Sorry if this has been brought up before but i found this really useful site & hope it might help other Micra owners too.I was looking at putting 13 inch steels with 155/70/13 tyres on my K10 to replace the standard 12's.
It wasn't till i used the app on http://www.carbibles.com/tyre_bible_pg4.html
That i learnt just changing from 145/70/12's to 155/70/13's(a size that was on a lot of models anyway)that when my speedo would read 70mph i'd actually being 76mph.I played about a bit trying different 13 & 14 inch tyre sizes & the changes could be enough to get you in trouble with a speed camera.
The site also has some really good info on offset/insets etc.
Obviously if the speedo is out your odometer will be too.
It wasn't till i used the app on http://www.carbibles.com/tyre_bible_pg4.html
That i learnt just changing from 145/70/12's to 155/70/13's(a size that was on a lot of models anyway)that when my speedo would read 70mph i'd actually being 76mph.I played about a bit trying different 13 & 14 inch tyre sizes & the changes could be enough to get you in trouble with a speed camera.
The site also has some really good info on offset/insets etc.
Obviously if the speedo is out your odometer will be too.