Sport rim is often one of the first modification any car enthusiasts will do to their car, as aftermarket rims are generally much more better looking than original rims. Other reasons being aftermarket sport rims can be much lighter, stronger, and bigger in size if one decide to increase from the stock tyre size.
When looking at aftermarket sport rims, they are measured in a few ways. They are offsets, size, width and X factor. Offset is often measured in millimeters and can be negative or positive. This measures the distance from the hub mounting to the rim’s true centerline. Positive offset being the hub-mounting surface is closer to the outside edge of the wheel, for instance the wheel wraps around the hub and brake hardware more deeply, whereas negative offset being the hub-mounting surface is closer to the inside edge of the wheel and wheel sticks outwards more than inwards. If you are to purchase aftermarket rims for your car, a wheel with too positive of an offset will be closer to the edge of the fender, and one with a too much negative offset will results in tusking inside the fender and be closer to the suspension components. Generally increasing the tyre size is perceived as an improvement from accelerating to decelerating, people also use reduced profile number, often as low as 35% to keep overall rolling radius error within a few percent of the original tyre. But user will sacrifices comfort more or less due to the shorter and stiffer tyre side wall, but benefits from better handling and higher cornering limits due the lower side wall flex.
Also if one is planning to upgrade their brakes or already did, the offset of the rim should be taken into concern as aftermarket sport rims with too high of an positive offset may result in the sport rim being unable to be installed as the bigger modified brakes will be in the way of the new aftermarket sport rim. Although generally we change our rim to bigger if not the same size as the original rim, overly wide rim may result in more vibration and less comfortable ride when compared to smaller one as the side wall of the tyre does not have efficient curvature to flex properly during rough road driving as they originally intended to do. Oversized rims will a lot of times causes tyre to rub on the body or suspension components while turning. Over narrow of a rim will result in poor handling as the tyre may distort sideways under fast cornering, while also reducing the ability of the tyre to cut through water to resist hydroplane, raising safety concern.
Finally when one is planning to change out their rim for a set of aftermarket one, be advised that altering the size of tyre will cause speedometer error, often when rims are changed to different size and tyre is changed to different thickness. These is a handy diameter formula to calculate the speedometer error though, available on the internet.
Check out the VMR V710 wheels