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My (trekking) bike has 9 gears (9 sprocket wheels at the rear wheel / Shimano Acera). I just wanted to replace sprocket and chain. I correctly bought a 9-speed chain but the length is wrong. My old chain has 118 links and the newly bought chain 114 links.

There are two reasons why I'm wondering whether I can still use the 114 link chain on my bike:

  1. because I have it already
  2. because 118 link 9-speed chains seem to be in short supply

So, what happens if I just put the 114-link chain on the bike? I assume this will make it necessary to readjust the gearing. Or is this not possible at all?

What are my options?


Bonus question: is there a qualitative difference between 114 and 118 links? Or is it just a different length and that's it?

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    Usually bike chains are sold with extra length, so the user can cut them to the required length. It would be very unusual for a new from-the-factory chain to be shorter than the one installed on your bike. – Daniel R Hicks Apr 19 at 17:40
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    @DanielRHicks it’s very common with some bikes, in my experience. Cruiser-type bikes like the Electra Townie, with theor long chain stays, are a common one for us. I also find the chains we’ve been getting for some time are a link too short for some comfort/hybrid bikes. When that comes up, we just splice a few links in from an extra chain, and keep the remainder of the second chain for the next time. – Pisco Apr 19 at 18:08
  • @DanielRHicks: but that's how it is. I bought the bike new and it came with that 118-link chain. It's a "regular" Trekkingbike (raleigh-bikes.de/de/bike/bike-modelle-2019/rushhour-20-disc) – Raffael Apr 19 at 18:29
  • The number of gears in the back is totally irrelevant. The chain must be long enough so that you can shift onto the largest ring in the front, and the largest sprocket in the back. Then, another concern is: if you shift on the smallest ring and smallest cog, that the derailleur doesn't "crash" so that the chain is rubbing against itself. In that situation, either the chain has too many links, or else the derailleur's cage is not long enough to pick up the maximum difference in the gearing. – Kaz Apr 20 at 16:00
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    @Raffael It is totally relevant, just not to the issue of length. – Kaz Apr 21 at 6:02
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Chainstay length, size of cogs, and drivetrain type, are the factors that dictate chain length.

The type of drivetrain affects chain length because different group sets have different methods for measuring the correct length. It’s not necessarily as simple as putting the chain over the largest cogs and adding two links, anymore. If you were installing a whole new drivetrain, (or just chainring the size of either the cassette or chainrings) it would be best to look up the service instructions for how to properly measure chains on your system.

Chainstay length is self explanatory- a bike with a longer distance between the rear axle and the bottom bracket will need a longer chain, all else being equal. On full suspension bikes, the chainstay is often longest in position of full travel, so that’s usually required to determine the appropriate chain length.

Cog size also determines chain length. As you can tell from the traditional method, an improperly sized chain will have problems when you try to use certain gear combinations. On many modern drivetrains, the rear derailleur guide pulley is not concentric with the RD cage pivot, so chain length also affects the derailleur’s ability to track the curvature of the cassette. A major problem with running too short of a chain, is that shifting to larger cogs can damage the system. In theory, you can avoid damage by determining which rear cogs (if 1x) or which sprocket combinations are safe before riding (turning the cranks in a work stand, and watching the derailleur cage while carefully shifting from smaller cogs to larger ones) but that damage can happen quickly when you’re not thinking about it. I wouldn’t recommend riding like that unless you can eliminate that risk by locking out the larger cogs with the derailleur limit screws.

My recommendation for you is to get the links necessary to run your chain at the correct length. It’s not uncommon in bike shops to need more than one packaged chain for a bike, because tandems, and recumbents, and many hybrids and beach cruisers, require longer chains than what comes in a single box. When we open two chains for one bike, we hold on to the remainder of the second one, so we don’t waste two complete chains on every such bike- we just cut the extra links from the extra 9 (or 8, etc) speed chain in the drawer, and connect them using a connecting pin or quick link as appropriate. If I were in your position, I would ask around at your local bike shops for a few links from a spare 9 speed chain, or, consider buying a second chain, taking the needed links from it, and keeping it around for the next time you need a few extra links of 9 speed chain.

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As others have indicated, the short answer is "it depends." If your 118 link chain was a bit long, it'll be fine. If your 118 link chain was the correct length, the 114 link chain won't work.

You can find a great guide to figuring out the correct chain length on Sheldon Brown's website. You'll have to scroll down the the "Chain Length" section.

Essentially, you run the chain around the larger gears in the front and back without running it through the derailleur. You want the chain to be long enough to overlap by a full link. I've added an image below from Sheldon's site.

correct chain length

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    The term "link" is a bit ambiguous. In common parlance, you're correct. However, bike chains are funky in that there are two different types of "links" and that two sections of chain have to terminate in opposite types of link in order to be connected together. To put it a different way, it's impossible to make a bicycle chain with an odd number of links. For this reason, Sheldon and others, including myself, tend to refer to a single piece of chain as a "half link." Two half links make a full link. The picture shows one full link overlapping. – jimchristie Apr 19 at 19:06
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    Chains are not sold like that though and you are using terminology that is incorrect in the real world and only serves to confuse newcomers further. The 114 link chain goes around your drivetrain twice, i assume. – JoeK Apr 19 at 20:44
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    The terminology that I'm using isn't "incorrect in the real world." It's relatively common in the cycling community. Indeed you can find multiple instances of people using it on this site. And both ways can cause confusion. – jimchristie Apr 19 at 23:17
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    @JoeK yeah words can be confusing. "Half link" and "Full link" (ie two half links, one wide and one narrow) are unambiguous phrases, but "link" by itself might mean either. – Criggie Apr 20 at 0:11
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    Nobody anywhere sells chain links described any other way (bushings aside). What people say on forums isn't so relevant. A half link, for anyone who is interested, combines half an inner and half an outer link into one link. It has probably helpfully contributed to this misunderstanding. – JoeK Apr 20 at 6:36
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Sometimes the length as provided (114, 116, 118) happens to be the exact length needed, but the norm is to size it down by removing some number of links.

The optimal length is determined by the size of your big back gear, your big chainring, and your chainstay length, with some length added on top of the minimum those factors will allow depending on the derailleur in question. If you go too short you can break your rear derailleur, derailleur hanger, chain, and/or or frame by shifting into a gear combination that overextends the rear derailleur.

Nine-speed trekking bikes can be outliers for chain length. The usual scenario for this is a 48t large chainring, 34t or 36t cog, and long chainstays, i.e. 450mm+. That bike setup being a mainstream entry in some regions is basically the biggest reason 118 link chains even exist. It's very possible you can't get away with 114.

Kindly request to buy a cut-off segment of new 9-speed chain from a bike shop plus two two-piece master links to splice it in, or Shimano pins if it's a Shimano chain and segment and if you're confident with that. (More finicky). It's not pretty but will be fine. In practice the SRAM and KMC two-piece links work with whatever 9-speed chain (except Campy) without issue, don't worry about that part.

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My (trekking) bike has 9 gears (9 sprocket wheels at the rear wheel / Shimano Acera). I just wanted to replace sprocket and chain. I correctly bought a 9-speed chain but the length is wrong. My old chain has 118 links and the newly bought chain 114 links

Most likely the new chain is way too short.

A trekking bike sounds like a bike that:

  • Has a triple crankset with 48-tooth big ring as opposed to tiny "big" rings typical of MTBs
  • Has decent length chainstays as opposed to road bikes that often have ridiculously short chainstays
  • Has a rear cassette where the big sprocket is perhaps 32, perhaps 34 teeth.

For example, I have a touring bike with 48-tooth big ring, 11-30 cassette and 47 cm chainstays. The chain length calculator tells that it requires 116-link chain. I could have put a 11-32 cassette or 50-tooth big ring there but either choice would necessitate a 118-link chain and finding such a 8-speed chain with low shipping costs from an online store that has something else I may want to order at the same time is hard, especially if I limit myself to only Shimano chains as those have the superior reinforced pin based connecting system. Of course there are 138-link chains but such chains are so expensive I am unwilling to pay the price. In contrast, 116-link 8-speed chains can be easily bought from many different online stores. So that's why I limit my big ring and big sprocket sizes.

Unfortunately, we live in a world where those with the money buy predominantly bikes from either the "MTB" category (where the biggest chainring is so small that it's wonder why the bikes make any forward progress at all) and "road" category (where the chainstay is so short that anything larger than 23 mm tire will jam as it touches the seat tube). Those with the money won't purchase bikes from the "reasonable" category. So we are in a world where it's all too easy to buy a chain that is too short, but very hard to buy a chain that's the right size for a decent bike.

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    Do you live in the 1990s? 23 mm road tyres have been completely démodé for a long time. People who have the money copy what the pros do and they have been using 25 mm for a long time and 28 mm on selected very-popular cobbled races (Paris-Roubaix). – Vladimir F Apr 20 at 18:18

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