A loose bike chain won’t keep you from riding, but it can prevent you from experiencing a fulfilling ride. It can lead to lousy shifting, chain dropping, chain skipping, and accelerated drivetrain wear. Fortunately, if you want to know how to tighten a bike chain that’s come loose, the answer’s right here. What’s more, there’s nothing to it!
How To Find Out if Your Bike Chain Is Loose
A loose bike chain means the chain is too long for the bike. So, take a look at the chain from the sides, leveling your eyes with it. It doesn’t fit right if the chain sags below or close to the chainstays as it hangs between the chainring and cogs. It could skip as you pedal or even fall off the gears. Additionally, it may result in poor shifting in derailleur-outfitted drivetrains.
On drivetrains without derailleurs, it should be possible to lift the chain half an inch above its resting position at the chain’s middle right above the gears. A too-tight chain might make you feel or hear binding in the drivetrain upon pedaling, but a loose one might drop or skip and should sag pretty obviously.
You’ll know that bikes with derailleurs have a loose chain when the chain sags upon setting the gear combination to “small-small.” Should the chain be too tight, the rider would find it difficult to shift into the “big-big” gear combo. It is worth noting that shifting into these gear combos is for testing purposes, as they are not practical for actual bike riding.
Riders should not have trouble shifting into either of these gear combinations using the right-size chain. You’ll feel neither a sagging nor a tightness in the chain that negatively impacts your bike riding.
What Happens When the Bike Chain Is Loose?
A loose chain accelerates drivetrain wear, which can lead to premature replacement of the cog, freewheel, cassette, chainring, or chain.
Moreover, the chain may fall off the gears unexpectedly, leading to loss of balance for the rider as he pedals and potentially resulting in a crash. The chain might also get stuck in other sections of the bike and cause damage. For instance, the chain may wedge itself between the frame and crankset, large cog and wheel spokes, or frame and small cog potentially damaging these parts considerably.
Gather the following tools and adjust the chain tension:
- Hex wrenches
- Chain tool
- Master link pliers
- 15mm wrench
Sizing and Adjusting Chain Tension on Bikes With Derailleurs
Bikes with derailleurs should have a chain with enough links that it does not sag when in the “small-small” gear combo and is possible to shift into a “big-big” gear combo.
That said, the chain may sag in “small-small” for a bike with rear suspension since the chain tends to require a couple of extra links to ensure the lengthening of the rear triangle when the suspension compresses. Thus, check the manual for accurate information on chain sizing.
In general, these are the steps for sizing a chain correctly:
- Wrap the chain around the rear’s largest cog and the front’s largest chainring, bypassing both derailleurs while doing so.
- While holding one end of the chain against the largest chainring’s teeth, grab the opposite end and fold it around the freewheel or cassette’s largest cog.
- Then, align the end of the chain with an opposite link (outer and inner links) and attach two rivets of chain length.
- Break the chain with a chain tool at this rivet and fasten using a connecting pin or link.
- Once this chain length has been routed correctly through the derailleurs and the ends have been connected, the tension should be adequate. This should be the case even in the “big-big” and “small-small” gear combinations.
Should there be sagging still, you might have a problem with the rear derailleur itself and cannot tension the chain properly because of that. Thus, professional repair or replacement may be required. If the spring that pulls back the derailleur cage is worn out, repair should be out of the question. However, a new derailleur should have your bike up and running again in no time.
How Do I Fix the Chain on My Single-speed Bike?
In bicycles without derailleurs, there’s usually an alternative mechanism for tensioning the chain. This may come in the form of sliding dropouts, a dedicated chain tensioner, horizontal dropouts, or eccentric bottom brackets.
Sizing the chain correctly in these bikes calls for adjusting the tensioning mechanism so that it’s in its loosest position. When the rear cogs and chainring are closest in the distance, that’s the position you’re looking for. Then, follow the steps you learned for sizing and tension adjustment in bikes with derailleurs.
A loose chain can impact your cycling experience in some of the worst ways, so make sure you know how to deal with it. In case you don’t, then it’s probably time for a replacement.