What Is The Biggest Tire for a 18 inch Rim

When you decide to replace tires on your rims either due to some customization or replacement of the worn ones, after some time of searching you discover that there is a huge variety of tires for 18 inch rims.

The situation might be more confusing especially if you are performing tire change for the first time. Various numbers on the tire bead may bewilder you in finding the best option, so it is important to know what they mean to ease the process of selecting the set of tires you need for your vehicle.

So, what is the largest tire you can put on an 18-inch rim?

For a convenient car or tiny crossover it can be a 27-inch tire depending on your arch size. If you are driving a pickup truck or SUV you can fit even a 38-inch tire size.

The optimal variant of bigger tire for passenger vehicles with 18-inch rim has the following parameters – 225/65R18, for pickup truck or SUV – 325/65R18.

Bigger than stock tire size may require you to make some modifications to your vehicle like installation of wheel spacers, arch trimming or lift kit purchase – everything depends on the tire size you choose and vehicle type you have.

The List of Tire Sizes Recommended by Tire Manufacturers for 18-inch wheels

How Do You Read Your Tire Size?

Either you are looking for your tires online or visiting a tire shop only knowing that it has to be 27 or 38 is not enough. Even if you search for the exact tire parameters with the same configuration as you previously had, it may have differences in numbers. Additionally, every tire is intended for a certain type of the vehicle taking into account such notions as surface, weight load and speed rating.

Below we will consider how to decode the information on the tire.

As an example let`s use the following tire parameters: LT325/65R18.

A letter at the beginning refers to a vehicle type at which this tire can be mounted on. “LT” in our case stands for light truck type of the vehicle.

If you see letters P on the tire it shows that it can be used on passenger type vehicles, if ST – the tire is made for special trailers like boat, utility trailer or car that can handle heavy loads at the speed under 65 mph.

The second number which is 325 in our case refers to a tire width in millimeters.

The number that comes after slash 65 is a sidewall height. Sidewall height  is a distance from wheel rim to the top of the tread expressed in percentage, like 75% in our example.

The letter means tire type, in our case R stands for radial tire tread type. Tires also can contain letter D meaning that they have a diagonal tread pattern.

And the last number, which is 18, means the rim diameter in inches.

As you can see, reading tire size is simple when you know what relates to what. If you`re facing issues remembering numbers and letters, make a handy note for yourself, so you can easily use it while selecting the best bigger tires for your 18 inch rims.

What Is the Biggest Tire That Can be Put on a 18 inch Rim?

Now it’s time to discover what is the biggest tire that can accommodate your 18-inch rims.

For a convenient car or tiny crossover it can be a 27-inch tire depending on your arch size. If you are driving a pickup truck or SUV you can fit even a 38-inch tire size.

Passenger vehicles and tiny crossovers were created mostly for urban conditions. Their wheel wells and ground clearance are not big and there is no much necessity to mount large tires on such vehicles.

However, if you are wondering what can be the biggest tire size for a passenger vehicle here are the parameters: 225/65R18.

Most car enthusiasts mark that if you select these tire sizes, you can install them on your vehicle without any side modifications. If you are building a custom stance flush or hellaflush project, 225/65R18 is your option.

Such vehicles as pickup trucks and SUVs have enough arch space and ground clearance. The biggest tire option for them has these parameters: 325/65R18.

In the majority of the situations you need to additionally afford a lift kit, make minor arch trimming works and use wheel spacers, so the tire won’t rub your arches.

Bigger than stock tire size may require you to make some modifications to your vehicle like installation of wheel spacers, arch trimming or lift kit purchase – everything depends on the tire size you choose and vehicle type you have.

How do Bigger Tires Affect Your Vehicle?

Before switching to larger tires on your SUV or pickup truck, it is good to understand what advantages and disadvantages it may bring you.

Let’s consider the advantages first

Undoubtedly, mounting bigger tires is one of the accessible types of vehicle modification. Larger tires can make your vehicle look renewed and more muscular, additionally to an unusual outlook you obtain more ground clearance which you can use off road for passing through obstacles and climbing hills.

Additionally with bigger tires you get better grip with surface stability and while you are hitting small portoles, bumps, rocks or debris the vibration from the wheels to vehicle body and you is less noticeable. Your ride becomes more comfortable and enjoyable.

Now move on to the disadvantages of bigger tires

In most of the situations bigger tires require additional modifications to your vehicle, which of course may take more time and money for it.

It may occur that after getting desired bigger tires, they just won`t fit, so you have to consider some variants on how to fix it. It means that you may need a lift kit purchase, arch or fender trimming, wheel offset or backspacing change according to your case.

Bigger tires affect speedometer and odometer reading, anti-lock brake system and tire pressure sensors. It is important to align or calibrate them to correspond to the new tire size, which of course involves additional spendings.

If you noticed that your gas mileage decreased a bit, the thing might be in the bigger tires on your SUV or pickup truck. Larger tires weigh more, so the engine needs more effort and rpm to rotate them resulting in increased fuel consumption.

To Sum Up

Now you know, what is the biggest tire for an 18-inch rim: for a city vehicle or small crossover it’s a 225/65R18, and for big trucks and SUVs it’s 325/65R18.

The numbers may differ depending on your vehicle and how far you can go with the biggest tire for your 18-inch rim.