[Boxster44]

I have to disagree with this group.... 18s are faster - maybe 1/2 second (AX reference). Better response.... and not necessarily heavier (combo of wheels and tires), depending on what you buy.

However, the economics mentioned are a real concern.... several hundreds more for tires.

Just reread your question.... smaller (tire) diameters will likely help your gearing in AX and may require gear changes at inopportune times at the track (depends on the track).

good luck,

kj