Bicycle Mechanics - Chain 'Popping'

I'm relatively new to doing my own bike repairs, and have come across a problem that is puzzling me.

When I have my chain on both the smallest cogs, front and back, and I begin to ride, the chain seems to 'pop' and loosen, but eventually finds it's way back on. What could this 'pop' be? Originally I thought the chain was just falling off, but that's not the case.

Any ideas?

Have you recently replaced your chain, or taken it off/put it back on with a chain tool? If it's the same spot on the chain, check for a stiff link.

Aside from that being a bad gear combination to be in the stiff link caused by a chain change is one likely possibility. If a link has cracked on one side that can do it. Find if one link is always the one that pops and twist it a bit to loosen it. If that does not work try replacing the chain and twist the join link in the new chain so it will not be stiff too. Any damaged or missing teeth in the cogs. How old is the chain? If the chain is worn and stretched a lot you will have all sorts of problems and may need to replace both chain and cogs and chain rings.:eek: .

Stiff link is my guess. Just put a new chain on this weekend and had the same thing happen cuz the pin wasn't seated all the way.

Pop occurs only in the small/small gear combo = worn small cassette cog. A chain problem would show up in other gear combinations. After you replace the cog or cassette, try to remember not to use the small cog unless you're in the big ring in front. Small/small is an easy gear to ride around in, but the small cog wears out fast.

[QUOTE=Mustangs84]When I have my chain on both the smallest cogs, front and back, and I begin to ride, the chain seems to 'pop' and loosen, but eventually finds it's way back on. What could this 'pop' be? Originally I thought the chain was just falling off, but that's not the case. [QUOTE]

The best I can figure from your post is that this is a cross-chaining issue. Small-small = Bad. Without knowing where the slip is occurring (does the resistance in the pedals disappear quickly and feet spin until it "re-catches"?) I believe that what is happening is that the cross-chaining is allowing the chain to come in contact with the shift pins on the large chainring causing a "half-ghost" shift.

If this is indeed the case then this is normal. As mentioned in other posts...avoid the small-small. Also larger-large is a bad combination although you will not have the same result, just excessive chain noise.

Search for "Cross Chaining" and you should find out more than you ever wanted to know about it.