The larger the cog your bike chain is sitting on, the lower its gear. Unfortunately, sometimes a bike chain makes noises that are specific to these lower gears, and it can be challenging to pinpoint what is causing them.
However, it’s easier to troubleshoot when you can narrow it down to a gear-specific problem. Why does your bike chain make noise in low gear?
The main reason why your bike chain makes noise in low gear is that you’ve switched to a cassette with a larger low gear. The upper derailleur pulley is too close to the new cassette, and now the chain is rubbing where it shouldn’t. You can fix it with an eighth to a quarter-turn of the B screw.
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Why Is My Bike Chain Making Noises In Low Gear
The only thing more frustrating than a bike chain that is making noises is one that only sometimes makes noises.
It can take time to realize that the chain is only audible in low gear. Unfortunately, the longer it takes to discover a problem, the more likely it is to cause damage or make the existing troubles worse.
It is crucial to know why your bike chain is making noises in low gear so you can fix it immediately.
It doesn’t take very long before a rubbing chain becomes a stretched-out chain. Metal on metal is pretty unforgiving, and any part of your bike the chain can make noise against is also made from metal.
At best, you’ll catch it early, but at worst, you can end up with a mangled chain that gouged a deep line of damage into another part, and then you have to replace two pieces.
The list below has the most common issues that cause a chain to make noises in low gear.
1 – B Screw Is Set Wrong
Switching over to a cassette is common for people who work on their own bikes.
Even if a professional swapped the parts at a shop, the larger low gear could still cause a rubbing issue, and that will make noise.
You should never ride a bike that is making a weird chain noise since it indicates something is wrong.
Adjusting your B screw by an eighth to a quarter turn will often fix the issue. However, you may also need to turn the upper and lower screws as well to get the proper angle and alignment.
Remember to turn each screw a minimal amount at a time, so you don’t miss the mark.
2 – Quality Control & User Error During Assembly
There are fifteen to twenty million bicycles sold per year worldwide. That means the factories where they are made are cranking out huge numbers of parts, and some assembly issues are bound to arise.
For example, a badly adjusted derailleur can cause chain rubbing in lower gears and make a weird noise. Accidents happen.
Moreover, many bicycles are not assembled at the factory. Resale shops and big-box stores sometimes assemble parts into bicycles themselves, but so do individuals.
If you got your bike in pieces in a box, and it makes a funny noise in the lower gears after assembly, the first place to look is that derailleur. You’ll have chain noises in low gear if it is set just slightly wrong.
3 – Backward Chain
Not all chains have a direction, but some do. If you install a new chain, always check to see if it’s directional.
After all, even experienced bike mechanics can make a minor mistake like this and set a non-reversible chain backward simply because they are used to it not making a difference.
Chains can have an inside and an outside.
However, as Bikes Stack Exchange explains, “If you have such a chain, you’ll need to make sure that the inside is inside. You can still reverse its direction though, unless it is also directional, i.e there is a left and a right (the second exception).”
4 – Binding In The Rollers Of Your Chain
The lower gear doesn’t cause chain roller binding, but it might be more noticeable to you because of the larger cog size.
Typically a chain binds when it’s overly tight around your sprockets and doesn’t have enough play or wiggle room to move smoothly.
Because the sprockets don’t wear evenly, a chain can be substantially tighter around one spot than in other areas.
The practical and straightforward solution, in this case, is to replace the worn-out part. However, you should always inspect the chain itself as well.
Unevenly worn parts cause uneven wear on other pieces as well. More often than not, you will find the chain needs repair or replacing as well.
5 – Damaged or Bent Front Derailleur
Usually, the front derailleur stays put once it’s in place. Assuming it came out of the factory or was otherwise assembled correctly, this isn’t usually the cause.
Even when there is a minor issue, the B screw will usually fix the problem, but when it doesn’t, you need to look at the derailleur closer.
Especially if you or your bike were in an accident, the derailleur could get bent. Sadly, this will result in a misalignment that isn’t as easily fixed by turning a screw.
Advanced DIYers and bike mechanics may solve this issue at home and rebend it, but if you’re concerned about your skill level, you may need to take it into the shop or get a new part.
Helpful Tips To Know About Bike Chain Noise In Low Gear
Learning to set your screws can save you a lot of trouble, especially if your bike chain suddenly starts making noise in low gear.
Experienced cyclists know that identifying strange sounds and developing the skills to repair them on the fly is essential.
Here are more helpful tips to know about bike chain noise in low gear.
- If you have a stiff chain link, you may hear it first as a clicking sound. Alternately you might feel it as a skip where the chain doesn’t line up correctly, and the links don’t roll smoothly around your gears.
- Narrowing the problem sound down to a click or a scrape can be surprisingly helpful when you need to identify the cause of a problem.
- Always carry essential bicycle tools with you when you ride. There aren’t very many tools that you need to keep your bike on the road in most circumstances. For example, carrying a chain tool with you will allow you to resolve stiff links so you can keep riding.
Identifying and fixing most noises that happen when your chain is in low gear is relatively simple. The majority of the time, it is a problem you can fix by adjusting the B screw.
However, if that doesn’t work and subsequent adjustments to the high and low screws don’t help either, then it’s either the derailleur or the chain itself.
You should be able to determine where the problem is merely by listening and looking.