Tire Definition & Tread Guide at Lexus of Royal Oak
They’re on every vehicle you see, but you may not realize all that goes into tire sizes and ensuring that they’re perfect for the model they’re fitted on. Your Lexus was no different, from design to build it was intended to have a specific tire size that improves everything from performance to fuel efficiency to safety. That’s why we here at Lexus of Royal Oak recommend you get the original manufacturer tire size for your vehicle, from selecting winter tires to performance variants. Read on to learn in-depth how to read the numbers and lettering on your tires, as well as understanding the purpose of each groove, slot and rib in your tire treads! Find the perfect-fitted tires for your vehicle in our online tire store, or contact our dealership for more.
Tire Size Definition Glossary
If you’ve ever looked closely at a tire you’ve probably seen a collection of numbers and letters printed along its side. You can be forgiven if you don’t understand what they all mean, that’s why we’re here at Lexus of Royal Oak to help you learn everything you need to about tire sizes and their markings. Let’s use P235/40R19 99V as an example and break it down for what each segment means:
P
This capital P letter indicates a Passenger tire in a P-metric size. Tires without this P can be made for passenger vehicles, but are European metric sizes with different load or speed ratings.
235
This is the tire’s width, measured in millimetres and from sidewall to sidewall. This information helps let us know the width of the rim that’s able to be used to mount the tire on.
40
This is the aspect ratio of the tire, as a percentage of the width. Thus, with this example tire it would be 94 mm (235 x40%). High performance tires have a lower aspect ratio, below 55% as lower ratios equal better stability
R
This is the radial construction, meaning the strengthening and reinforcing plies radiate on a 90° angle. Bias-ply tires have a 60% angle degree in comparison, and thus deliver not as good fuel efficiency
19
This represents the diameter of the wheel this tire can be mounted on, in inches. It doesn’t matter if it’s a steel or alloy wheel.
99
This is the load index, outlining its load-carrying capacity, and how much weight it’s able to support at its max air pressure. In this case our 99 load index equals 775 kg. On cars and light trucks these load indexes range from anywhere around 80 - 110 (450 - 1,060 kg).
V
This is the speed rating indicator. Where the speed capability of the tires matches the top speed capability of the vehicle they’re on. Each letter corresponds to a max speed rating. For example, on Lexus vehicles, S = 180 km/h, T = 190 km/h, H = 210 km/h, V = 240 km/h.
Tire Tread & Sipe Patterns Explained
A tire tread is more than just random squiggles and lines, all of those designs mean something, and especially when you’re dealing with the kinds of weather we see here in Calgary. Tire treads let you know how equipped they are to perform in conditions like wet roads, snow, highways and more.
1. Sipes
These are all of those little “cuts” or slots you see molded into the tire. A lot of sipes mean better performance in wet traction. A solid block style equals better tear resistance when driving over gravel.
2. Lateral grooves
These are the slots that go across the tire. Open grooves mean better performance on snow, mud and sand. Closed grooves means a more quiet ride and higher cornering performance on highway roads.
3. Shoulder blocks
The “shoulder” refers to the side of the tire that wraps along the sidewall. Open shoulder blocks equal better traction. Closed shoulder blocks equal a more quiet ride and higher cornering on highway roads.
4. Centre rib
This is the main strip of rubber in the middle of the tire. A solid centre rib provides better highway handling. No ribs but with lugs instead delivers higher traction.
5. Circumferential grooves
These are the deepest and most significant grooves molded in a tire. Wide & clear: helps to improve the dispersion of water at top highway speeds. Zigzag & lugs: improves traction in the snow or off-road.
Tire DOT Marking Meaning
Every tire that is manufactured gets an identification number, either called a Tire Identification Number (TIN) or a Department of Transportation (DOT) number. These numbers are printed on the sidewall of the tire, around its bead area where it would be fitted onto a rim. It’s usually only found on one side, and could face either inward or outward. These numbers help to track the tire, and must be recorded to properly register your tires, as well as signifying that they’ve met top safety standards.
Book an Appointment
If you have any questions at all about tire sizes, their treads, deciphering their numbers and letters, terms or anything else, please don’t hesitate to contact our Lexus tire experts here at Lexus of Royal Oak. Even if you just need help shopping for a new set on your vehicle, be it winter, summer or performance, or need an installation, changeover or wheel alignment, we’re always here to assist.