Interesting. I’ve just swapped from 215 to 225, but didn’t even think to check the speedo, as just use the one on my radio. (More accurate and easier to see). So Fiat fiction may be more realistic now.To counter that Landy Andy , we increased our width of tyre by 10 (215 to 225) without increasing or decreasing the profile.
Not only did that make our speedo almost bang on but also increased our Tyre Load Index.
Result all round.