Getting new tires can be exciting for some people, but most of us do not find tire shopping to be exhilarating. We want you to feel confident when it comes time to buy tires, so this is a quick guide to how tire sizing works in terms of metric versus imperial sizing.
A 35-inch tire and a 315 tire are the exact same size tire. Essentially, it is an alternative way of describing a tire. The 315 is the millimeter measurement of the tread width, while the 35 inches is the width of the tire multiplied by the aspect ratio.
More specifically, the measurement 315/70/17 is the exact equivalent to a 35-inch standard tire.
Keep reading to learn how tire sizing works and what to look for when shopping.
Essential Elements for Choosing the Right Tire
We have laid out some essential elements that will help explore tire options and ratings.
The tire size brand on the sidewall of a tire features a series of numbers that give a lot of information. On a 35-inch tire, you will likely see a size brand that looks like this: P315/70/17.
You’ll notice that the number 35 is not anywhere in that code, but that is the commonly accepted metric label for a standard 35-inch tire.
Metric sizing refers to the metric system of meters, centimeters, millimeters, etc. This sizing system differs from the imperial or standard system, which measures inches and feet.
On a 35-inch tire, the number 315 refers to the width of the tire treads in millimeters, while the tire’s diameter in inches is 35. As you can see, the two numbers actually aren’t related at all.
Here’s everything you need to know to read metric sizing.
Vehicle Type – P/LT/M+S
The ‘P’ here refers to it being a passenger vehicle. Other common letters you may see include:
- LT (Light Truck)
- T (Temporary Spare)
- Unique models may sport an M+S mark (Mud and Snow)
The M+S mark indicates they are high performers during extreme weather conditions. If the M+S marking has a snowflake with a three-peak mountain alongside, it has exceptional snow capabilities, making it a winter tire model.
Width – 225
The width is in millimeters and refers to the tread width.
Aspect Ratio – 70
The aspect ratio is essentially the profile height of your tire. This ratio helps people determine what tires can fit on their car with suspension lifts.
Construction – R
Here, ‘R’ stands for radial, which refers to the inner construction of the tire. Most people don’t need this information to buy tires, as most are radial.
Rim Diameter – 16
This metric is the rim size in inches so you can determine if the tire will fit on your vehicle’s rims.
Load Index – 91
The tire load index is the total amount of weight that the tire can carry safely. However, the number, in this case, 91, is not in pounds or any other metric measurement.
Instead, the 91 on the tire correlates to a scale that indicates the maximum weight. For a load index of 91, the tire can safely carry a maximum of 1,356 pounds.
Thankfully, this metric isn’t necessary when choosing standard passenger vehicle tires.
Speed Rating – S
And lastly, the speed rating is what high-speeds the tire can withstand. ‘S’ means it can withstand speeds up to 112mph.
Shopping for 315 Tires
If you are thinking of choosing 315 tires for your vehicle, you must follow some essential guidelines. This way, you will be safe on the road and avoid causing any mechanical issues from the wrong size tire.
Not all makes and models of vehicles can support 315 tires, unfortunately. Before switching tire sizes or brands, check the owner’s manual or contact the manufacturer for details on your automobile’s capabilities for tires.
If this tire should not be on your vehicle, it could be for several reasons, including:
- Size too large
- Not ideal for some weather conditions
- Recalibration of the speedometer or odometer isn’t possible
Which Applications Are Best for 315 Tires?
Many drivers prefer the look and size of 35-inch tires. Consequently, it is possible to use these larger models on some vehicles, but they may require modifications to accommodate them safely.
As you can see from the tire size brand, a 35-inch or 315 tire has an aspect ratio of 70, which gives it a higher profile than standard tires.
If you are exploring the idea of 35-inch tires for your vehicle, you may have to:
- Install a lift kit on your truck or SUV to accommodate the larger tire
- Trim excess material around the wheel wells to prevent rubbing during turns
- Recalibrate the speedometer so the odometer measures correctly
- Accept that a 35-inch spare will not fit in the standard spot to carry along
- Realize that you will have higher fuel costs as a result
Typically, 35-inch tires will work well on larger vehicles, such as trucks and SUVs. Even so, some vehicle models will still require you to install a lift kit and other modifications to accommodate them.
These tires have stronger sidewalls that will perform well in rough terrains, such as off-roading, and are ideal for better towing and hauling capacity.
Here are some quick tips to help you navigate the mission of getting new tires.
Replace All Tires
If you have one tire ruined, you may feel tempted to replace just the one tire, but experts say it’s best to replace all four at once, even if the rest look fine.
It may seem like a waste to remove three perfect tires, but one new tire can pull your car in a different direction from the three worn tires, which can affect the sensors on traction control and antilock braking systems.
We know this isn’t always financially feasible, though, so it’s okay to replace two as a set if four new tires are out of the question.
Then, when your budget allows, you can replace the remaining two. Just be sure to do it within a couple of thousand miles of replacing the first two.
Set a Budget
As discussed above, tires ratings are for different weather, speeds, and purposes, and, of course, 35-inch tires will cost you more than factory standard models.
Try to set a budget between $750.00 and $1,200.00, depending on the quality and type of tire you want. Having a specific price point in mind helps narrow down the options, so it’s easier for you to decide.
Talk to an Expert
If you still have no idea what the ideal tire and size is for you and your vehicle, there are plenty of tire experts willing to help you figure it out.
Choose a reputable retailer with knowledgeable staff eager to help you find the right tires for your vehicle. Don’t be shy and ask for help if you need it.
Tire sizing isn’t rocket science, but it’s close. We hope this guide has clarified some of the most confusing aspects of choosing a tire and determining the correct size.
Nothing could be worse than buying the wrong tires. It’s inconvenient and costly, but it can also be dangerous when driving.