15" to 14" rims

[*MAD DOG*]

I had 15" inch alloy mag rims on my Yaris, I purchased a set of 14" stock steelies from a member on here who had them on his 09 Yaris. I've since put them on my car. I've found that by going from 15" to 14" has caused by speedo to be incorrect. My speedo says i'm going faster than what I really am.

e.g.

To go 100km/h i need to travel at 108km/h on the dash speedo
To go 90km/h i need to travel at 99km/h on the dash speedo
To go 80km/h I need to travel at 88km/h on the dash speedo

So you won't get into trouble for speeding if you follow the dash, but you will wonder why the whole world is passing you. Of course the other bummer is if the car thinks it's going faster than it actually is it is also putting more km on my dash display than necessary and also means I have to service sooner to keep my warranty.