linberl

So - I had a very quiet Bike Friday. I decided I needed to change the gearing so I replaced the cassette (it had an 11-30 HG 30 and I put on a HG 50 13-30 since I never ever used the hardest gear). At the same time, I changed the chain. It had a KMC Z51 and I read that the KMC x8.93 was compatible so that is what I used. Number of links kept the same. I also tried an SRAM pc 870 and had the same noise.

Now, I have a buzz off the rear derailleur that gets louder the faster I pedal. It is not the same as the sound of the pawls when I coast, it is higher pitched.
Also, there is a clunk/clink coming from somewhere. I noticed it every time I get on the bike and begin to pedal. It then happens intermittently, not rhythmically, when riding. Usually when I speed up after coasting or slacking off a bit. Sometimes, but not every time, I feel it in the pedals, particularly the right side. I don't hear it pushing up hills.

What I have tried: I removed the pedals, cleaned and regreased them and reinstalled. I removed the seat post and regreased it and reinstalled. I had a bike shop make sure my rear wheel was properly in the drop outs. I removed both jockey wheels and cleaned them and reinstalled with a bit of grease but I did not touch the bearings.
The cranks don't feel loose, but I'm a wimpy old lady so maybe I can't pull hard enough. I have no idea how to check a bottom bracket. I don't see any stiff links and I've lubed the heck out of the chain. I'm kind of at the limit of my mechanical knowledge, which wasn't all that much to begin with, lol.

Do I throw in the towel and take it to a shop? What would I tell them so they don't end up taking the bike apart and charging me a fortune that I can't afford? Any particular things to check in a certain order?

Thanks, appreciate any help on this, as the noise is making me crazy. Now I'm sorry I changed the gears :-(

2lo8

Did you change the parts yourself?

Cassette lockrings should be very tight, 30 foot pounds. If you were using a small 6" wrench, that would be 60 pounds of force. And you should make sure it's not missing any spacers.

The derailleur may also need to be readjusted after changing cassettes. The B screw makes sure that the pulley wheels on the derailer don't touch the cassette which increases noise. Cable tension being off means the chain might not be centered over cogs, which can cause the issue you describe.

Another possibility is a kinked chain link as you said, but you said you couldn't find any.

Sometimes new parts are just a bit noisier until they wear in.

linberl

Yes, I did it myself. The HG 50 came with a very thin spacer which I put underneath the lock ring (seemed that is where it went per the instructions). Without it, the one cog not riveted moved around, once I put in the spacer and tightened it, everything seemed rigid. The previous cassette had no spacers on the hub end.

I followed the adjustment for SRAM derailleurs on the Park Tool website and, while it may not be absolutely perfect, the high/low screws are spot on and the cable tension seems good. The B screw is set 6mm from the biggest cog, again, following the video. It shifts pretty much like it did prior to the swap. When I look at the chain, every other tooth is dead center on the pins. It has an alternating offset apparently. I also sighted the pulleys/chain/chainring and they look to be in a line. I've ridden about 120 miles since the change out.

2lo8

There normally isn't any spacer under the lockring. Sometimes just a very very thin washer attached to the lockring that you could easily flex with your fingers, but it should have no effect on the ability to tighten the cassette. Sometimes you find a spacer between the loose cogs and the cluster and other loose cogs. Otherwise spacers should go behind the biggest cog.

linberl

I guess it is a washer, not sure what to call it. Definitely very thin and extremely flexible. It did make a difference when I tightened the cassette in that the smallest cog had a tiny bit of wiggle without it. The rest of the cassette is riveted. It didn't affect the ability to crank it tight but seemed like it was just the extra bit needed to secure the small cog perfectly.

I'm wondering if there is some protocol that will help me isolate the noises? I do not hear them when I roll the bike, only when the chain is turning, so it has to be connected to the rotation somehow, right?
Did I mention it is making me crazy, ha ha? Thank you for trying to help =)

2lo8

I can't tell without a picture, but the lockring washer is a very thin sheet of silver metal. It's so thin it should have no effect on tightening. It appears some 7 speed HG-50s have a spacer that is not a round circle between the loose cog and the cluster, but that would still only cause problems in that gear.

Another thing, jockey pulleys are often top/bottom specific and undirectional. Either of these issues can cause noise, but you mentioned that you only did this after looking for the noise. You might also want to check if the chainring bolts are tight. QRs too, everything you touched when swapping parts. You can feel if cranks have play by pushing and pulling the crank arms towards and away from the frame. Often times once you've isolated the general area it's easier to just go over every bolt than try to guess. The problem is noises when pedaling could be anything because the bike undergoes slight side to side movements and everything you touch while pedaling can also make noises.

linberl

If I take the new cassette off and reinstall the old one, would that help to isolate the noise? If it still happened, I would know it is not the cassette. If it stopped...at this point I would just leave it on and maybe consider having a shop do the swap out. Or am I missing another potential factor?

2lo8

Or anything you touch when you change the cassette, which would mostly be the skewers and the lockring.