Nolabeng

About 2 months ago I had a local bike shop swap out the chain & rear cassette on my '98 Bianchi Campione as they were pretty worn out. Since then I've put about 400 miles on the bike.

Several weeks ago I was riding up a ramp in a parking garage, & stupidly, I downshifted "too late," after already starting my ascent up the hill. The chain & gears basically made a horrible "shredding" noise while trying to downshift.

Recently I noticed that my chain skips every 5-10 rotations while only on the highest gear(smallest cog), while I'm applying mild to heavy pressure while pedaling. My question is would that one nasty downshift I made in the parking garage possibly tear up the small cog up to a point where is would skip the chain? Just seems like they should be able to take more damage/wear tear than that. Visually I can't tell a real difference between the teeth on it & the other cogs.

Or, could it be the rear derailleur being out of adjustment or something else? I'm hoping this is the case as rear cassettes aren't cheap on my bike.

cny-bikeman

The cog is very unlikely to be damaged by that incident. It's possible a link in the chain suffered some damage that only shows up occasionally. Turn the cranks backward and look for any jumping of the chain as it hits the pulleys and feeds onto the cogs or chainwheel, also view from behind the bike to see if the chain "snakes" or has an abrupt lateral move. Also possible of course that the derailleur is out of adjustment. All of that aside it should not be common at all that you put heavy pressure when pushing the small cog.

StanSeven

Do you have the chain on the small chainring in front at the same time? Is somthat's called cross chaining. Your chain is stretched to the max and will make noise. A new chain will be especially bad because it isn't allowin the chain yo fully engage the gear teeth.