I don't have an exact answer BUT if you go with a lesser diameter in the rear you should try and do the same with the front. The trick is to keep, more or less, the same percentage of change front and rear so the sensors don't send confusing information to the PCM. You have some wiggle room but if you get too far off, front to rear, you'll have trouble.

I run 18 inch rims for road racing, 245/35/18 and 275/35/18 with no trouble. Stock sizes on the street.

Les