I’ve finally had a chance to do a proper speedo check since the new tyres went on, and it looks like my speedo accuracy has improved from (a not very scientifically-measured) 20%, to 15% optimistic. I borrowed a friend’s iPhone and used the app that shows the route you take and you can get statistics on the journey. I carefully noted the maximum speeds I achieved according to the speedo – these were 40mph on the outward journey (which came out at 34.61mph actual), and 35mph coming back (30.45mph actual).
It also seems to confirm that my top speed hasn’t increased significantly (if at all) since the change of tyres, as under the old regime I used to see about 42mph which translates to 35 when corrected by 20%. I think I have seen 42mph under certain conditions since the tyre change, which comes out at 36.5 – hardly earth-shattering!
Yes. This is pretty much identical to what I was getting, too speed-wise. Those tyres are great, though, aren’t they! So nice to be able to chuck the bike about a bit with so much more confidence