From what I've seen, Discount Tires has access to a few tires that no one else can get. It works both ways, though, because I have gone to them for tires that they told me they couldn't get.
Also, I agree with d0sitmatr... I actually regret not getting slightly taller tires. I only lost 1% with my current setup, but still, I would have rather gained 1% (basically 9 less revs per mile). Especially with my car, where freeway cruising speeds just put me into boost with my turbo (hurting economy).
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