When I ordered my new wheels, I went up a tyre size as they were 1/2" wider and I like to reduce the prospect that someone might kerb a wheel, so more rubber=more protection.
After checking out the circumferences, I went with a 235/55 which was slightly taller than the original 225/55 but almost the same as the 225/60 size that is fitted in the US.
Today, with Cruise (ACC off !) set at 100km/h I tried the GPS speed function on my phone and on a straight and flat road, it fluctuated from about 99.5 to 100.7 or so. Certainly going to a 235/55 if anything has made the speedo more accurate than it used to be !
I am liking the new tyres which although I didn't find the standard ones noisy, seem a little quieter. Thing is, how can you go wrong with a tyre that has a model number of KL15 anyway ?