If you are considering upgrading your vehicle's tires to a bigger size, there are some things you need to know before making the change. We have compiled a list of considerations so that you can make an informed decision before changing your tire size.
Changing the tire size of your vehicle may have unintended consequences. Both speedometer and odometer readings can be altered when a vehicle's tire size is changed from the factory specifications.
If you want to learn more about how and why the speedometer and odometer readings are altered when tire size is changed, keep reading. We will look at other things that can occur while changing tire size and ways to change tire size with little to no effect.
What Happens When I Change Tire Size?
Some of a vehicle's systems, like the speedometer and odometer, are based on the rotation cycle of the tire. When the tire's overall diameter size is altered, the calculations are no longer accurate until a system recalibration occurs.
However, there are some size changes you can make without affecting the systems, but it requires some mathematical calculations to figure out which sizes don't affect the overall diameter. There are tire size calculators available to help you figure it out.
The speedometer calculates a vehicle's speed by monitoring how quickly the tires complete a rotation cycle. The system's calculations rely on the data from the tire's specifications.
When this changes, the miles per hour are no longer accurate because the tire's rotation size has changed. An inaccurate reading could cause you to get an unwanted speeding ticket.
The odometer uses a tire sensor to keep track of each time the tires make a complete 360-degree turn. Using that information, it calculates mileage.
The internal mechanisms are calibrated to the manufacturer's tire size specifications. A bigger tire takes longer to complete a rotation and covers a longer distance. Therefore, the mileage calculation is skewed unless you recalibrate the odometer to the new tire size.
What Is Meant By Bigger Tires?
Bigger tires are anything larger than the standard factory specifications. Adding bigger tires is often referred to as "plus sizing" when you increase the overall tire dimensions or "plus zero sizing" when you alter dimensions, but the overall calculation doesn't change.
How much bigger you can go depends on safety guidelines and the results you want to achieve.
When looking at tire size, it is important to know the basics of tire language and understand the meaning of each letter and number in the printed tire size. This information can help determine if you can add bigger tires, bigger wheels, or both.
The first number gives you the mounted tire's width at the widest point in millimeters. Example: 245 = 245 millimeters.
The second number gives you a ratio of the tire's sidewall height to the tire's width. Example: 60 means the sidewall height equals 60% of the tire's width.
The third number indicates the inner diameter or the size rim the tire fits. Example: 16 means that the tire fits a 16" wheel.
Bigger can refer to a larger width, a larger diameter, or a larger percentage of the sidewall height to width. Each one can have different effects to consider.
It is also important to note that when you add bigger tires and/or wheels, you could be adding future expenses. Larger tires generally cost more and can be more challenging to find, often meaning special-order rather than standard stock at tire retailers.
If you have to change your wheels to accommodate the larger size, that is an additional expense to consider.
Why Add Bigger Tires?
There are a few reasons someone might decide to add bigger tires to their vehicle. Some are for the better overall performance of the vehicle, while others are only for aesthetics.
One consideration is ground clearance, especially if you use your vehicle for off-road work or recreation. A larger tire will raise the vehicle, giving more room between obstacles on the ground and the vehicle's underside.
You don't want a large rock to puncture your oil pan or cause any damage to the vehicle's undercarriage.
Another factor is the clearance between the tire and the fender, known as the fender well gap. If the gap is large, you might not like the look. Switching to a taller tire can reduce the gap, improving the vehicle's appearance.
Traction And Stability
Bigger tires have more surface area that hugs the road, giving you better traction and braking ability. You also gain some overall stability with a bigger tire because of more equal weight distribution.
Larger tires may slow your initial acceleration when stopped but can help you achieve a higher top speed. You can also experience better cornering and handling at higher speeds with bigger tires for when you are feeling sporty.
Who doesn't want a good-looking ride? Larger tires can change the appearance of a vehicle, especially when paired with new wheels. While tires alone might not complete a makeover, it is usually part of the package. Larger tires often go together with a lift kit, especially on 4x4 vehicles.
Do Bigger Tires Affect Gas Mileage?
According to energy experts, up to 30% of your vehicle's fuel consumption is related to the tires. Generally, bigger tires decrease fuel efficiency because of the added weight and resistance. Still, on an individual trip basis, it really depends on the type of driving that you are doing.
Smaller tires take less effort to get started moving, especially in stop-and-go traffic, which means less strain on the vehicle's engine. If you do a lot of city driving, smaller tires rather than larger ones are the more fuel-efficient choice.
For uninterrupted high-speed driving, a larger tire works less to cover more distance, so they might actually be more efficient on long trips. However, the average driver will do more city driving, so the open road efficiency probably won't offset the efficiency lost in day-to-day driving situations.
Are Other Systems Affected By A Change In Tire Size?
In addition to the speedometer, odometer, and fuel mileage, other aspects of your vehicle's functions might be affected by a change in tire size. These effects might not occur in every instance but should still be considered.
Anti-Lock Brake Systems
ABS braking systems function by the rotation of the tires. We know that larger tires have a different rotation time than smaller ones. This can confuse yourABS, but most newer systems can recalibrate automatically, while the tire retailer can reprogram older systems during installation.
It is best to upgrade your brakes when adding bigger tires to accommodate the heavier weight. Adding bigger tires may not cause your brakes to fail, but it could impact the stopping time in an emergency situation. It is always better to be safe rather than sorry.
Vehicles with tires upgraded from factory specifications will handle differently, which has positive and negative effects. Wider tires can increase road grip, which is good but can decrease your turning radius. Tires sized too large change the center of gravity which can result in a rollover accident.
Bigger tires can limit the space your suspension needs to absorb any impact from rough roads adequately. In addition, the limited clearance space may even cause your suspension components to rub the inside of the fender resulting in damage. Bigger tires can lead to an overall rougher ride in your vehicle.
According to tire experts, you lose torque for every inch added to the height of your tires, and bigger tires require a larger torque requirement to complete the rotation. This situation can lead to problems in other mechanical systems.
We previously established that changing tire size affects torque. This effect carries on to the transmission because the torque loss causes the transmission to work harder when the gear ratios aren't adjusted to accommodate a different tire size.
An overworked transmission can produce too much heat, which can cause damage to some of the internal components.
That loss in torque can also negatively affect your vehicle's towing capacity. However, this might not make much difference unless you are hauling close to the the limits of your vehicle's towing capacity.
You may want to read the fine print in your owner's manual because adding bigger tires outside certain specifications can sometimes void your manufacturer's warranty.
Wrapping It Up
There are many reasons a car owner might upsize to a larger tire. There are even ways to change size with little effect. If done within safety guidelines, the benefits may outweigh the slight alterations to meter readings and fuel efficiency.
Read Do Bigger Tires Last Longer? for more information when adding bigger tires to your vehicle.
Consider reading Can You Put Wider Tires On Stock Rims? if you are thinking about adding wider tires but not changing rims.