Gear Slippage

Another very basic problem - the 5th and 6th gears sometimes slip between eachother automatically… I’ve expereinces this before on other bicycles, the derailleur is secure and the gears and derailleur seem undamaged, what causes this?

This may help: … wer-gears/

I’ve had the same issue before. The culprit was a worn-out chain.

Holy crap…the bike was new 5 months ago!

Was riding my bike last week in the hills. Chain suddenly started slipping between gears. Thought it was due to heavy stress from climbing significantly sloped hills.
Got onto a flat piece of the road and kept happening and then, WHAM, the chain broke.
Never had gear slippage ever in 30 years of biking, first time, and the chain link just separated. LBS owner said couldn’t fix the chain so got a new one.
Might not be your problem, but direct your LBS guy to do whatever tensile (maximum stress that a material can withstand while being stretched or pulled before failing or breaking) test on it if possible, just to give you a slight peace of mind.

just get a new chain and be one with it.

cheaper than a new cassette.

the longer you run with a stretched chain, the more you wear the cassette too, and then eventually even a new chain will slip on that cassette. Really old chains need to be changed in tandem with the cassette.

Unlike Shimano, the Record chains from Campag last it seems forever, but by the time you change them out they have to be changed with the cassette at the same time. that’s 300 bucks right there.
So be thankful you can slap a 20 dollar KNC chain on twice a year and be done with it.

Lay down 30 bucks for a Park chain tool as well and make the switch yourself.