Breaking Down Tire Size
If you have ever purchased a tire, you will know that they come with complex numbers on the sidewall. For most of us, the numbers are nothing short of gibberish. But they are essential codes that give a lot of information regarding the tire.
Tires sizes are measured in a mix of millimeters and inches. Let's break the tire code. To make this easier to understand, we will use the code P 215/65R16 89H
Starting from the left, you will find a few letters like P, LT, or ST. These codes stand for the vehicle the tire is to be used on:
- P means the tire is suitable for a Passenger Vehicle
- LT means the tire can be used on a Light Truck
- ST means that the tire can only be mounted on to a (Special) Trailer
The three-digit number displays the tire's width in mm, measured from one side to the other while looking at the tire from the front or back of the vehicle. 215 means that the tire is 215 mm wide.
Right after the forward-slash is a two-digit number, which signifies the tire's profile. This represents the height of the sidewall of the tire as a percentage. For 215/65, the sidewall height is 65% of 215, which is 139.75 mm or 5.5 inches.
The letter after the aspect ratio depicts the construction style of the tire
- R means the tire is Radial
- D means diagonal or biased tire
The next number is the size of the wheel or rim in inches. For our example, the tire is made for a rim size of 16 inches
The next number, which can be two or three-digit, signifies the load index; how much weight the tire can support. For our example, 89 means that one tire can support a max load of 1279 pounds.
This letter signifies the tire speed rating, which is the safest speed at which the tire can travel for a significant time period. The vehicle's maximum speed is usually kept below the tire's speed rating.
How to Change Tire Size
It is possible to change the tire size on any vehicle, but there are several factors to consider before that.
- The new tire should be within your vehicle's tolerance level. Putting in too large a tire can cause it to rub against other parts, leading to damaging the vehicle and the tire
- Your vehicle's speedometer is calibrated with the OEM tire size. Changing the size will give an erroneous reading. It is best to consult a tire expert to know how much difference you will have
- Wrong tire sizes can affect the handling and stability of your vehicle. Try to stay closer to the OEM recommendations
205 Tire vs. 215 Tire
With the information we have now, we know that the main difference between a 205 tire and a 215 tire is in width, which is 10 mm more on the 215.
Given that we had to replace a 205 tire with a 215 tire, we would need to make some calculations so that the diameter of the wheel (rim + tire) remains the same.
IF there is any change in the diameter of the wheel, the speedometer will not give the correct reading, and it will also affect the ground clearance of the vehicle.
The tire will have a larger contact patch with the surface it runs on with the increased width. This has both benefits and downsides.
The benefit, in this case, will be an improved road grip and traction as the larger contact patch will mean more friction between the tire and the surface. You will feel your vehicle corner better and with less tire squeal. You will also notice less wheel spin with one of those powerful launches.
There is also an added benefit of better handling at higher speeds, and you will be able to maneuver the vehicle with more confidence.
The downsides, firstly, due to the added friction, the vehicle's fuel consumption will increase. This happens because the drag on the vehicle increases, and the engine requires more power to overcome the drag.
Another downside is a slightly heavier steering wheel. The steering wheel will be harder to turn,especially when the vehicle is stopped at slow speeds. You might get used to the difference quickly, especially with the modern electronic steering systems.
On the other hand, if your vehicle comes with a 215 standard, and you are trying to swap in a 205, the effects will more or less be reversed.
With a smaller contact patch, you will notice a slight improvement in fuel economy and find the steering a little easier to move around.
Your vehicle's handling and cornering abilities will be slightly reduced, and you may not feel as confident when maneuvering your vehicle at high speeds.
Before swapping in the wider tire, it is important to check the adaptability of your vehicle. If you drive a car with no extra room in the wheel wells, you might end up having tires that rub against the mud shields, suspension parts, or the inside of the wheel wells.
One last benefit of the wider tire is that most car enthusiasts like the looks of a broader tire on their vehicle. Some go far to make modifications to their vehicle to install wider tires, to get that sporty look for their vehicle.
About The Author
I've spent many years selling cars, working with auto detailers, mechanics, dealership service teams, quoting and researching car insurance, modding my own cars, and much more.Read More About Charles Redding