Join Date: Apr 2009
Location: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
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Usually you see skipping on the smaller sprockets not the larger ones. That's because they're typically used more, and with less teeth are more sensitive to chain stretch. I've start by assessing the chain's condition. Measure it for stretch. It's very rare that chains stretched less than 1% (1/8"/12") skip (assuming it's the original chain), so that would give you some idea of what you're looking at. OTOH if the chain is stretched about 2% or so, you can be pretty assured that the cassette is also toast. As for the chainrings, usually wear enough to skip is clearly visible as a sharktooth profile, so if the teeth seem symmetrical you're probably OK there.
Other possible causes of skipping include stiff or damaged chain links, bad RD or hanger alignment, and RD upper pulley riding to close to sprockets (makes sense since your problem is worse on larger sprockets).
Assess the chain's condition, and eyeball the pulley/sprocket clearance, and that will give you some ideas without spending money on trial and error approaches.
BTW- lubing everything as Zippy suggests is cheap and can't hurt so you might as well.
An ounce of diagnosis is worth a pound of cure.
“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin
“One accurate measurement is worth a thousand expert opinions”
- Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance