gears skipping under load

[gregcampbell]

Why do my high ratio gears slip when I'm out of the saddle, but behave perfectly in the saddle?

[ColinOldnCranky]

Have you changed your chain recently? Or, failing that, your rear cluster?

[RonK]

Most likey your chain and cassette is worn out.
Also a new chain on a worn cassette will often slip.

[Duck!]

You're putting more load through when standing, uncovering issues with excessively or unevenly worn components.

If you tend to use those gears less than the mid- & lower-range gears, those sprockets will be less worn, and the worn chain will not mesh nicely. You may also notice a rumbly, gritty sensation when riding those gears while seated; the chain isn't meshing well, but in that position you're not overloading the chain/sprocket interface to cause it to slip.

[Nate]

as above worn components...

or.... does it click or make noises when not under load?
if its clicking when not under load, then the deraileur could be *slightly* out of alignment, which on high gears could be caused by a frayed shifter cable.

Open the brakes up, apply brakes & have a look inside to check that too.

[kb]

as above worn components...

or.... does it click or make noises when not under load?
if its clicking when not under load, then the deraileur could be *slightly* out of alignment, which on high gears could be caused by a frayed shifter cable.

Open the brakes up, apply brakes & have a look inside to check that too.

Alignment issues can also be caused by improper cable path in the cable clamp (there’s a clear park tools video on it somewhere - I’ll chase it up if I remember)

[rowdyflat]

if they are jumping higher then prolly derailleur cable slt stretched turn doodah anticlockwise.
jumping everywhere bent derailleur hanger ?