"Plus-sizing" or "Upsizing" is one of the most common automotive modifications. Upgrading from factory 17-inch wheels to aftermarket 19-inch wheels drastically improves the visual stance of a vehicle. However, bolting larger metal wheels and wider tires onto your car initiates a chain reaction of physics that alters how the vehicle drives.
The Pros: High-Speed Cornering Grip
When you upsize a wheel, you are mathematically forced to use a tire with a lower profile (shorter sidewall) to ensure the whole assembly still fits in the wheel well. A shorter sidewall is inherently stiffer. When you take a sharp corner, tall sidewalls tend to flex and roll over upon themselves, making the steering feel mushy. Low-profile tires resist this flex, translating steering inputs instantly to the road and providing significantly higher cornering G-force thresholds.
The Cons: Unsprung Mass & The MPG Tax
Unfortunately, metal is much heavier than rubber and air. A 19-inch wheel with a thin tire almost always weighs significantly more than a 17-inch wheel with a thick tire. In mechanical engineering, this added weight is called rotational mass.
- Acceleration & Braking: Your engine has to work harder to spin these heavier wheels, quantifiably slowing down your 0-60 MPH times. Similarly, your brakes must work harder to stop that spinning mass, increasing stopping distances.
- Fuel Economy Destruction: Heavier wheels combined with wider tire contact patches dramatically increase road friction. In independent tests, upsizing a car from 15-inch standard wheels to heavy 19-inch wheels resulted in a brutal 10% drop in overall MPG.