting tools etc. where without lubrication the pressure between the surfaces in close proximity would generate enough heat for rapid surface damage … .

Wikipedia on Lubrication

If lubrication is applied often enough, and if the chain is properly cleaned and maintained, rotational friction and chain wear are reduced. On a bicycle chain, the lubrication is directed at reducing the friction of the rotation of the rollers on the bushings, and the bushing on the pins. When the lubrication fails, the rotation fails, and the direction of friction become intermittently linear which produces audible squeaks as the chain metal of the bushing and the pin wears.

“Factory lubrication” of bike chains by the chain manufacturers seems to have become a common practice when bushed roller chains were common.

Parts 3 and 4 this series, on lubrication, lubricants, and testing, will discuss the researched and tested fact that oil based lubricants work by creating a film across metal surfaces, and how lubricants behave when contaminated with water and dirt.

Material & Manufacturing

Chain link plates for modern bike chains are punched out of steel sheet metal made with carbon steel. Steel is an alloy of iron, carbon, and other elements. Carbon steel is more susceptible to oxidation (rust), corrosion and wear than other steels. Chromium makes steel harder and more resistant to oxidation and wear. Alloys harder or more resistant to corrosion than carbon steel would cost more and would require retooling by the chain manufacturers. On some chains link plates and other chain parts are plated with metal less susceptible to corrosion, or case hardened.

Adam Kerin of Zero Friction Cycling provides 3mentioned and discussed in Part # 4 in this series an overview of materials at pp. 9-11 of his chain longevity testing brief:

The most common hardness ratings are Rockwell D and Vickers.

… the Vickers hardness test is generally regarded as the most suitable. Mild steel/stainless steel will typically have a Vickers hardness rating of around 150 to 200. Quality hardened steel will be 200 to 400, or even 500, and the highest level tool steels / high speed steels can be up to 700.

However – the harder you make steel, the less ductile and more brittle it becomes. Steel can be made with very high “toughness” – combination of hardness and ductility – but this is very expensive requiring alloying with multiple other metals plus quite exacting heating/cooling cycles. For bicycle chains … different manufacturers use a different level or grade of steel. Campagnolo for instance claim their chains are made of “special steel”. What grade of steel is used is unlikely to be advertised or even disclosed by manufacturers. But in summary for bicycle chains, you can expect the steel will be hardened for wear longevity but there is limit as to how hard they can make this steel without the chain becoming too brittle and snapping on the first poor shift – especially the more economical grade of steel that is used.

Adam Kerin, Zero Friction Cycling site, Chain longevity testing brief, 2018

There is no industry standard for the necessary hardness and tensile strength of the steel. Chain manufacturers order sheet steel by thickness – they trust the steel mills to supply steel that meets the chain maker’s specified standards. Chain manufacturers will market some chains as having been hardened more and better, or coated. Some chains are better than others. Bike manufacturers and bike shops disclose the name of the chain manufacturer; a high value chain may be a marketing point. Even cheap chains work for hundreds of hours.

Modern chains are as light as feasible. Some materials and manufacturing methods make some chains last longer than others in a perceptible way. Some of the issues will be discussed in Part 6 in this series, on durability

Bicycle manufacturers acquire chains (supplied with new bikes) from specialty manufacturers including Renold, Campagnolo, Rohloff, Wipperman, Shimano, YBN, KMC, SRAM and others. Some chains are still manufactured by German, French, English and Italian firms. A few chains are made in Japan. Bike chain manufacturing in 2022 (and 2023 and 2024) is largely an Asian industry. The manufacturers all make chains out of the same raw stocks, but have different suppliers, machinery and workforces. Some chain manufacturers subcontract to each other. A few chains are made in Europe and the US. (The packages of chain sold by the US brand SRAM indicates those chains are manufactured, or at least assembled and packaged, in Portugal).

The Japanese firm Shimano is a dominant force in manufacturing bicycle components, including cranks, derailleurs, and chains. It outsources a portion of production of its branded chains to manufacturers in Asia, e.g. KMC of Taiwan or YBN, a Taiwanese firm that makes chains in a plant in Vietnam. SRAM brand chains are manufactured in Portugal. Many European manufacturers have subcontracted to Asian firms or built Asian plants.As of the early years of the 2020s, most chains are manufactured in Asia.

Many chains are made in Taiwan, the People’s Republic of China and other Asian countries with steel, and other industrial supplies and with manufacturing capabilities. The steel in chains machined in Asia will normally have been sourced from Asian foundries – it will have been smelted and forged from iron ore and carbon, rather than from recycled steel. Pins are steel too. The pins are fabricated from steel stock according to the methods used by manufacturers. The steel mills decide how to forge, roll and process the steel. The chain manufacturer can choose the thickness and some of the performance characteristics of the steel. The options depend on what the steel manufacturers are selling, and price. The shortage or unavailability of chains for purchase in 2020. 2021 and 2022 was attributed to delays in production and transportation of materials.

Bushingless Chains

The bushingless chain was developed by Sachs under the Sedis brand and introduced in 1981. It was adopted by SRAM, which was a mountain bike component manufacturer at that time. The innovation was widely adopted by other designers and manufacturers:

More recently, the “bushingless roller chain” design has superseded the bushed chain. This design incorporates the bearing surface of the bushing into the inner side plate, with each plate creating half of the bushing. This reduces the number of parts needed to assemble the chain and reduces cost. The chain is also more flexible sideways, which is needed for modern derailleur gearing, because the chainline is not always straight in all gear selections.

Wikipedia article on Bicycle Chain

The holes in outer link plates are smaller than the holes in inner link plates. The holes in inner link plates are punched to create the protruding shoulders which serve as partial or “half” bushings. The lateral flexibility of chains (necessary for shifting to different gear wheels or cogs) was engineered by swaging (shaping the pins into barrels rather than perfect cylinders).

The side plates of the inner links are formed into half bushings or shoulders. The roller rides on the half bushings. The pins go through holes in the outer side plates and the half bushings and hold the links together. The outer plates overlap and turn against the inner plates. The plates turn on the pins where the pins go through the plates. My photo of an outer and inner link (left over after I had shortened my new bushingless SRAM chain for installation) shows these features. The hollow pins used in this chain connect the outer links – an outer link on the left. The pin on the left is still partially displaced by the chain breaker tool (there is no roller on that pin – the roller stayed in inner link which was used to close the chain with a master link). The inner link on the right has been pried open to release its roller and show the bevels. The (small) magnification of my smart phone camera shows what the surface, which appears to be perfectly smooth and shiny, are actually rougher. The roughness does not affect the travel of the chain over the cogs. Lubrication is supposed to affect the articulation of the plates, rollers and pins at the ends of the links.

Modern bushingless chain is more vulnerable to wear than other designs:

The inner side plates of a bushingless chain are three-dimensional. Instead of having a simple hole at each end with a bushing pressed through it, each inner side plate hole has a protruding shoulder that amounts to half of a bushing. Since the side plates have an inside and an outside determined by the existence of the shoulders, they can also have bevels on the inside edges without further complicating the manufacturing process. These bevels permit the chain to run more smoothly when it is not perfectly lined up with the sprocket than a conventional chain with flat inner plates. They probably also improve shifting performance.

Since the “bushing” of a bushingless chain is made up of two halves that don’t connect directly with each other, this type of chain is more flexible sideways than a conventional chain. This is because the two halves of the “bushing” have a bit of “wiggle room” with respect to each other.

BTI (Sheldon Brown site), Chain Maintenance

The bushingless chain is more vulnerable to some kinds of failure. Sheldon Brown and John Allen said:

The lightweight chain of a bicycle with derailleur gears can snap (or rather, come apart at the side-plates, since it is normal for the “riveting” to fail first) because the pins inside are not cylindrical, they are barrel-shaped. Contact between the pin and the bushing is not the regular line, but a point which allows the chain’s pins to work its way through the bushing, and finally the roller, ultimately causing the chain to snap. This form of construction is necessary because the gear-changing action of this form of transmission requires the chain to both bend sideways and to twist, but this can occur with the flexibility of such a narrow chain and relatively large free lengths on a bicycle.

Chain failure is much less of a problem on hub-geared systems (e.g. Bendix 2-speed, Sturmey-Archer AW) since the parallel pins have a much bigger wearing surface in contact with the bush. The hub-gear system also allows complete enclosure, a great aid to lubrication and protection from grit.

Wikipedia on Roller chain, July 2021

Bushingless chains have tiny internal voids around the middles of pins where the half rollers on each side end. Lubricants applied to the outside of a bushingless chain flow differently than lubricants applied to bushed chains. The lateral flexibility of bushingless chains, and the effects of lateral movement on fluid on the chain appear in a video on YouTube posted in the Silca Velo channel 4See Part 4 for information on Silca Velo in April 2024 called Stop Wasting Your CHAIN LUBE! Know the BEST Way to Apply It. The wiggling action is shown in a segment about 8 minutes long, starting about 7 minutes after the beginning.

Chain Sizes

Pitch is the length of any link, outer or inner; pitch (length) is the distance between pins, measured from the centers of pins. It can be expressed as an ANSI number, or a fraction of an inch, or in millimeters. See:

The standard pitch for modern bicycle chains is ANSI 40 (designating 4/8 inch) = 1/2 inch = 12.7 mm. On the assumption that all links are counted (as opposed to counting pairs of inner and outer links) , a chain will normally be more than 100 links long. A road chain may have 108 links or more. A gravel or mountain bike chain will be longer. A chain for a compact road crankset with a 46 tooth large ring and a cassette with a 36 tooth large cog will be about 112 or 114 links long. Chain length depends on the length of the chain stays and the diameters of the largest chain rings and cogs.

The chain must be long enough to go around the largest front ring, around the derailleur pulleys, and around the largest cog on the cassette. The derailleur must be left in a position to shift the chain effectively. On measuring a chain, see:

The BTI method of sizing a chain is to break a chain (remove links with a chain breaker tool) to fit the largest rings. A chain breaker tool pushes pins (the rivets that hold the chain together) out. Another key measurement considers how the chain is tensioned when the chain is on the smallest gear wheels on cassette of drive wheel. This makes sure the chain does not fold and rub on itself.

The rear derailleur, which is found on almost all geared bicycles, imposes a total system limit, which affects the length of the chain. Adam Kerin of Zero Friction Cycling discusses the system limit in his video, on the ZFC YouTube channel March, 2023, “When 1X goes wrong“. The system limit can be calculated as the sum of the number of teeth on the front ring (or the largest front ring) and the largest cog on the drive wheel (usually the rear wheel) cassette. The system limit varies. Rear derailleurs for road (and gravel) bikes have a limit of about 84 teeth. If the front ring is 50 teeth, the largest rear cog must be under 34 teeth. “Compact” front rings on many road and gravel bikes are from 48 teeth, down to 36 teeth. The system limit for some rear derailleurs for mountain bikes is about 90 teeth – they will run a 45 tooth cog with a front ring of 45 teeth or less.

A 108 link chain is 1371.6 mm long; elongation by .5% is a fraction more than 6.8 mm. A drop-in chain checker gauge measuring about 170 to 199 mm. is used to indicate if the elongation in a span exceeds .5%. In a span of 1/8 of the length of chain, the gauge has to detect the difference in that span to a tolerance of .5 mm.

Pitch is standardized. The width of chain links varies. It is generally proportional to the number of cogs on the cassette on the drive wheel. The spaces between cogs in modern systems are so narrow that shifting is only feasible carefully adjusted rear derailleurs. Bike component makers have claimed the benefit of indexed shifters which are the components on almost all new bikes, and bikes made in the last 40 years. (Some riders still prefer friction shifters).

Cleaning the paste of lube and dirt out from between cogs requires narrow tools. Older tools for cleaning a cassette may not fit. It isn’t necessary to resort to butchers twine to floss debris out of the spaces. The changing number of cogs has made wider tools obsolete.

Bicycle chains for derailleur systems with 11 or 12 cogs on the cassette, measured by internal or external width:

  • internal – 11/128 inches = 2.2 mm;
  • external
    • 11 cog – 7/32 inches; 5.5 to 5.62 mm;
    • 12 cog – 13/64 inches = 5.3 mm.

Bike manufacturers buy chains and install the chains on new bikes. Even where the bike manufacturer uses a Shimano or other brand name drive train component set (crank arms, chain rings, derailleurs, rear cassette), the chain may be by another manufacturer. Bike manufacturers have begun to change their “current” models almost annually.

Most chains have standard dimensions. Some chains have specific features and limitations, requiring that the gears have specific dimensions and features. Component manufacturers and bike shops may suggest a chain should be made by the same brand as the rest of the drive train. This seems to be a myth.

Directions

Some chains are supposed to be installed to run in one direction. The “flat” side of a SRAM flat top chain is on the outside of the chain as it passes over the the teeth of the cogwheels of the cassette and of the chainwheel.

If a chain’s links are etched or stamped on one side, that side should be installed so that the arrow or text is visible and/or the arrow points forward as the link goes forward on the top side of the loop on the side of the bike from which the chain is accessible – the side:

  • with the cassette and the chain rings and
  • the chain passes over the chainstay moving from the driving wheel to the chainwheel.

Many chains are not etched or stamped. Some mechanics maintain that there are other ways that can determine which side of the chain should face the persons installing a chain.

Chain Gauges

The bike chain and bike tool industries developed tools to measure wear, called chain gauges (or chain checkers). Articles by the Australian cycling tech writer Dave Rome on checking for wear, based on discussions with Adam Kerin of Zero Friction Cycling (“ZFC”), and on other sources):

  • Dave Rome at Bike Radar, 2016, How to know when it’s time to replace your bicycle chain;
  • Dave Rome at CyclingTips, August 2019 How to check for chain wear: The easy way, the best way, and why (no longer on line – Outside has dropped it as of late 2023 and early 2024) The ZFC measurement methods were explained in this article). (Dave Rome left CyclingTips in 2022. He contributes to the EscapeCollective media as of 2023 and early 2024).

There are videos on chain gauges and other chain tools, and online instructions on using them. There are several inexpensive drop-in checkers by previously unknown vendors for sale online; several claim to be laser cut. Adam Kerin of ZFC has published articles and videos on checking chains. There are videos and podcasts of his interviews. Adam Kerin’s advice on chain gauges, and some of his related advice on maintaining chains, can be summarized:

  • get a simple drop-in gauge;
  • make sure it is an accurate one;
  • know how to use your chain checker and use it regularly;
  • lubricate the chain regularly and clean it frequently. The cleaning will depend on conditions and which lubricant has been used;
  • consider checking chains on long rides and the possibility of replacement along the route;

For his ZFC chain wear (elongation) tests, discussed in Part 4, Adam Kerin used the (expensive) KMC digital caliper chain checker. Adam Kerin says a drop-in metal gauge is a sufficient tool for the rider/home mechanic, but”

  • cautions that drop-in gauges must be precisely made in video episode 5 of the ZFC YouTube series;
  • recommended the Shimano TL-CN42 because it is cut to the exact tolerance, and reliably free of manufacturing errors. The tool was not on Shimano’s US sites in early 2022 (or in 2023). Some dealers advertised at that time. It was out of stock at ZFC as of February, March and April 2022 but in stock at ZFC in late 2023 and early 2024. It was selling for nearly $90 (Canadian) on Amazon at times 2023-24.
  • said that many drop-in gauges are cast and finished poorly, and do not measure the short span to the tolerance required.

In his YouTube Video of February 2, 2024 on his ZFC channel, he discussed the drop in gauges which were known to accurate enough, without any reports of varying measurements between individual products of the same model.

He published his findings in a chain wear checker table. He said a few of the drop in gauges were accurate:

  • Shimano TL-CN42
  • Park Tools CC-4
  • Pedro’s
  • Abbey Bike Tools LL Chain Wear Tool 5Abbey Tools in advertising this tool in 2024 says “Most chain wear tools currently on the market are laser cut metal. This is a pretty cool process that’s great for making sheet metal parts, problem is the accuracy of this process isn’t great at +/-.010″ (.254mm). If you add the error of the tool itself to the roller variable it’s possible to double the error of the tool”.

Adam Kerin did not recommend the KMC digital caliper chain checker, on the basis that it is not a drop-in gauge, and is not inexpensive.

Dave Rome, the CyclingTips tech editor and correspondent in Australia described the subject of measuring chain wear as “murky” on the Ask the Mechanic segment in the NerdAlert podcast episode recorded February 21, 2022 6no longer on line – owner of the Outside family of content unpublished it as of late 2023. He noted the Park Tool CC-2 gauge is capable of some precision but is vulnerable to bending of the pins affecting the accuracy of measurement. He thought the Park Tool CC-3.2 drop-in gauge was reliable for most chains except some SRAM 12 speed chains. But Adam Kerin had reservations about it.

I had a ParkTool CC-3.2. It sold for about $12 US from US online bicycle supply stores (and for $18 or $35 from vendors in the Amazon market jungle) in 2022. I had no context or background on how often to use this or any chain checker. In 2022, I was wondering if it was accurate. I had a new chain available. My kludge to confirm my gauge was good enough: I tried it on a new chain (making sure the chain was taut). The tip did not drop in, and the tip did not pass the midline of the pin inside the roller the tip was touching.

The CC-3.2 measures total elongation – it does not “isolate” the rollers. It has hooks at one end, on each side, to fit against a roller. One side is machined to detect .75% wear. One side is machined to detect .50% wear in chains for 11 and 12 speed cassettes.

SideChainDistance
Hook to Tip
.75%7-8-9-10 speed≪172 mm
.50%11-12 speed≅171 mm

The manufacturer’s instructions recommend dropping a hook end into an inside link. The user should ensure the chain is taut and the hook is held against the roller. Park Tool says the device can be used at the top or the bottom of the loop (between chain ring and rear cog) – the derailleur spring should be pushing the chain taut at the bottom. This gauge spans nearly 14 pins; the tip can touch or fall short of the 14th roller. A chain is elongated when the tip falls does not rest on the roller at the other end (it is falling short) and drops into the inside of the link. The Park Tool CC-3.2 chain gauge measures a span just over 170 mm. to indicate if the elongation in a span exceeds .50%. In a span of 1/8 of the length of the chain the gauge has to detect the difference to a tolerance of .5 mm.

I started to use a Park Tool CC-4 and the Abbey Tools device in 2024.

Wear

How/Why

Open bearings are vulnerable to contamination. Roller chains have to be cleaned and re-lubricated. Even well maintained roller bearings will wear. A metal roller chain wears. This makes chain get longer. The plates and pins do not stretch, compress or deform.

The cause of elongation is believed by some riders to be “stretching” of the chain. Josh Poertner of Silca Velo 7noted in Part 4 of this series discusses wear as the cause of elongation, using a digital microscope device, to produce the video Microscopic Magic: Save Your Chain from Wearing Out! (July 30, 2024) to look at a badly worn chain (a SRAM PC 1051)

Some count 1 link as a set of 1 inner half-link and 1 outer half-link; others count all links.

Microscopic wear on individual links adds up. One of the consequences of wear is elongation. An elongated chain fails to fit the gears (cog wheels) – the chain wheel and the toothed wheel on the cassette on the rear wheel, cause wear on the gears.

With modern 11 and 12 speed bushingless chains, elongation of .5% (half of one percent) of the length of the chain leads to replacement. A chain may show almost no elongation wear for several hundred Km., and then wear rapidly. Chain wear is not linear.

Consumables

Bike, component and chain manufacturers expect consumers to accept chains which have limited durability. Purchasers of new bikes may have to replace or upgrade the chain frequently. The bike, component and chain manufacturing industries expect bike chains have have a short service life, which is defined as a short mean time before failure. Failure can mean breaking but it usually means elongation by wear.

They sell bikes with chains they expect to fail within a few thousand Km. of use.Whether bike and component manufacturers follow a strategy of planned obsolescence might be debated. The inspection and replacement methods used for industrial machines and motor vehicles – e.g. days or hours of operation or distance – do not work for most bikes and chains.

Few modern chains are good for more than a few thousand Km before becoming measurably worn – durability varies with chain material, riding conditions, lubrication and cleaning practices. Bike manufacturers trust the chain manufacturers. Consumers trust the manufacturers and the market.

Importance & Origins

Master links, devices that replace a single outer link, were noted in the BTI (Sheldon Brown) glossary. Master links for chains for single speed drive train chains were once rare. A few custom metal fabricators made and sold universal master links for derailleur shifting chains by any manufacturer on the market by the 1990’s – e.g. the Craig Super Link. Before master links, removing a chain involved pushing a pin out with a chain breaker tool, Installing a chain involve peening8some chainbreaker tools have peening anvils, and are capable a pin with a tool.

The master link makes removing a chain for cleaning, maintenance and replacement easier. Chain manufacturers developed proprietary master links for some of their chains. One of Shimano’s systems secured the master link with a special pin. Some manufacturers had three part links – 2 link plates and a spring plate to slide over the pins and clip the links. Connex/Wipperman still sells this kind of link. A few other universal links came on the market. The manufacturers were small or fabricated the devices in limited quantities. Some non-proprietary or univeral links are on market or in use. Some master links can be used by any chain of a given size, by any manufacturer. Master links can be used on chains are built to the standards of the pitch and width for compatibility with the number of cogs on the cassette on the drive wheel (i.e. links are machine to work on “11 speed” chains exclusively). Some manufacturers market links as compatible with other manufacturers’ chains of the same size – e.g. YBN. Others insist on branded links for their branded chains.

Many master links involve two parts. Each part is one link plate with one solid pin riveted to the plate. The pins are machined with a groove or slot at the free end that fits into a machined slot and hole in the opposite plate. Connex Wipperman uses curved slots for some models, and straight slots for others. Many manufacturers have one straight slot model in each size. For instance see the YBN product. Two part systems depend on getting both pins into the opposite slots and locking the link. Two part master links are made by Shimano, SRAM, YBN, KMC and others. The manufacturers’ names for their master links may cause some confusion.

Most two part master links are sold as “single use”. YBN’s 2 part master links, labelled Safe Sections and QRS (Quick Release-Safety) are sold by YBN and by vendors who (re)sell them as safe for five uses.

Josh Poertner, of Silca Velo shows how two part master links work in the June 26, 2024 Silca Velo video Chain QUICK LINKS: Are they keeping you from waxing?

Removal and Locking

Riders commonly reuse master links. Some users only remove a master link to replace a chain.

A master link may fail. The finely machined slots are vulnerable to microscopic, nearly invisible wear, fatigue and stress. The risk of the failure is real.Often failure is caused by improper installation. It is sometimes caused by wear of the finely machined slots in the pins and plates – which can be caused by removing and locking the link too often or damaging the locking slots.

Needle nosed pliers are too wide to close or open a master link on modern narrow chains. There are special pliers that can open and/or lock a link. Locking the master link without a locking tool depends getting the pins into the slots, holding the bike steady and stepping on a pedal.

A master link can be removed with master link pliers, like the Park Tool MLP-1.2, which is sold in bike shops and online for about $17 to $25 US. The Park Tool pliers can be used to lock or remove a master link, and can fit a chain as narrow as a 12 speed chain. There are other master link pliers on the market. Most are bulky or heavy enough that they will not fit in a seat pack. Light compact travel tools are available. Some of the compact tools store replacement links. The parts of a master link can be easily lost.

Master links are durable but vulnerable to wear and stress in places – the slots that hold and lock the pins. Immersive waxing requires removing the chain at intervals of a few hundred Km.

A user trying to remove a link from a chain on a bike will need to address the tension in the chain caused by the rear derailleur spring. When the link is released and pins are clear of the slots, the chain can snap, flinging the parts into space. Putting the chain on the smallest rear cog and the smallest chain ring (in 2x or 3x systems) reduces the tension. The user has to keep a grip on the chain which may be dirty and greasy. Some chain breaker tools have a wire accessory – the thickness of spoke – bent just less than 90 degrees at each end. This can be detached from the tool body and slipped over rollers of links beyond the master link. Some users make such an item with a piece of scrap spoke (a coat hanger may fit into outer plate links but not inner plate links in 10 speed or narrower chains). Some will shift to the smallest chain wheel and the smallest cogwheel on the cassette and manual take the chain off the chainwheel to remove the tension.

3 thoughts on “Bike Chains, Part 2”

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