My excuse for the bike is the standard level of potholes which are mandatory in Kent, especially on the purposely - designed rat-runs in the four lanes to avoid the Highgate traffic lights here!
When the average KCC pothole - or drain grating - is about two inches deep, the 20" wheel of the bike goes down one side, then often doesn't like coming up the other, so the Growsterbum gets a jolt every fifty yards or so! The language along Rye Road is sometimes quite interesting!
'Law of sod' says that when a cyclist approaches one of the potholes or sunken gratings, a bus or lorry is ready there, trying to overtake, so the noise can be quite excruciating...
But it does help to take a few calories off into the bargain!