Gears Slipping

[DuncanBeaumont]

I recently removed my rear wheel to fit a new tyre. The gears now slip a small amount from time to time. I haven't made any adjustments, that I am aware of.

How can I rectify this? Any ideas please?

 

[Moodyman]

Double check that the rear hub sits properly in the drop out.

Slight misalignement can throw your gears / brakes out.

Whenever I remove and reinstate wheels, I do them when the bike is upside down so that I the wheel is sitting properly.

 

[numbnuts]

If not the above
free hub worn, pawls sticking
worn chain
worn cassette
worn chainring