In the above graphic tire size is 120/70 zr 17.
Section Width = tire width in millimeters - 120 mm.
Aspect Ratio - This indicates the ratio between the tire's width and height. In this case, the height of the tire is 70% of its width or 84mm.
Rim Diameter - in this case 17 inches.
Speed Rating - in this case the speed rating is Z which is equal to a speed rating of over 149mph.
Construction - R = Radial
130 = width in mm.
90 = aspect ratio of 90% of width = 117mm
16 = Rim size of 16 inches
67 = Load rating (A numerical code which corresponds to the total load carrying capacity at the speed indicated by the speed symbol)
M = Motorcycle
T = Tire Width Code
90 = Aspect Ratio
16 = Rim Size
B = Load Range
LOAD AND PRESSURE
Load index may be expressed either as a numerical code or a letter code. Most of the time manufacturers will provide the max load information on the sidewall so there's no confusion.
In this instance the maximum load is 520 lbs. This is the weight the tire is capable of handling when it is properly inflated.
The maximum tire pressure is indicated. But you should only fill a tire to the MOTORCYCLE manufacturer's recommended level. Overfilling can lead to premature wear and poor handling. Also measure the pressure when the tire is cold. Measuring when hot will skew the numbers.
Most tire manufacturer's have websites which will provide information on the recommended pressure for each motorcycle. You can also check your owner's manual or contact a local dealer.
Tire Diameter =
(Section Width X Aspect Ratio X 2 / 25.4)+ Rim Diameter
Ex. 130/70 R18
130 x .7 x 2 = 182 / 25.4 = 7.165 + 18 = 25.16 inches
|TREAD WEAR AND MFG DATE:
Tires will also have a USDOT id and will indicate the week and year of manufacture. (See above). Prior to 2000 there were only three digits with the last on being the year.
Some tires may have raised triangles, or the letters TWI, to show where the tire wear indicators are in the tread. When these marks are equal to the tread, it's time for new tires.Additionally the sidewall may also include "tubeless" or TL, "tube type" or TT, and the tire composition, materials, ply etc.
Pictures Courtesy of AMA.