No idea, it's all to do with the total diameter of the wheel, so you might find there isn't too much in it, as I suspect the 16" rim has a taller tyre on it than the 17".
_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball