Getting new tires for your F150 is like picking out a new pair of shoes. You want to make an impression, but you also want them to fit right! Sure, you could always pay someone to pick them out for you and put on a perfect fit, but by customizing your F150 and choosing the biggest and best tires you can is part of the fun.
F150 tires: how big can you go? There are certain body types of the F150 that will allow you to put bigger size tires than average. To understand how big your tires can be you will need to know the rim size. Alternatively, you can lift your F150 to get even bigger tires fitted. However, something like a Super Duty can usually fit bigger tires without having to be modified or lifted.
Before you go out and choose the next set of big tires that will go on your F150, make sure you read through this article to get some information about sizing tires, fitting them, and how big you can go!
What are the standard F150 tire sizes?
To understand how tires fit onto the rim of your F150 and how big you can go, you first have to learn about reading tire sizes correctly. You can read the size of a tire easily from the raised numbering and lettering on the side of the tire.
The next section will teach you what each part of the tire code is and how to use it to determine if the tire will be a good fit or not your F150 – will the tires be too big…!
The sizes of tires have different terms that are important to be able to read if you are going to choose tires to fit your F150. Let’s look at an example of tire size and break down the different parts of the sizing.
Example tire size: 245 – 70 – 17 (Or 245 – 70 R17)
There are three sets of numbers on the sidewall of a tire that tell you the sizing of the tire and how it will fit onto a rim.
The first number in this example, 245, is the number that tells you the width of the tire from sidewall to sidewall in millimeters. To convert this measurement in millimeters to inches, you can divide the amount by 25.4. So, 245 / 25.4 = 9.64 inches.
Next, is the second number on the line of three numbers on the tire. This second number gives you the tires profile or “aspect ratio.” If you multiply the width of the tire (245) by the aspect ratio percentage (.70), you should get the height of one sidewall. So, 245 x 0.70 = 171.5mm or 7 inches.
The third and final number on the tire is the size of the rim that the tire will fit on. The diameter of the rim in inches will tell you if the stock rim you already have on your truck will fit this specific tire, or if you need new rims to go along with your new tires.
If you want to calculate the whole diameter of the tire, you must keep in mind that you will need to multiply the sidewall height by two and then add the width of the wheel.
One last thing that I want you to keep in mind is that when making these calculations, you are basing the numbers on the intended sizes from the manufacturer.
The actual sizes in real-life might be slightly different. The tire manufacturers’ dimensions should be followed closely instead of relying too heavily on your calculations.
Other F150 tire size considerations
Tire sizes are longer number lines. An example of a complete number line from a 2018 Ford F150 is LT245 / 70R17 / E 119S. Let’s unpack each set of numbers and letters because they each tell us something about this tire.
LT Intended Use
The beginning letters on the tire indicate how to use the tire. LT is for light trucks. You may also see P for passenger vehicles and C for commercial vehicles.
245 Tire Width
The number 245 tells us the width of the tire in millimeters. Remember, you can convert millimeters to inches by dividing this number by 24.5.
70 Aspect Ratio or Tire Profile
You read this number as a percentage or an aspect ratio on this tire of 70 percent. The aspect ratio is 70 percent, which means the sidewall takes up 70 percent of the tire. You measure the width from the edge of the rim to the side of the tire’s tread.
R Tires Construction
The letter here tells what the tire’s construction was. R means the standard building called Radial. Radial makes up 99 percent of constructed tires today. Other letters that you may see on tires for development are B for “bias belt construction” and D for “diagonal structure.”
17 Rim Diameter
The number 17 tells you the size of the rim that this tire can fit on. It will also let you know if you need to buy new rims for your new tires, or you can check the stock size and see if they will work.
E Load Range
This letter E lets you know the tires load range. An E is a load range of 10. As letters get further in the alphabet, the tire has a higher load range and can take more pressure. In other words, if the letter here is more rooted in the alphabet, the tire can carry heavier loads. Therefore, the tires with a letter later in the alphabet are stronger.
119 Carrying Weight
This number gives you the exact weight that the tire can handle. In this case, 119 means the tires are capable of carrying a load weight of up to 2992 pounds, or less. Higher numbers than 119 can carry a more massive load, and lower numbers can carry lighter loads.
S Speed Rating
The S tells you the maximum speed that the tire can safely withstand for up to 10 minutes. The S means that the maximum speed for this tire is 110 MPH for up to ten minutes of travel. Any rate or duration longer than this is unsafe use for this tire.
How big of a tire can you put on an F150?
It is essential to know the size of the rims on your F150 before you choose the size of the tires. If the rims are stock, you can probably fit 33 x 12-inch tires on a 4wd and 33 x 12.5-inch on a 2wd. Super Duty and lifted trucks can fit maybe two inches larger tires.
There are a few important spacing issues to keep in mind when you are shopping for the new tires that will be going to be big enough to fit your Ford F150.
Backspacing on new tires
Backspacing is measuring the distance that is between the hub mounting to the inside of the tire. If you add more backspacing, you are putting the tire more to the center of the truck.
If you have a backspacing at 0, for example, that means that you have perfectly lined up hub mounting with the centerline of the rim.
In other words, the backspacing equals 1/2 of the rim width. On the opposite side, more backspacing means that the tire will sit outside of the wheel flange and away from the hub mounting surface. More backspacing also may increase the chances of the tire rubbing up against the back fender.
How do you measure the backspace on a Ford F150?
To measure the backspacing of your tires, you will need some tools and to follow a few steps (source).
The tools you will need are:
- A tape measure in order to measure the wheel space.
- A straight edge.
- A wheel without the tire.
Step #1: Lay wheel down
Lay the wheel down so that the backside of the wheel is facing you.
Step #2: Straight edge
Take the straight edge and lay it across the flange of the wheel diagonally.
Step #3: Measure
Use the tape measure to get the length from where the straight edge touches the flange to the hub mounting pad of the wheel. This measurement is your backspace measurement. Take a tape measure and measure the distance from where the straight edge contacts the inboard flange to the hub mounting pad of the wheel.
What is offset on tires
You should also consider the measurement of offset. Offset is either the negative, positive, or zero position of the centerline of the tire concerning the hub mounting surface. Offset is measured in millimeters and can show in three ways. Offsetting does one of a few things.
Most importantly, if your wheels have incorrect offsetting, it can negatively affect the handling of your F150. It is best to keep the tire at zero offset. Now, let’s look at each type of offset so that you can accurately diagnose any handling problems with your new tires.
Negative tire offset
The negative offset of the tire is when the hub-mounting surface is positioned in the back towards the brake of the wheel. If the offset is negative and not positioned correctly, this could affect the handling of the F150 severely.
Positive tire offset
A positive offset is when you can visually see that the hub surface is sitting towards the front of the wheel. Most wheels are going to have a positive offset.
Zero offsets of the tires is what it sounds like; there is no difference between the space of the hub on either the front or back of the wheel. You will have the hub directly over the centerline of the tire at a zero offset.
Offset is an integral part of understanding whether or not your truck tire will fit on your F150. Luckily, there is an online conversion calculator that can help you to know if your tires will fit on your truck. The conversion calculator for offset will also help you to calculate the offset of your tires with your truck hub-mounting surface.
The tool only works if your truck is stock. It is faster and easier than measuring yourself, but not as precise. So, if the offsetting is tight and you need to be exact, measure the offset yourself.
How to put big tires on an F150 that don’t fit
So, you measured and calculated and finally found the perfect set of big tires for your F150 and are ready to install them, but then they don’t fit.
Don’t worry! It’s okay because there is always a way to make it work on a Ford!
There are several options to make them fit on a set of tires work for your F150. Don’t return your new tires just yet. Here are some of your options.
These options include wheel spacers and fender rolling, among others. Be sure to invest time in re-measuring the tires to make sure that they don’t fit before investing more money in additional fixes to make the tires work. You don’t want to spend extra time and money, installing your new tires if you don’t have to.
Wheel spacers work like a wonder to make tires that may be too big to fit perfectly on your truck. They are metal spacers that fit in between the wheel and the hub. The spacers force the wheels outside of the profile of the truck and give them clearance.
Spacers are excellent for stopping rubbing by creating clearance. The only downside is that spacers can change the actual weight misdistribution and geometry of the body of the truck and cause undue stress on the entire system of the F150.
Fender rolling is a lot like wheel spacers because it can help to eliminate tires rubbing against the hub. Fender rolling is an actual modification to the fender, so we suggest getting professional help from a body shop.
And as always, do your research on the shop before you go trusting them with the modifications on your truck.
Also, since there is a danger of damage to the fender or paint job of the truck, it is suggested to use the tools of the body shop and seek professional help when attempting to do fender rolling. The primary action of fender rolling is to bend the lip of each fender from an “L” shape into an angled “V” shape. This should help to allow the larger tire fit in the hub without rubbing on the fender.
How do big tires change an F150?
Big tires will have you sitting up higher on the road and may allow you to get a bit wilder when you want to go off-roading on the 4×4 terrain. However, there are some other things that larger tires will change about the whole system of your truck that you should be aware of.
For example, since the calibration of the speedometer and odometer are for smaller stock tires, the readings will be incorrect. There are ways to fix both of these tools after you upgrade to bigger tires on your truck.
You can recalibrate both of these tools at your local mechanic’s shop for a small fee. Or, you can just do a bit of mental math as you drive to know how far and fast you are going.
Also, since you have changed the tires to larger tires when you sell your F150, you should disclose this information.
Disclosing the information on installing larger tires is especially important if you do not recalibrate the speedometer or odometer.
Remember, the readings will still be off. You don’t want anyone to get caught for speeding because they didn’t know the speedometer was off!
The tires on an F150 can go very big. There are even ways to make tires that don’t seem like they are going to fit work for your truck.
Now you know how big F150 tires can go, when installing the new tires, keep in mind that the tools for reading speed and distance in your F150 are going to change. You should recalibrate these tools after installing large tires.
When looking for a new tire, take the stock rim size of your truck into consideration. Also, the profile of the tire itself is crucial. Reading the tire coding gives you all of the information that you need to make informed decisions about installing tires that will fit perfectly for your F150.
I suggest looking at both the Ford schematics and using calculations. Using the calculations and schematics help to double-check that your next set of big tires will fit perfectly.
Also, the offset and backspacing are visual clues that can let you know if something is off and can also be calculated even before you install the tires. Calculating before installing new tires is the best option, as you will know before going through the trouble of putting them on, only to realize that you need wheel spacers.
Enjoy your tires and go big on your F150, you never know when you might need to downgrade!