Replaced chain, bike makes grinding noise?

Question

Recently, I started going to a community bike shop to learn how to maintain and service my own bike.

Ever since I changed the old, worn-out chain to a new chain with a master link, I've been experiencing this grinding when I ride. I can feel the vibrations in my feet when I pedal and the handle bars when I have it on the stand and am examining it. The chain also jumps a lot (feels like it shifts gears without me doing anything, then stays on the same gear anyway).

The bike shop thought it might be the rear gear cog being worn out, so I replaced it and it still happens. We also adjusted the derailer, but it didn't help.

The bike shop volunteer thought it could also be the bottom bracket of the pedals. Which, upon closer inspection, seems likely...it's just weird it only started happening after I changed the chain (which they helped me size, to make sure it was right for my bike).

After looking on here, I think I'll pop off the chain and see if the pedals still make the grinding noise. If they don't make the noise, I'll try a different chain or try flipping the chain (just in case). My next step is taking it into the actual bike shop where I bought it and having them diagnose the problem.

Anyone have anything to add? I'm curious why all these problems only started after I changed the chain. Could it be something else?

Edit: we suspected the cassette was worn and already replaced that, but the problems kept occurring.

Update:

I finally made it into the bike shop again. Last time I was there, we adjusted the back derailer and I guess we didn't get it quite right. I had help adjusting the derailer again and now the chain jumping and skipping is gone!

For the grinding noise, the volunteer I talked to suspects it's the front derailer/chain guard/cogs. Something is rubbing against the chain near the pedal. I'll be working with him next time to further diagnose the problem.

Answer 1

As you have a master link, removing the chain should be easy.

My guess - you threaded the chain in the wrong way through the rear derailleur. There are a couple of metal extrusions between the rollers, intended to keep the chain from jumping.

With the chain still attached, look at the part of the RD I have tried to mark with "1" and check if the chain is rubbing against anything there.

Answer 2

"The chain also jumps a lot (feels like it shifts gears without me doing anything, then stays on the same gear anyway)."

Based on this I'm going to suggest that the cassette is worn (the rear gear cogs). If the chain was very worn it will have worn the teeth of the cogs to the same fit, now with a new chain they no longer align properly. Depending on the cassette model it is fairly cheap to replace, but does need a couple of special tools - your community bike repair group should have them. See here for GCN's how to replace a cassette. But you've already replaced that right? Make sure it's fitted correctly and is the right size - if you've switched to something with a lot of teeth on the biggest cog you may need a longer rear dérailleur.

In the future check the chain stretch frequently using a chain wear tool and replace it when there is 1% or more wear, this will prolong the life of the cogs in the cassette and chainrings (front gear cogs).

Also check the chain is threaded correctly through the drive train, check the bottom bracket by knocking the chain off and spinning the cranks, check the alignments of dérailleurs, and grease the jockey wheels.

Did you use the correct size of chain? And did you set the length of chain correctly?

Answer 3

Apart from more obvious issues like mal adjusted front derrailleur where the chain would rub against it at certain positions (this should not occur when you are using the middle rear cog)....

I once encountered a sandy gritty feel on the pedals on a bike with new but very cheap cassette and chain. after ascertaining it was not pedals (rotated the pedals alone by hand) and not the bottom bracket (I removed the chain and pedaled) I eventually found it to be the very new and very cheap cassette (we are talking those new 6 speed freewheels with the Shimano brand on the the largest cog) to be at fault. After a swap with a very old and used 6 speed freewheel (good quality circa 1979) the transmission was smooth as butter.

On another time with my first foray of replacing chains, i had incorrectly placed it on the rear derrailleur jockey wheels. It then rubbed on a metal tab as it traveled through the jockey wheels

Another time I had replaced a chain on an old 12 speed bike with a NOS 1970s Shimano chain that I think had rivets that sat too far proud that it rubbed against the cassette when one was in the taller (smaller) gears.

Recently I adjusted a brand new aluminium road bike that when the bike was on big in front and small behind, the chain would rub on a weld seam at the point where the chain stay meets the seat stay.

Another time I set the front derraileur too low and it was lightly brushing against the teeth of my crank chainring.

Answer 4

It looks like you have an 8-speed chain and rear cassette, and that you installed a fancier nickel-plated KMC chain (X8 something). If that's the case, I've had a similar problem with a bicycle with a shorter wheelbase and a 10-speed crankset.

My problem was due to the nickel-plated KMC chains being slightly wider than other 8-speed chains (7.3 mm vs. 7.1 mm pin length). With the shorter wheelbase, the chain was more frequently at a sharper angle. Due to this sharper angle it was more likely to catch on the pins and other shifting aids of the narrower 10-speed chainrings and start shifting. This setup was just enough to cause constant grinding when coupled with a 7.3 mm wide chain, as it was constantly catching and releasing from the pins of the chainrings.

Switching to a 7.1 mm chain (such as KMC Z51 or SRAM PC-830) eliminated the grinding problem. Often when you look at a new bike with a KMC chain, the chain will say "NARROW" on it. That's a 7.1 mm chain.