Don't know about 17's bein piss poor on track mate....you've found this when and with what tyres??!! I ran 15's and r888's for the last couple of years and bit the bullet and put r888's on my 17's and think there's a definate improvement over the 15's. Car handles really well, has improved traction out of tight corners/chicanes and generally seems to corner flatter. Of course this is just my opiinion/findings, also found it a pain altering the ride height settings etc when i swtched from my 17's to 15's for track.