Another method of upgrading is the purchase of bigger wheels and tyres, within the safety limits set by the auto makers. The primary goal of most people who engage in this upgrade would be for the aesthetics of the car, with improved traction, safety and handling being complementary benefits. These are nonetheless tangible benefits so this method kills two birds with one stone!
From the above simple analysis, readers may be tempted to think, isn't the second upgrade a better option with all the improvements of the first option, as well as improving the profile of the car? While this may seem that way on the surface, the tradeoff for bigger wheels would be an increased body weight, and greater traction due to their increased width, both having an adverse result on the vehicle's acceleration (another aspect of performance). The second option is also more expensive, as more and better materials are required in the production of bigger wheels and wider tyres.

New vehicle owners should not rush to upgrade their factory wheels, as the new tyres that came with the car represent an irretrievable sunk cost. Instead, consideration should be made on whether you can accept the factory tyres’performance in the interim. Upgrading the tyres can be fully explored when the tires need replacing.
One should consider the vehicle's horsepower (hp) before deciding on upgrading the tyres. If the hp is low, it will not improve performance by enlarging the wheel size. For example, a great majority of cars in Malaysia fall into the 1.6 to 1.6 liter passenger vehicle category. Most cars in this category weigh 1 to 1.2 tons and make between 115 to 135 hp, and use 185/60R14 tyres. In these cases, some performance gains may be actualized if the tyres were changed to 185/65R14, or if the width was reduced to 175mm. However, most owners choose instead to change to 195/50R15 or even 195/55R15, which only serves to increase weight and subsequently fuel consumption.
Conversely, if your vehicle's hp is above 200, changing the tyre's size and width may serve to improve handling due to the increased traction.
After you have decided to upgrade your tyres, you should do some research. What the best tires within your budget are, what the leading brands are, and which tread designs you prefer. Generally, the heavier the tyres, the more beautiful and deeper the tread designs, thereby increasing traction.
To a car owner, the most important thing is, what is the biggest wheel size that can fit into a vehicle. There is a simple rule, which is the upgraded wheel's diameter should not be larger than 3% of the original. For example,
If we take the 185/60R14 specification as an example, with the original diameter size as follows:
Wheel diameter: 14 inches, 14 inch ×2.54 centimeter =35.56 centimeter
Sidewall: 60% of the tyre's surface, 18.5 centimeters ×0.6=11.1 centimeters
But as each wheel has two sidewalls, the sidewalls have to be multiplied by 2,
Sidewall: 11.1 centimeters ×2=22.2 centimeters
Diameter: 35.56 centimeter +22.2 centimeter =57.76 centimeter
Is it possible to upgrade to a 195/50R15 tyre?
Wheel diameter: 15 inches, 15 inch ×2.54 centimeter =38.1 centimeter
Sidewall: 50% of the tyre’s surface, 19.5 centimeters ×0.5=9.75 centimeters,
As before, as each wheel has two sidewalls, the sidewalls have to be multiplied by 2
Sidewall: 9.75 centimeters ×2=19.5 centimeters
Diameter: 38.1 centimeter +19.5 centimeter =57.6 centimeter
Compared with the 185/60R14 specification tyre’s diameter of 57.76 centimeters, the difference is only 0.3%, which is well within the allocated range.
But what if we just increase the tyre surface without changing the thickness of the sidewall that is using a 195/60R14 tire?
Wheel diameter: 14 inches, 14 inch ×2.54 centimeter =35.56 centimeter
Sidewall: 60% of the tyre’s surface, 18.5 centimeters ×0.6=11.7 centimeter again ×2=23.4 centimeters
Diameter: 35.56 centimeter +23.4 centimeter =58.96 centimeter
Compared with the 185/60R14 specification tyre’s diameter of 57.76 centimeters, the difference is now 2%, which is basically still within the allocated range, but because the diameter has changed in a big way, the entire tyre circumference has also been changed , rendering the speedometer inaccurate. More importantly, the increased wheel size may cause the wheel to hit the inner wheel wall of the vehicle when the wheel is turned to its fullest. In serious circumstances, it will cause uneven wear and tear for the tyre.
What the "Plus 1" and "Plus 2" mean in the picture below.

"Plus 1" means, if the tyre's thickness is reduced from 70 to 60, the wheel size has to be larger by an inch, to ensure the wheel circumference is the same.