At Harold's Used Auto Parts Inc in Philadelphia, PA, we’re focused on keeping your car, truck, or SUV running well - but we’re here to keep it looking good too. Here’s some information on wheel sizing, to help you make sure your new wheels will fit your vehicle.
Width and Diameter - This one is pretty easy. The width is how wide the rim is, as in the depth. The diameter is a measurement across the face of the wheel. So, for example, if a wheel is 17X6.5, it’s 17 inches in diameter, and 6.5 inches wide.
Center Bore - The center bore of a wheel is how big the hole in the middle of the rim is. That seems inconsequential at first, and sometimes it is. However, a wheel with too small a center bore won’t mount to the vehicle and simply won’t work. In many instances, as long as the hole is big enough, it doesn’t matter what size it is - but you need to know if the rim is “hub-centric”, or if your vehicle is designed for a hub-centric wheel. Hub centric wheels fit the hub perfectly - they are designed for the center of the rim to bear the weight of the vehicle, not the studs and lug nuts themselves.
Bolt Pattern - The bolt pattern describes how many holes the rim has for the studs to go through, and is pretty obvious - if your wheels have five lug nuts, you need a five-bolt pattern wheel. What’s less obvious to the eye is how far apart those holes are spaced. If your bolt pattern is a 5X4.5, a 5X4.75 wheel won't work. You need a wheel that has 5 bolt holes, each spaced 4.5 inches apart, measured center of the hole to the center of the hole beside it. It’s important to note here that that measurement can be in millimeters or inches - a 5X4.5 is the same bolt pattern as a 5X114.3.
Offset/Backspacing - Just because a bolt pattern matches, doesn’t mean the wheel will work. Backspacing and offset are two measurements that determine how far inward the rim sits. At zero offset, the hub on the vehicle contacts the mounting point on the rim at the center of the rim. A positive offset means the mounting point is towards the outside of the wheel, and that the wheel will sit further into the wheel well. The negative offset is the exact opposite. Measuring offset means finding the distance between the center of the wheel and the mounting point, expressed in either positive or negative numbers. Backspacing is a simpler concept with similar implications. Backspacing is the measurement from the edge of the rim to the mounting point, on the backside of the rim. If the backspacing is is too high, the wheel will contact suspension and other components. If it’s too low, the wheel will stick out further from the vehicle.
Finding new rims can be daunting, but if you measure and double-check everything, you can find the perfect set of wheels for your vehicle. Or, you can let us do it - we can source the perfect wheels and tires for the exact look you’re going for. No matter your maintenance, repair, or customization needs, we’ve got you covered. For the best automotive service shop in Philadelphia, PA, call or stop by Harold's Used Auto Parts Inc today.
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