Clip-on computer like a Cateye Astrale 8? You might have a bad connection.
Velo 8, possible but the elpased time was correct (compared to my HRM watch), however it does keep the stopwatch going a few seconds after stopping.
11.1 +/- 0.2 and 11.6 +/- 0.2 aren't very different. If the true value was 11.35 then they agree
I have over 200 entries in bikejournal of it being 11.6km +/- 0.05km. Never below 11.55km.
The first cycle computer I had got confused when I went under some power lines ... does yours do the same?
No power lines, however I do go under several sets of powered railway tracks (just south of Victoria). But the route is the same one I've done 200 times. If this was a factor then I would have expected to have seen it at least once before.
my commute has also shrunk, from 14.8km to 14.4km. I have noticed that traffic has been lighter recently, so I put it down to less weaving in traffic.
I don't have to weave much at all as I commute along relatively (for London anyway) fast roads, and last weeks commutes were no different to normal, certainly not 400m worth.
Could the computer have reset the wheel diameter to its default?
No, I checked it before making the original post. It's set to the right value for my tyre size. I then checked it again after another "short" commute.
It's back to 11.61km today, still on the same wheel size setting of 210cm.