Hi Nigel, Interesting, I've had problems with heat. My speedo is accurate and I've never had problems until the hottest days of last summer when after a few miles it would bounce around for a few minutes then just stop reading. It has worked perfectly since so I'm putting it down to the heat. I've ordered the extra ground as detailed in your link above but have not got round to fitting it yet as hot days are not normally an issue in Scotland!