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Chain reactions - a closer look at bicycle chains

Andy Waterman
31 May 2016

It lacks the glamour of a carbon wheel or an electronic derailleur, but the humble steel chain is vital to the smooth running of your bike.

Tao Geoghegan Hart was having a dream season in 2013 and if there was ever a dead cert for the junior rainbow jersey, the 18-year-old Brit was it. But cycling rarely works like that. Geoghegan Hart recalls, ‘The race was going perfectly to plan. I had all of the sensations of top form, but then, with three-quarters of a lap to go, I noticed the chain jumping a little. Suddenly my legs were spinning round uncontrollably. I looked down to see nothing there – the chain was gone.’ And with it, any chance of winning. 

Geoghegan Hart wasn’t the first rider in history to have their shot at glory thwarted by a broken chain (who can forget David Millar’s bike-throwing antics when his chain snapped while sprinting for victory in stage five of the 2008 Giro?) and nor will he be the last. We put a lot of trust in those hundred-odd links of steel, rarely questioning their role until something goes wrong. The fact that these days, something goes wrong so rarely – even as chains have gone from thin to thinner to positively waif-like – is testimony to the engineering, design and materials used in this under-appreciated component. Without a chain a bicycle is little more than an expensive hobby horse, barely faster or more efficient than walking. Maybe it’s time we gave chains the consideration and appreciation they deserve… 

‘At a glance, bike chains appear to be the same as they have been for years, but the reality is that a chain from 30 years ago and one from today are about as similar as a deep section carbon wheel and an old aluminium-rimmed, 32-spoke wheel,’ says Joshua Riddle from Campagnolo. While the job of a chain remains the same as it’s always been – it needs to engage perfectly with the teeth of the chainring and cassette, rolling smoothly without wearing too quickly – the addition of more sprockets in modern drivetrains, and striving for perfection in every gear, has only complicated matters. 

‘With more gears – first the jump from seven to eight, then nine to ten, and now 11-speed cassettes – the space available for those gears is continually decreasing,’ Riddle adds. ‘Cramming in more sprockets means less space for the chain so they need to be slimmer and all components of the drivetrain made more precisely. The chain also needs to accept a higher degree of torsion as it needs to cross over 11 sprockets.’

People overlook the fact that it’s as much a safety component as a performance component.

As the youngest member of the big three groupset manufacturers, SRAM got a head start on its component development by buying the German chain manufacturer Sedis-Sachs, the company that first pioneered a bushless chain in the 80s. This technology – at the time revolutionary – allowed the chain to have more lateral flexibility thanks to a lack of bushings, and thus paved the way for the increasing number of gears we see today. 

‘Before acquiring Sachs bicycle division, SRAM didn’t have the level of expertise and knowhow regarding key materials, technologies and production processes, such as steel stamping and heat treatment,’ says Frank Schmidt, SRAM’s lead drivetrain engineer. ‘It would have been very unlikely that SRAM would have started from scratch. It’s very difficult and costly to start with nothing, especially for this type of product that requires years of expertise. That’s probably the reason why we don’t see any new chain companies emerging.’

Linked in

Bicycle chains start life as sheet steel, which is then fed through a powerful punch press to stamp out inner and outer plates, at a rate of around 10,000 links per hour. 

‘The difference between chains at different spec levels are materials, finishes and features such as hollow pins and cut-out plates for lighter weight,’ says Schmidt. Those more complex chains with cut-outs require a more intricate stamp to remove more material while retaining precisely positioned chamfers that assist with gear shifts. Samples of each link are sent to quality control to ensure the position of each link is correct and the hole is precisely the right size. After heat treatment to harden the steel, the links are polished and prepped for further treatments, normally PTFE or Nickel Teflon coating to resist corrosion, and to ensure the links roll smoothly on and off the teeth of the chainrings and sprockets. More expensive chains usually get pricier coatings, with Shimano’s Sil-Tec, KMC’s Diamond Like Coating and Campagnolo’s Antifriction Ni-PTFE at the top end of the scale. The inner and outer plates don’t necessarily get the same treatment because each has a different role. The outer plates only come into play when shifting from inner to outer chainring, while the inner plates connect with cassette sprockets as the chain climbs.

With coatings applied, the chain is assembled by a machine, which places spacers in between the links and presses a connecting pin through to keep the chain together. The chain then passes through a magnified inspection station to be analysed for flaws, before being dunked in a bath of hot oil to lubricate the links. It then passes over absorbent material to remove excess oil before being cut to length – typically 114 links.

To create very slim chains without compromising strength – chains that can mesh silently across a multi-geared platform while also being able to resist fatigue within acceptable limits – is a feat few companies have mastered. To keep up with ever-evolving gear ratios on bicycles, chain manufacturers have had to work with new materials and develop techniques to individually sculpt links that can perform better under load and across the whole range of gears. 

Riddle reminds us, ‘A chain from the past was relatively two-dimensional. Modern chains have a meticulously studied three-dimensional design developed in tandem with the rest of the drivetrain components for the two to function seamlessly together. There are [differing] profiles placed onto each link that help to move the chain up and down over the chainring and cassette teeth.’ But he’s also at pains to point out that despite the increased need for performance, reliability is still the most important factor: ‘People overlook the fact that it’s as much a safety component as a performance component.’ 

He has a point. Imagine the result of a failing chain as you powered along out of the saddle in a bunch sprint. While efficiency and weight are undoubtedly on the list of criteria for modern chains, at the forefront of any designer’s mind is reliability.

You are the weakest link

The weak point in any chain tends to be where it’s joined together after installation. To make that process as problem-free as possible, manufacturers have come up with a variety of methods to join chains, ranging from brand-specific tools to quick links and, in Shimano’s case, a special long pin that you snap off once the link is set in place. Interestingly, of the big three groupset manufacturers, SRAM is the only one currently employing a quick link, tool-less joining method. 

‘PowerLinks and PowerLocks were designed to be safer, easier and tool-free, not only for the end-users but also for shops and bike brands,’ says Schmidt. ‘The feedback we receive, especially from shop mechanics, is that they really like the simplicity of this feature when it comes to assembly.’ 

As production director at Condor Cycles, Neil Manning sees a lot of bikes, destined both for customers and the Rapha Condor JLT race team, so he sees a lot of chains too. As an industry veteran, he advocates using a cheaper chain but replacing them more regularly to maximise the lifespan of your entire drivetrain. 

‘Our race team uses [Campagnolo] Record components, but they’re changing the wheels so regularly we give them Chorus chains and cassettes,’ Manning says. ‘The bikes are already at the UCI [weight] limit so they don’t need the savings offered by Record, and the team might get through 50 cassettes per year, but as many
as 250 chains, because they change them often – maybe 20 chains per rider per season.’ 

How to oil a chain

It’s a message echoed by all the teams and mechanics we spoke to: check your chain regularly and replace it as soon as there are any significant signs of wear. All were also equally quick to remind us that the major factor when it comes to making chains last as long as possible is to keep them clean. 

Read more - How to clean a bicycle chain

‘A dirty chain wears everything away quicker,’ says Sam Hayes, service course manager for the Madison Genesis team, referring to the whole drivetrain. ‘A gritty chain will wear away chainrings and cassettes at an incredible rate. To clean the bikes after a race, I use a quality degreaser applied with a hard brush – bike in the stand, rear wheel still in – and I coat the whole thing. I do that before getting it wet, no matter how dirty it is. If you look after a chain it will last miles – and then there’s no need to replace them as often.’

There are a few simple things you can do to extend the life of your chain. Regular readers may recall our science feature on gearing, where we looked at the effect of riding cross-chained – big chainring to big cassette sprocket. Leading engineers were clear in their opinions that this was potentially damaging for chains. Hayes agrees: ‘Staying in the big ring at all times might make you feel like a Pro Tour hero, but it’s costing you money. Riding cross-chained really kills the chain, plus it’s not efficient as there’s more resistance.’ The advice, it seems, is if you’re an amateur and you pay for your own parts, drop it down to the small ring earlier.

The remaining issue is how best to lube a chain? The advice from leading mechanics once again seems unanimous – wet, sticky lubes pick up a lot more grit, so choose lubes that don’t get so filthy. Also a ‘less is more’ strategy is preferable, where frequent, small applications of lighter lube between regular cleans is a better bet than one big dose of a heavy oil. 

Read more - How to oil bicycle chain

Future links

If you visit bicycle trade shows and look in the corners away from the mainstream road cycling brands, you will see a smattering of other methods of propulsion on modern bikes, most notably belt drives. But despite the efforts of technology to improve on the humble steel chain, it looks like it is here to stay for at least
a while longer.

‘The current chains we have in the market are still superior in terms of efficiency compared to any other power transmissions,’ says SRAM’s Schmidt, who concludes, ‘It will take several years, maybe decades, before a belt drive can perform as well as a chain.’ It’s a sentiment echoed by Shimano’s Rudy Bouwmeester, who says, ‘Developments can always be made, but the chain is still the most efficient form of transmission for the bicycle. There are other reasons for developing alternative transmissions, for example lowering maintenance or for appearance, but we don’t expect any changes any time soon.’ 

Campagnolo feels slightly differently to the other two groupset giants, with Riddle saying, ‘It would be easy to look at current technology and infer that it could get no better, but that is certainly not the case. Materials are in constant evolution, production techniques are improving, and engineers are looking constantly at ways to improve each and every part. As such, I wouldn’t rule out an eventual improvement on what is already an exceptional, if often overlooked, part of the drivetrain.’

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