Middle gears - shifting issues

[Twenty Times]

I am going to get into more depth with the bike tonight - but looking for some advice before I start.

I changed my gear cable about 75 miles ago. I had the bike shifting excellent without issue. The last couple of rides, I have been experiencing issues with the middle gears (4-5-6 from the bottom; small cog). The bike is clinging and clanging and it feels as if it miss shifting. This ONLY occurs when there is pressure on the pedals.

*I checked the chain for wear (Park CCT) and its fine.
*The cassette is in good shape.
*I lubed the cable and housings when installing the new cable.

Could I be experiencing "cable stretch" because the new cable is beginning to wear?

I was planning on tightening the cable... If I do this, should I first tighten the barrel adjustment virtually all the way (or 1/2 turn or so from all the way), so I can loosen it from the barrel?

The bike is shifting SUPER smooth from all the other gears which is strange to me. The gears in question seem to "clang" - and just those gears. I take very good care of my bike and the chain has been deep cleaned and lubed off the bike with chainsaw oil. The bike has not been dropped and the hanger has not been put in danger of bending.

I am trying to get the bike race ready for November and I need the bike to be a non-issue. Any suggestions?

[DaveM]

It wouldn't be unusual for the cable to have stretched a bit. If so, you should only need to tighten the cable a very small amount. Maybe a minor turn of the barrel adjuster.

[Twenty Times]

Well - I have much bigger fish to fry!

I took off the chain stay protector (to clean the dust out) and BAM! The chain stay is cracked. It happens, but this is the second time and it is the SECOND time and in the same exact spot as last time.

[JohnnyCO]

Chain stretch could be it. tighten cable. Also check your derailleur hanger to make sure its straight.