what is rear speacing

Here's the toll free number for The Tire Rack. They will be able to give you the specifics on your Vette:888-541-1777 ... But just to get you up to speed here's an explanation of spacing. Hope it helps, good luck: "Wheel Offset, Rear Spacing and Wheel Measurement Rear spacing (or backspacing) is the distance between the wheel's inboard edge and its mounting pad. It can be measured by using a ruler and a straightedge set across the backside rim of the wheel. Offset is the distance from the wheel center to its mounting surface. To find offset, plug the rear wheel spacing and width into this formula: Offset = Rear Spacing — Total Wheel Width 2 If you have a "positive" offset, the mounting pad is in front (or outboard) of the rim centerline. This situation most commonly occurs on front-wheel-drive applications. To picture this more accurately, think of the convex design of many wheels found on front-drivers; the center of the wheel sticks out further than the edges of the wheel. If there's a "negative" offset, the mounting pad is behind (or inboard of) the rim centerline. This is typical for most standard rear-wheel-drive vehicles and "reversed" rims. Sometimes, this style is referred to as a "deep-dish" wheel. For example, an 8-inch wide, 3-inch-rear spacing wheel would have a 1-inch negative offset. Conversely, if the same 8-inch wheel had a 5-inch rear spacing, it would then have a 1-inch positive offset. Finally, if the same wheel had a 4-inch rear spacing (which is exactly half its width) then the wheel would have what's known as a "zero offset." In wheel-measurement designations, the diameter is listed first, followed by the width. A 16x7-inch wheel has a diameter of 16 inches and a width of 7 inches. Diameter is measured where the tire rests, not from lip to lip."