| As anyone will tell you, caliper clearance is a function of the design of the wheel not so much the offset. However, that being said offset does determine how the rim (and yes I do mean to say rim) is positioned in the wheel well. Now we can run stock rear TT wheels (16x8.5"+38mm) up front with no problems. So for an 8.5" wheel +38mm is a good reference for the offset. So long as you choose your tire to have a similar overall diameter to the 245/45ZR16 you shouldn't have any problems with the front (outside of caliper clearance, which is a function of wheel design). For the rear another good starting point is the stock rear wheel (16x8.5"+38). Now 8.5"=215.9mm, and the stock wheel mounts 38mm to the outside of the centerline of the wheel. So measured from the mounting point the stock wheel protrudes 69.95mm. In essence the face of the rim (again using that as reference rather than the spokes) is 70mm from the mounting point. Now if we run a 18x9.5" wheel it has a width of 9.5"=241.3mm. So if we want to maintain the location of the face of the wheel then our offset should be +50.65mm. Of course this means that the extra inch of rim (again referring to the rim of the wheel) now protrudes past where the stock wheel did to the inside (which can cause issues). On the other side of things if we want to keep the inner face the same distance from the mounting point we simply subtract the added 1"=25.4mm. Thus our new offset is +12.6mm. A compromise is to allow the rim to grow evenly then we simply keep the same offset +35mm. So the 9.5" wheel will stick out 0.5" from it's current position (inside and out). This may cause clearance issues. Your best bet is to run as close to a +38 offset. You really need to test fit the wheels. At the very least see if you can get a pair of wheels in these sizes and check clearances. Also something to think about is how these wheels will look. Most of the time you want a more dished look in the rear than the front. However, offset does control that to some extent. In general if the wheels are the same width you want to run equal or lower offset in the rear so that the rear look more dished. See if you can do these: F: 18x8.5+38mm
R: 18x9.5+42mm <---try not to go larger than this offset
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