I've been doing some figuring while trying to figure out what setup I want for winter wheels and tires. Using the standard and sport package setups, I calculated the distance from the mounting surface to the outside edge of the tire (let's call that 'd'). So here's some math that may help you figure out what you want:
Standard Front (18x8, offset +43, 225/50R18)
d = 225 / 2 - 43 = 69.5 mm
Standard Rear (18x9, offset +15, 245/45/R18)
d = 245 / 2 - 15 = 107.5 mm
Sport Package Front (19x9, offset +47, 245/45R19)
d = 245 / 2 - 47 = 75.5 mm (6 mm further out than standard wheels and tires)
Sport Package Rear (19x10, offset +30, 275/35R19)
d = 275 / 2 - 30 = 107.5 mm (same as standard wheels and tires)
So just decide how you want your wheels to look relative to the standard or sport package. For instance if you want 245s in the front and 275s in the back and you want both front and back to sit 1/2" (13 mm) further out than the sport package, you should be looking for:
New Front Wheels (19x9, 245/45R19)
245 / 2 - 75.5 - 13 = +34 offset
New Back Wheels (19x10, 275/35R19)
275 / 2 - 107.5 - 13 = +17 offset
Hope that helps. Of course, I just made all that up so if anyone sees a flaw in my logic feel free to correct.
Also keep in mind that the bearings have been designed with the center point of the tire contact patch at a certain location relative to the mounting surface so the further away from that point you end up, the more stress there will be on the bearings.
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2010 Carbon Silver / Persimmon, Touring 6MT + Sport + Nav + Tint
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