The best way to Learn Tire Sizes

Crouching beside your automobile and studying the jumble of numbers and letters on the facet of your tires might sound hopelessly complicated. However we’ll let you know learn how to crack the code so you may perceive what tire dimension numbers and letters imply. This will even allow you to match your automobile’s tire dimension to your driving necessities.

Discovering your tire dimension

If all you need to know is your tire dimension, the quickest method to get that data is by going to a web based retailer's web site akin to TireRack.com. Enter your automobile’s 12 months, make and mannequin, and the positioning will let you know what dimension tires suit your automobile. In case you’re merely changing your tires and you want the best way the automobile rides and handles, purchase the same-size tires that got here with the automobile.

However if you wish to perceive what the letters and quantity check with, and also you’re contemplating making changes to your tire alternative, learn on. It’s also possible to check out the tire dimension chart beneath, which summarizes the data.

What tire dimension numbers imply

All of the numbers check with measurements whereas the letters check with tire varieties and scores — as we’ll clarify later. Let’s deal with the numbers first. For example, we’ll take into account this tire dimension: P225/50R16 92Y.

Tire width

The primary group of numbers, 225, refers back to the width of the tire as measured in millimeters from one facet of the tire (the sidewall) to the opposite. Mainly, that is the width of the tire tread that’s touching the street. Wider tires present higher traction to keep away from skidding whereas cornering or braking.

Facet ratio

The second set of numbers after the slash, which is 50 on this case, is definitely a proportion, so it's 50%. It refers back to the peak of the tire (from the wheel to the tread) in contrast with the tire’s width. So, on this instance, the thickness of the tire is 50% of the width. The decrease this quantity, the thinner the tire is when considered from the facet. Tires with decrease facet ratios — known as “low-profile tires” — present higher dealing with.

Wheel dimension

The third group of numbers, on this case 16, refers back to the diameter of your wheel (or rim), measured in inches.

Load index

The final set of numbers, 92 in our instance, refers back to the load index of every tire. That is the quantity of weight that every tire helps. Nevertheless, to get the precise quantity in kilos, it’s important to check with a load index chart, which converts this quantity to the overall weight. On this case, every of the 4 tires can carry 1,389 kilos. When changing tires, be sure to meet or exceed the load index of the unique tire. The load index can also be listed on the placard within the driver’s door jamb.

What tire dimension letters imply

Now let’s transfer on to the letters which might be interspersed with the numbers and see what they inform us.

Service description

In our instance — P225/50R16 92Y — the letter “P” in entrance of the numbers means this tire is for passenger automobiles. Different designations may be “LT” for mild truck or “T” for a short lived (a spare tire). If there isn’t any letter earlier than the primary three numbers, it’s a "Euro-metric" tire that conforms to European requirements, which could have a distinct load index.

Tire development

Normally, there will likely be a letter "R" after the facet ratio, which tells us this can be a radial tire (constructed with the rubber strips operating radially). That is pointless as a result of nearly all passenger tires are radials. It’s a holdover from the previous, when most automobiles got here with bias-ply tires. Some vans nonetheless use bias-ply tires, and they’re marked with a “B.”

Velocity ranking

The ultimate letter, on this case “Y,” corresponds to the utmost pace at which the tire can safely journey for an prolonged time frame. “Y” is the very best ranking and it means the tire can deal with speeds of as much as 186 mph. “S” is the bottom pace ranking, which suggests the tire is protected for as much as 112 mph. “Z” was the very best ranking for speeds over 149 mph. However as tire expertise improved, “W” and “Y” had been added to match increased most speeds.

Tire dimension chart

Tire dimension element	What it’s	What it means
P	Service description	The kind of tire — normally “P,” which suggests it’s for a passenger automobile.
225	Tire width	The width in millimeters.
50	Facet ratio	The ratio, as a proportion, between the peak and width of the tire.
R	Tire development	How the rubber is layered. Virtually at all times “R,” which suggests it’s a radial tire.
16	Wheel dimension	The diameter of the wheel (or rim) in inches.
92	Load index	A measurement of how a lot weight every tire can help. Consult with a load index chart for the overall weight allowed.
Y	Velocity ranking	The highest pace at which the tire can journey for an prolonged time. See pace ranking desk above.

What else your tires let you know

To this point, we’ve lined the fundamentals in the primary cluster of letters and numbers. However there’s extra data printed on different areas of the tire sidewall, together with:

• DOT code: The DOT (Division of Transportation) code is like an expiration date on your tires. Over time, rubber dries out and ultimately cracks. Specialists suggest that you just exchange tires which might be six or extra years outdated, even when they’ve loads of tread left. The four-digit DOT code signifies when the tire was manufactured. The primary two numbers stand for the week within the 12 months it was made, whereas the opposite two are for the 12 months. For instance, in case your tire has "1116" printed on it, then it was manufactured within the eleventh week of 2016.

• Most air stress: This quantity could be deceptive. Whereas it's the utmost air stress the tire can take — measured in kilos per sq. inch, or PSI — it's not the beneficial tire stress. For that, look in your proprietor’s guide or for the placard within the driver’s facet door jamb.

• Traction ranking: Graded as AA, A, B or C, this data charges a tire's traction — or stopping potential — in a braking take a look at on a moist street floor, as in contrast with different tires. AA signifies the most effective traction efficiency and C is the worst.

• Temperature ranking: This letter represents how a lot temperature the tire can stand up to. From finest to worst, the scores are A, B and C.

• Treadwear ranking: The phrase "TREADWEAR" on the facet of your tire is adopted by a quantity akin to 120 or 180. This tells how sturdy the tread is in contrast with an trade commonplace variety of 100. A tire with a 200 ranking ought to final twice so long as the trade commonplace.