Bike making random noises after being lubricated

Question

I bought a second-hand bicycle two weeks ago. Everything seemed to work like a charm; smooth rides; no noises whatsoever. However, lately I decided to oil it. I think that I put excessive amounts of oil in the cassette and derailleur. I used Liqui Moly 1613 MoS2-Rust Remover.

Right after the lubrication, the bike started to make a random noise while coasting. The noise is random, it doesn't appear periodically, but it is there and it kicks in let's say several times in a 1 minute span. It sounds like cracking joints (bones), but a little bit more intense and sharper. Nonetheless, the ride was still smooth.

I didn't have the chance to ride it again after the first trial after the lubrication.

I hope you can give me some insights regarding the possible problems my bike might have. Can it be just because of the excessive lubrication? Is there any risk if I continue riding it like that, given that the ride seems super smooth still?

Edit:

I rode the bike after I came back from vacations, and the noise is not present anymore :).

Answer 1

First, what you have is a bike with derailleur gears. The derailleur itself is the mechanism that moves the chain onto one of several sprockets mounted on the rear wheel hub to achieve different gear ratios. The sprockets can be referred to as a sprocket cluster. Many people also call it a cassette (although that properly refers to sprockets mounted in a particular way).

The sprockets themselves do not need lubricating, only the chain does. Excessive lubrication can be dangerous if oil gets on the tires, braking surfaces on the rims (or discs on new bikes) or brake pads. It also tends to make a nasty mess, getting on the frame, wheels, legs and clothing.

What I would do is give the bike a good clean, using a degreaser product to remove the excess oil on the sprockets and chain. There are decent citrus based ones available that work well and are not expensive. There are many Youtube videos out there that will show you how to properly clean a bike including the sprockets and chain (example below).

Buy some bicycle chain specific lubricant and re-lube the chain. Bike chain lube may seem expensive but it lasts a long time because you only need a drop on each joint in the chain.

From you description it's hard to say what's causing the noise, but it seems likely it's connected to the freewheel ratchet mechanism if it only occurs when freewheeling. I doubt it is due to excessive oil on the sprockets. If you are not mechanically inclined I'd have a good local bike repair shop check the rear wheel. Even if the noise isn't dangerous it's super annoying for a part to break on a ride and leave you stranded.

Answer 2

As Argenti said, it's hard to say what's causing the noise. Here is a way to narrow down some possibilities.

Since the noise happens when coasting one might guess it's coming from the rear wheel.

1. Pop the rear wheel off
2. hold the freewheel side of the wheel axle in your right hand
3. the other end in your left hand
4. give the wheel a spin using your fingers to push the spokes away from you.

If the noise is coming from the axle you'll hear it.
If everything is quiet, with your thumb hold the freewheel still.
If the noise is coming from your freewheel or something rubbing on your freewheel you should be able to hear it (if you hold the freewheel side of the wheel axle in your left hand you might injure your thumb).

If you can't find the noise after experimenting with the wheel off the bike then either the noise only happens under load while coasting or it's coming from some other part of the bike.

My guess is that Argenti is correct and it's coming from the freewheel and you will hear it when you hold the freewheel still.
Let us know what your testing uncovers so we can attempt to be more helpful.