What should I consider in finding the right tire sizes for my car?

Aside from physical and actual tire measurements like diameter and width, there are other factors that you have to consider in finding the right tires size for your car. These factors are the following:

  • load index
  • speed rating

Shop Tires By Size

How can I determine the tire size fit for my car?

Tires are being categorized by size using a 3-number code. In the series 225/55/16, for example, 2555 is the width of the tires, tire’s aspect ratio is 55, and it has an inner diameter of 16. 

Image source: kwik-fit.com  

The external diameter of the wheel is measured by the distance of one sidewall to the other. To get the wheel’s aspect ratio and the external diameter, along with the rim size, you have to drop an inch in the external diameter.

To get the external diameter, you must multiply by 2 the wheel’s aspect ratio, including the bottom and top sidewalls, and adding to it the inner diameter of the car. Once done, convert millimeters to inches. In this case, you will get 25.7 inches as the standard height. After getting the external diameter of the old wheel, match it with the new and replacement wheel. That’s the right tire size.

What Other Tires Fit My Car

If you’re thinking of shopping for a new car, you may have noticed that newer models have larger wheels and bigger tire sizes. Aside from the sleeker and cooler look that a bigger tire gives your car, it does provide for safer ride, particularly if you live in a flood-prone area or on an off-beaten path not yet reached by paved roads.

The sidewall is that part of the wheel which is located in between the inside and the outside diameter. The inside diameter is the area where the wheel meets the tire, while the outside diameter is the part where the pavement meets the tire.

If you have more sidewall, you also have more cushion. Cars which have 20, 19, and 18-inch wheels have very narrow sidewalls. These kinds of cars have improved handling but deliver a rather uncomfortable riding experience.  On the other hand, if tires have taller sidewalls, handling is adversely affected because there is more chance of unwanted lean and roll. It’s like hiking on a nice pair of hiking boots versus hiking in stilettos.

Fortunately, there is a middle ground between comfortable riding experience and good car performance, and it all goes down to the car’s tire size.

Whether you only want to soften the setup of your car or you are shopping for a lesser aggressive ride, remember that tire sizes matter.  

Stay Away from Cars That Require Increase in Wheel Size

There are many cars which offer different trim leaves. Those models which have the smallest wheel/tire combo are usually the base models. Top of the line rims are often seen with increased wheel size. More often than not, sport package options will increase the suspension’s stiffness while increasing the tire size. If you are not a car aficionado, you might be more contented with the stock setup.

For the most part, the driver, along with the passengers, won’t notice much difference if he has been driving stock all his life. And there’s nothing wrong with that. However, once they try the feel and handle of a bigger tire, especially one that serves to enhance the performance of the car, they will want to change the rubber of their other vehicles, as well.

However, if you prefer trims with bigger wheels but is not satisfied with the quality of the riding experience, you can just ask your car dealer to replace and mount different wheels to the car. Your car dealer knows which will fit or which won’t. You have to remember however that the Original Equipment Manufacturer (OEM) tires are pricier than the aftermarket counterparts.

Sport Tires versus Touring Tires

Tires come in different specifications, use, and sizes. Performance tires, aimed to improve traction, are usually made with softer compounds. The downside, however, is that the improved traction also paved way for the increase in road noise and a reduction in the tire’s life.

Touring tires, on the other hand, are made for usual driving on open roads and highways at a speed not greater than 70 to 80 miles per hour. These types of tires are usually softened but last longer than sport tires. Also, it helps improve the car’s overall fuel economy.

Minus One versus Plus One

If you already have a car and you want to improve its riding comfort, you can shop for aftermarket tire and wheel packages to help you achieve this purpose. If you now want to change the car’s original base wheels, you must remember that you can either go up or go down by an inch when choosing the replacement tires.

For instance, you have 17-inch wheels and you want to improve its handling, you can go higher by an inch and change it to 18-inch wheels. If you want to improve its riding comfort, however, you can down an inch and replace it with 16-inch wheels.

It is not ideal for you to go higher or lower than an inch because the suspension and springs of the cars are designed based on the original tire setup. If you would really push for a more radical change in tire sizes, your car might experience handling problems and at worst, suspension damage.

Also, the rotos and brake calipers of the cars are designed with minimal clearance between the wheel and the components. Should you really insist on moving more than an inch higher or lower, the wheels might not work properly as it would no longer fit over the brakes.

Where can I get help if I want to change my car’s wheel size?

If you want to increase or lower your car’s wheel size, there are many online resources and brick and mortar companies which can help you. These resources and companies have excellent tire and wheel fitting tools which would allow you to see how your cars will look with the tires you chose to mount and change.

The best tire manufacturers will also calibrate your speedometer to fit the bigger size tires. When you change the wheels of your car for more than a two-inch difference, the distance will be skewed. That’s because bigger wheels covers more ground in one revolution. You may think that you are only traveling 80 miles per hour based on your speedometer but you are actually at a 90-mile-per-hour speeds!

Performance and Safety

Mounting the right wheel and tire sizes and type is very crucial to your vehicle’s safety and overall performance.

The tires you choose for your vehicles should reflect your preferences and overall driving conditions like handling and vehicle responses. Thus, it is very important that you understand what size of tires is the best fit for your vehicles.

Determining the right tire size

Determining the correct tire size of your car is something you can figure easily on your own. All information you have to know is written in your car’s owner’s manual. If you already have this information and you want to replace your tires, you can just go over your tire manufacturer’s tire catalog.

Aside from physical and actual tire measurements like diameter and width, there are other factors that you have to consider in finding the right tires size for your car. These factors are the following:

  • load index
  • speed rating

If you don’t have your manual, you can also find a tire fit guide in the following:

  • driver’s side door jamb
  • Inside the car’s glove box door
  • On the car’s gas tank hatch

Let’s say that the tires are of proper sizes, you can also find details of the tire size on your current tire’s sidewalls. Then again, wherever you locate your tire size information, you will still need to decipher a number and letter sequence.

How do you read tire sizes?

Image source: fixaflat.com

Let’s take this number and letter sequence as an example: P225/70R16 91S

In most cars, you will see “P” at the start of the series of numbers. This is actually short for “P-metric.” A P-metric designation is a designation assigned by the Tire and Rim Association to all passenger car tires. This further means that the said tires are designed to be used only on passenger vehicles which include the following:

  • Cars
  • Minivans
  • SUV’s
  • Other light duty pickup trucks

If there is an “LT” label instead of “P,” it means that you need light truck tires. “LT” means LT metric, again a label designated by the Tire and Rim Association for light truck tires. Additionally, light truck tires are used on vehicles which are capable of the following:

  • Pulling trailers
  • Carrying heavy cargo

Lastly, “T” stands for “temporary” and is designated for spare tires, while “ST” means “special trailer.”

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After the letter, you will now see a series of numbers and these speaks of the correct width (millimeters) of the tires right for your vehicle.

Going back to the example P225/70R16 91S, the thickness or width of the tires always refer to the distance between the sidewalls. So, if the tire’s measurement is “P225,” it means it is for a passenger vehicle and with a nominal thickness of 225 millimeters.

Tire’s Profile and Aspect Ratio

After the label P225 and the slash mark, you will see another series of numbers which correspond to the tire’s aspect ratio. These numbers tell you how tall your tire’s profile is.

These numbers are delivered in percentages and usually, tire manufacturers compute these by dividing the tire’s tallness (off the rim) by its thickness. If the tire’s aspect ratio is 60, this only means that the tire’s height is 60% of its width.

The number 60, a lower aspect ratio for tires, generally offers better handling performance compared to those with higher aspect ratio.

Tire Stability and Construction

After the slash mark and the aspect ratio, you now see a combination of letters and numbers. The letter actually marks the kind of internal construction responsible for the stability of your car.

The two types of constructions that you can see on the tire’s sidewall are the following:

  • R which stands for Radial
  • D which stands for Diagonal or Bias Ply

The R type construction represents the majority of the wheels used in the US today. This is usually shown in the wheel size designation. R type means that the tire’s internal ply cords are radially oriented and are perpendicular to the rotation axis.

Diameter Code

After the tire construction type, we now see the tire’s diameter code. These codes are expressed in inches. In the example, we have P225/70R16 91S which means that the tire would fit a rim which is 16-inches in diameter.

Tire’s Load Index

These figure in the sequence actually refers to how much weight, in pounds, the tire can carry when inflated fully.

This is called load index because it does not specify, in exact and precise terms, the weight it can hold. If the number starts with 1 and ends in 150, this means the tire has a carrying capacity of 99 to 7,385 pounds.

Tire’s Speed Rating

The last and final number in the sequence speaks of the tire’s speed rating. Similar to the load index, the tire’s speed rating letter also refers to the tire’s specific capacity, measured and based on a standardized lab examination.

If, for instance, the tire’s speed rating is “S,” this means it is rated for up to 112mph. An “R” rated car tire means it is rated for up to 106 mph. These ratings are not recommended and are not suitable as cruising speed.

Benefits of Having larger tires

Image source: stancespice.com


    Improved hold

  • Shorter slowing distances
  • Faster car response times
  • Improved cornering stability

Disadvantages of large tires

  • More expensive tires
  • Higher oil use and consumption
  • Mediocre water draining capacity
  • Low aquaplaning resistance

Benefits of having thin tires

  • Improved resistance to aquaplaning
  • Better driving and riding comfort
  • Lesser tire noise
  • Less costly tires
  • Better driving experience in winter conditions

Disadvantages of thin tires

  • Reduced hold
  • Mediocre coping capacity on slopes
  • Longer braking distance

At the end of the day, the best thing to do is to seek professional advice to help you with your tire replacement needs.

Some people opt to do things their way, notwithstanding the fact that they are not very knowledgeable in what they’re doing. Experimenting is good but not with expensive things, like your cars.

In as much as you want to save on the cost, you cannot just replace years of skills and expert knowledge with gut feel.

The result of foregoing expert advice and service is sometimes costly. Instead of saving you end up harming the vehicle than “curing” it. You may have to pay for expensive repairs, or worst, you just might need to buy another car.

You can stop wondering, “What other tires will fit my car?” Save yourself the headache and call an expert today.  Just bring your vehicle over and let United Tires do the rest.