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.
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.