Honestly you are going to want to keep atleast a profile of atleast 45 on the tires... If I were buying some then personally I'd go for what the 2005 STi tire size is (235/45/17)... Or possibly 245/45/17... A profile of 40 or below starts to present problems if the person installing the tires isn't good with low profile tires... They can scratch up your wheels and all sorts of nasty stuff... That happened to me when I was getting 225/45/17's installed... But that was because the installer was a douche bag n00b... Seriously though... Just remember that the rim width is 8" not 7.5" like stock... So the smallest tire size you'd want to do is a 225/45/17 and the largest would be 245/45/17...
Good luck deciding
~ Chris
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2020 Subaru Outback Touring - Wife's first Subaru
2005 Volvo V70R - 5-cylinder love! :Heart:
** SOLD **1998 Subaru Legacy 2.5GT Wagon - MOST RELIABLE car I've ever owned
** SOLD **2006Subaru WRXSTi (Former "
Boxer4Racing.com /
Continential Tire" STi) - Built EJ22t block / EJ207 JDM STi "big port heads" - 9,000rpm MONEY PIT!!!
** SOLD ** 
1995 "Tree-Hugger Green" SVX L AWD(5 MT) --- "Gumby" 130K miles
#399 in MY95, my original love...