  Radio pulsars are often used as clocks in a wide variety of experiments.
Imperfections in the clock, known as timing noise, have the potential to reduce
the significance of, or even thwart e.g. the attempt to find a stochastic
gravitational wave (GW) background. We measure the timing noise in a group of
129 mostly middle-aged pulsars (i.e. characterstic ages near 1~Myr) observed
with the Parkes radio telescope on a monthly basis since 2014. We examine four
different metrics for timing noise, but it remains unclear which, if any,
provides the best determination. In spite of this, it is evident that these
pulsars have significantly less timing noise than their younger counterparts,
but significantly more than the (much older) millisecond pulsars (MSPs). As
with previous authors, we find a strong correlation between timing noise and
the pulsar spin-down rate, $\dot{\nu}$. However, for a given $\dot{\nu}$ there
is a spread of about a factor 30 in the strength of the timing noise likely
indicating that nuclear conditions in the interior of the stars differs between
objects. We briefly comment on the implications for GW detection through pulsar
timing arrays as the level of timing noise in MSPs may be less than predicted.
