Vengeance kit won't work on official timing

Moav

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Nov 22, 2010
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I've got asus m5a97 v2.0 board and recently acquired Corsair 4x4GB 1866mhz 9-10-9-27 set.
Long story short, after trying different methods of testing I've found out that what made memtest pass the test was lowering the timing to 11-11-11 from the official timing approved by Corsair.
Well, question is, how come it won't work on the approved timing?