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How does chain wear occur?
Every three turns of the crank, the chain has travelled once completely in a circle - a very average calculation. If you think about how many laps that is in a year, you can better estimate the stresses and strains involved, but also the significance. Would you like an example calculation? With a performance of 3000 kilometres per year, which is a very conservative estimate for commuters, for example, and a deployment (distance covered with one turn of the crank) of around four metres, we arrive at a quarter of a million chain laps.
An impressive figure, even at the optimum Lubrication and CleaningWith the daily sand, dirt, rain and salt in winter, even good quality chains and sprockets (cog or cogwheels on the rear wheel hub) and chainrings (cog or cogwheels on the crank) reach their limits. The manufacturer's specifications regarding these parts and their durability not only vary greatly in terms of the different quality levels, but the width of the chain also makes a big difference. This is why there are differences between single-speed drivetrains (for bikes with one gear or those with a gear hub or gearbox) and those with several sprockets on the rear wheel.
5 tips for detecting chain wear
There are several ways to determine whether you should replace the wearing parts of the drive - especially the chain. Some are more practicable, some less:
- If the shifting function is unreliable despite a well-adjusted chain line, this may be due to chain wear.
- When links rust and become stiff, i.e. can no longer be easily moved against each other by hand.
- A wear gauge (see above) is the most effective method. Abrasion of the chain surfaces and minimal deformation between the link plates and pins causes each link to stretch a little. A gauge like the CC-4 from Park Tool records the "elongation" of seven links and shows the state of wear in four stages: 0% / 0.5% / 0.75% / 1%.
- According to the manufacturer: There is a clear recommendation for each chain model that you can follow. In general, however, these kilometre intervals are quite short, more like a best-before date.
- Pull test (only for derailleur gears): put the smallest sprocket on the rear, the largest chainring on the front and try to pull the chain away towards the front wheel at the front end in the direction of travel. If there is a gap larger than a match head, the chain should come off.
Not recommended: There are also millimetre measurements circulating on the internet that are supposed to be between the rivets of a total of ten links on fresh and used chains. Theoretically, this is just as precise as the measuring gauge, but it is practically impossible to hit the exact centre of the rivet.
Safer and cheaper: Timely chain maintenance
You might think that you could wait to replace the chain until the function really suffers noticeably due to chain wear. But anyone who has ever broken their chain while pedalling will really appreciate a reliable drive. In most cases, this worst-case scenario is accompanied by an accident, not to mention the total failure of the drive. However, timely maintenance has another major advantage: with a "stretched" chain, the spacing of the links no longer matches that of the sprockets. As a result, the metal parts rub or rather grind hard against each other during rotation. The wear on the sprockets increases exponentially.
The calculation is simple: It's better to replace a chain for 20 or 30 euros than the sprockets for three or four times as much. If that's not enough of a reason, a poorly running drivetrain with a dirty or worn chain costs around 20 watts of pedalling power, which for the average cyclist is 15 to 20 percent of their power! Speaking of maintenance: Regular cleaning and lubrication of the chain extends its service life many times over. Long downtimes in the rain, on the other hand, accelerate chain wear. Meticulously maintained, chains at Shimano XT level can last 15,000 kilometres instead of the recommended 2,000!
Chains on single-speed drivetrains last longer
Singlespeed chains are wider and quite robust even without this level of care. A certain amount of abrasion on the metal of the links has no negative effect on shifting comfort or tensile stability. Such chains also only slip over the cogwheel under high pedalling force if their tension is insufficient. The wide models only need to be replaced when the chain is one per cent worn or when they have become stiff due to dirt and weather.
TIP: invest in stainless material!
Especially because single-speed chains stay on the bike for longer and to maintain the ease of maintenance of the drivetrain, a rust-free model for 30 to 40 euros is worthwhile here! In the case of derailleur gears with eight, nine or ten sprockets, the chain "may" wear by up to 0.75 per cent, i.e. become longer, according to our recommendation and that of workshop expert Park Tool. Modern derailleurs with eleven or twelve sprockets on the rear wheel work with so little tolerance that they should be replaced at half a per cent, and the equally narrow sprockets would be even more expensive if you wait too long.
Shimano and Sram products are officially compatible with each other, but experience shows that the latter's own chains work best. And don't be afraid of "third-party products", KMC or Connex, for example, deliver excellent quality, they just have to be labelled Shimano/Sram-compatible. Specialist shops will ask you exactly that when you buy a chain - and how many sprockets the bike has.
How the bike chain replacement works
A bike usually comes from the factory with an endless chain, so there is no place intended for opening. To do this, you have to press one of the pins out of the chain with the chain rivet as if using a screw clamp. Caution: If the new chain does not come with a lock or a new pin, do not push the rivet out completely!
After removing the old chain, it is also a very good time to thoroughly clean all sprockets with a Brush and ideally a Chain cleaner, including those of the rear derailleur. If it is clear that the chain is to be disposed of, you can of course open it with a bolt cutter. Use the old chain as a blueprint for the length of the new one before throwing it away. New chains are almost always a little too long. The excess links must be removed - also by pressing out the rivet pin - and at this point at the latest you will need the appropriate tool.
The right tool
Please note: If a chain lock is to be used, two inner links must remain, i.e. the narrower parts of the chain. If a rivet or bolt is to be used to lock the chain, one pair of inner links and one pair of outer links must be left. Before you finally close the chains, you should test the length. You can easily make a super-practical tool for this yourself from slightly stronger wire, the ends of which you bend over and thus provisionally close the chain, of course without the bend, which is practical when opening and closing power links, quick links or master links, as the locking pieces are called.
To test the correct length of the chain, it must run over the smallest sprockets of the drive, i.e. on the rear wheel all the way to the right and on the bottom bracket - if there is more than one - on the left chainring. The chain tensioner of the rear derailleur should now be approximately horizontal and the chain should not sag, but should already be under tension. If it is sagging, two or four more links need to be removed. If the rear derailleur is already clearly pointing downwards, it is better to try again with two more links.
Chain fastener
There are many ways or products to close a chain again. This makes it somewhat confusing. The selection of fasteners in the following image shows a new chain rivet with an insertion aid on the right, which can be used after pressing in with a chain rivet pusher (e.g. Parktool tool CT-3.3) or a comparable tool is simply broken off using pliers. To the left you can see a chain lock where one of the outer plates is removable. The two pins on the fixed link plate are pushed through the ends of the new chain, the single link plate is fitted and the silver safety slide is pushed over the pin ends from the front until it clicks into place.
At the top right of the picture you can see one of two identical, matching outer plates, each with a fixed chain rivet. They are inserted into the chain mirror-inverted, which should be slackened using a retaining wire. The pins fit exactly into the widened recess of the counterpart, pulling on the chain causes the pins to pull into the narrower part of the eyelets and snap into place, as can be seen in the example of the picture with the chain lock. This is one of the most common variants. To open, the ends of the locking link - for example with the Parktool pliers MLP-1.2 - towards each other until the bolts are released from the catch and can be removed at the wider point of the opening.
Finally, the simplest locking piece at the top left: Here, too, there is an outer plate with two fixed pins and one without chain pins. The rear section is inserted into the chain ends, the "free" outer plate only fits onto or over the pin ends if the chain is bent towards the open side. If both holes sit on the notches in the pin ends and the chain is released again, this is actually enough to ensure a tight fit. Incidentally, most chains come with a locking piece, but you can also buy them separately for an average of one euro.
Chain wear: What happens after replacing the chain?
Riders of most hub gears and gearboxes must remember to restore their tension after fitting the chain. To do this, the rear wheel generally has to be fixed a little further back in the dropout. Chains come from the factory already lubricated. If the sprockets have not been replaced, the running noise of the chain may be a little rough for the first few kilometres, but this will disappear. Some cyclists keep the removed, surplus links in order to have a visual reference to the condition of their chain.
Replacing the bike chain: You need these tools
The Wear gauge CC-4 (below) is inserted into the chain from above with the two right-hand pins, the right-hand pin of the two ensures correct seating. With new chains, the pin on the far left then rests on a chain pin. The further the seven links between the measuring pins are worn out, the deeper it sinks into the chain in four stages. The Chain rivet pusher CT-3.3 (left) opens and closes chains without a separate locking link by the retractable mandrel pushing the rivet out of its socket; however, the inner and outer plates of the chain are supported by the tool.
The MLP-1.2 pliers for opening existing chain locks (right) is not a must, but many hobby mechanics have already pinched their fingers with conventional pointed pliers or combination pliers. The slightly claw-like tips fit exactly around the two chain pins of such a locking link. By closing the pliers, they are pressed towards each other, which safely and reliably unlocks the fastener.
