How to Decipher Motorcycle Tire Codes

Understanding motorcycle tire codes is always a plus 1 photo
Even though most riders pay a visit to their bike dealer or local motorcycle tire shop when it comes to changing their bikes’ tires, I bet there are a lot of guys who would like to know more about the rubber they roll with.
Truth be told, it’s no rocket science decoding the data behind the symbols on a motorcycle tire, and one can actually live quite a happy life without knowing what those numbers mean (ignorance is bliss, they say), but I really believe that knowledge is power, so here we go.

There’s power in numbers and letters

Those of you who have no idea on what the markings of a motorcycle tire mean will definitely be surprised to learn how much information is contained in those codes. More than 10 different attributes of a tire are marked on the wall, and knowing how to read them can at times help you make a better decision prior to buying or mounting a specific tire on your bike.

Obviously, the biggest thing you’ll see on the tire wall is the name of the manufacturer. It’s of course very good for business to have people noticing your brand’s name and logo. The logos are usually big and easily readable, at least for people who know one or two things about tires. Additional markings, such as specific drawings and tire name can also be found near the brand name. For example, Pirelli Scorpion tires actually have a scorpion embossed on them, on both car and motorcycle versions.
However, while the brand of tires you’ll be using is important, there are way more important symbols on the tire, and their king is the tire size. The tire dimensions symbol cluster usually includes three groups of numbers and letters, separated by dashes or slashes. Markings such as 90/90-17 or 130-70-16 can be met, with slight variations which can eliminate the last dash or replace it with a letter, such as 170/60R16 or 170/60 16. All these methods of displaying the tire dimensions read the same variables, and getting used to them is really easy.

The first number, which usually starts at 80 for motorcycles and can reach high values, such as 320 or 350, determines the width of the tire and is expressed in millimeters. A tire sized 90/xx-xxx is 90 mm wide when inflated to the spec pressure, measured in a straight line “through” the tires from one edge to the other.

The second group of numbers denotes a slightly trickier concept, but again, it’s no rocket science. As the first was the width, you’ve probably guessed that the second one represents the height…and you’re right. However, this time we’re not dealing with a physical measure unit, but with an aspect ratio. The two digits represent how tall the tire is, compared to the tire width, in %. That is, a 130/70 mark stands for a tire that’s 130mm wide and 130 x 0.7 mm tall, which is 91mm.

Basically, the bigger the second number is, the taller the tire will be. And you’ll observe that sport tires have lower % markings, whereas the off-road and adventure/ dual-sport ones have higher values. Tire wall height influences weight carrying capacity, stability around corners and structural strength in certain scenarios, but the tire manufacturers are offering the right combination for the right purpose, anyway.

Finally, the last cluster ranges usually between 15 and 30, and expresses the diameter of the rim, in inches. Rear tires have smaller numbers, while the front ones have the bigger one. If you get sets of tires for your bike, you’ll most likely end up with some of the most common combinations, such as (rear then front) 15-17, 17-17, 17-21, 18-21 and more. Before deciding to buy new tires, taking a peek in your bike’s owner’s manual is a smart decision. Installing different size tires may not comply with your local road safety regulations and might cause your bike to fail the technical inspection.
The next important things you should take into account are the type of tire, tube or tubeless, the weight limit and the speed rating. Tires made especially for being used with tubes might not work too well with tubeless rims, whereas the opposite is possible. TT stands for Tube Type, while TL stands for TubeLess. Construction type is usually noted with either R or B, for Radial or Belt ply, respectively, and reveals the structure of the tire case. As always, it’s smart to stick with the owner’s manual.

Speed rating, or speed index, is especially important for riders who use to travel at higher speeds, on the highway or on the race track. The rating is marked with a letter and the reference table below explains the pattern. If you know you plan to ride your bike at higher speeds, choosing the corresponding version is both safe and smart.

L- max. 120 km/h (74 mph)
M – max. 130 km/h (81 mph)
N – max. 140 km/h (87 mph)
P – max. 150 km/h (93 mph)
Q – max. 160 km/h (99 mph)
R – max. 170 km/h (105 mph)
S – max. 180 km/h (112 mph)
T – max. 190 km/h (118 mph)
U- max. 200km/h (124 mph)
H – max. 210 km/h (130 mph)
V – max. 240 km/h (149 mph)
W – max. 270 km/h (168 mph)
Y – max. 300 km/h (186 mph)
Z –over 240 km/h (149 mph).

The max load is usually indicated in both kg and lb by most manufacturers, and this info is generally displayed next to another key safety element, tire inflation pressure. At the same time, a LI (load index) can be found on the tires, and the attached table will help you figure out their meaning. Riding with the right pressure in your tires has three major advantages: keeps you safe, doesn’t negatively affect mileage and prevents premature tire wear.

The “right” pressure is the result of painstaking testing carried out by the manufacturers, and you should not stray from these values. Your bike should also have a sticker somewhere, telling you the pressure you should run your tires at when riding with a passenger or when heavily loaded. Over-inflating or running a lower pressure for prolonged periods of time will wear the tire unevenly and excessively, increase fuel consumption, and in some cases, poor handling and pose a crash risk.

Finally, more codes to be considered is a 4-digit number usually associated with the DOT (Department of Transportation) letters. The first two digits represent the week of manufacture, while the latter two the year. For example, a DOT 1414 mark tells you that the tire was fabricated in the 14th week of the year 2014. Manufacturers guarantee that their tires retain their properties intact for up to 5 years from the date of manufacture, provided they are also stored properly. A visual inspection of the tire with an older “DOT” is a good thing, too.
Balance marks can be present on tires in the shape of small white, blue or red dots, and they indicate that the tire was balanced by the manufacturer. The technician mounting the tire should make sure to line up the valve with this mark, and should be looking for it on the wall or even inside the tire. TWI lettering or a triangle pointing up stand for Tread Wear Indicator, and tell the rider when it’s time to replace the tire.
When the wear indicator can be seen in the thread, the message is clear: the tire is very close to the end of its service life. You might also see an arrow on the tire wall: it indicates the rotation direction, and tells the way the tire should be installed for optimal performance and water dispersion.

Now, that you know the secrets of the motorcycle tire codes, and can spread the knowledge with your buddies. Follow these links for a more detailed guide on how to choose motorcycle tires:

A Guide to Motorcycle Tires: Part 1
A Guide to Motorcycle Tires: Part 2
A Guide to Motorcycle Tires: Part 3.
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