Staggered 20x8.5 & 20x10 ET 15

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Does anyone have this wheel setup on the M37?
Staggered 20x8.5 ET 15 & 20x10 ET 15
I'm a little worried that they the tires will rub the fender with the offset at 15.
I have read that some used 20mm spacers with their OEM 20" wheels, but I couldn't find a definite answer.
Also, I'm thinking about using these tires:
Front: 245/45/20. Rear: 274/40/20
I know the speedo will be off by about 3% slower, but I want more sidewall.
Thanks.

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If your car is lowered I think those tires will rub. Mine with the Eibachs, and 20 Offset 20x10 rear wheels is running 275/35 20...and it's close but never touches. I think one step up on the sidewall will touch when the suspension compresses.