iredell

I have a slow leak in my right rear tire (4 pounds every 15-16 days). These tires are non-runflat (the ride with the runflats was so bad, I ditched them). The tire shop blames the wheel, saying the rim may be damaged allowing air to leak out. However, my mechanic says the tires I have on the car right now are 245/45R18 instead of 245/40R18. Two questions: Could the oversized tires be causing the slow leak by not fitting the rim correctly, and What brand would any of you recommend in a 245/40R18?