Wheel and Tire Plus Sizing: Learn How Plus Sizing Affects Your Car
New tires are most often purchased in the autumn or winter when good tread is important for driving in the adverse weather conditions. When it comes time to buy a new set of tires, knowing a little bit about these important car parts can really pay off.
A car’s manufacturer always stipulates the correct size of tires for that specific vehicle. This information is printed in the owner’s manual and can be found on the sidewall of the tire itself. In fact, the sidewall is an excellent communication source about the tire.
For example, a tire that reads “225/50R16” on the sidewall gives a lot of important details about that tire, including:
- The tire width of 225
- The sidewall height of 50
- The tire diameter of 16
- The tire type as radial (R)
These specifications have been thoroughly explained and can be further explored in our tire guide. Choosing the right tire size can affect the vehicle’s overall performance, so understanding all of the specifications is very important.
Tire Size Matters
The current trend is to have low-profile tires with large diameters. Not only do these tires look better than smaller wheels, but they also improve a car’s performance.
As the wheel size gets larger, a tire’s diameter must become smaller, causing the sidewall to lower as well. Despite these size changes, the overall diameter of the tire remains the same.
If the original equipment (O.E.) size increases by an inch, for example, the tire is converted to a Plus One size. This pattern is the same for all size increases. An O.E. increase of two inches causes a Plus Two size, and so on.
Plus size tires became a trend during the 1970s when Plus One and Plus Two tires were manufactured for many different vehicles. This meant that many car owners upgraded their standard 13-, 14- or 15-inch tires to 14-, 15- or 16-inch ones. Today, many tires are O.E. at 15 or 16 inches already, causing the plus size tires to be bigger than ever.
The increased width of plus size tires means that they also have a larger footprint from more contact with the ground surface. In addition, the shorter sidewall causes a lower aspect ratio. This pair of changes makes the lateral stability better and the steering more responsive in these vehicles, leading to a better performance overall.
Reasons for Plus Sizing
Lowering the vehicle profile and balancing the car’s shape with the wheel size simply looks better to most people. Because of this more appealing style, many vehicle owners prefer larger wheels on their cars.
However, the visual appeal is not the only benefit to plus size tires. The profile change also leads to several performance improvements, including:
- Better steering
- More responsiveness
- Greater comfort in the ride
- Tighter cornering
- Better grip
Each of these improvements is another incentive for drivers to plus size their tires. However, these advances are only possible if the plus sizing is done correctly for that particular vehicle.
Reasons Against Plus Sizing
In contrast to the improved appearance and driving performance, there are some aspects of performance that suffer from the larger tires and the lower profile.
The overall fuel economy of a vehicle with plus size tires will suffer. The larger wheels require bigger tires, and these are heavier than the recommended tires for the vehicle.
When the weight of the car has increased, it burns more fuel to move, reducing the fuel economy.
Likewise, the heavier tires and vehicle is more difficult to stop. This means that longer stopping distances are necessary in order to completely halt the vehicle. Drivers will need to use the brakes longer and possibly harder in order to get the heavier vehicle completely stopped. This could cause more wear on the brakes, brake pads and the suspension of the vehicle.
When vehicles with plus size tires meet potholes, curbs and uneven roads, the lower profile and the larger tires put them at a higher risk for tire and undercarriage danger. The shorter sidewalls of the tires are simply unable to withstand the impact when the road is damaged and uneven. Larger sidewalls would have been able to handle such issues. Potholes and curbs can also damage the side panels and the undercarriage of a low-riding vehicle, requiring more costly repairs than the vehicle would have seen if it were sitting higher. This is why cars with plus size tires should be wary of roadway obstacles and focus on avoiding them as much as possible.
When Tires are Too Big
When thinking about plus size tires and facing the decision about whether to choose them or not, many drivers wonder how big they can go without causing too many issues with their vehicles.
The answer to “how big is too big?” really depends on the specific vehicle and its performance. For example, putting wheels that are too big for the car’s engine on it will drastically reduce acceleration.
Maintaining the overall diameter of the wheel is the key to making plus sized tires a good choice. Larger wheels need lower profile tires in order to keep the vehicle working at its highest capacity.
More wheel, as with plus size tires, must equal less tire overall. When this rule of maintaining the proper diameter is disregarded, many issues can occur with the vehicle. For example, the speedometer and the odometer readings will not be accurate because the wheel cannot track the speed and distance.
Concluding Thoughts: Measuring the Pros and Cons
Adding plus size tires to a vehicle can have many advantages, most obviously including the improved appearance and performance of the car. However, as with any big change, there are negative consequences of changing the tire size indicated by the manufacturer that should not be ignored.
Drivers who are concerned about the safety and performance of their vehicles with plus size tires should always consult with professionals before making the tire change. These experienced individuals have all the information, and will take all the factors into consideration that you might miss on your own (for example: the particular car and the driver’s goals).