To know for sure, you need to:
1. Check your existing rims: The size is stamped on the inside or outside of your current wheels. It will be a series of numbers like "16x7" or "17x8," indicating the diameter (16 or 17 inches) and width.
2. Check your owner's manual: This will specify the recommended rim sizes and bolt patterns for your specific Silverado model.
3. Measure your wheel bolt pattern: This refers to the number of lug nuts and the distance between them. You need to match this to any new rims. This is critical; using the wrong bolt pattern can be dangerous.
Without this information, it's impossible to definitively say whether 15-inch rims will fit. Trying to force incompatible wheels onto your truck can damage your vehicle, so always double-check compatibility before purchasing.