You can find the tire size on the sidewall of your tire
205 - Nominal section width in mm.
The width of the tire on a standard rim.
55 - Aspect ratio in %
The height of the sidewall in % relative to the section width
R - Construction of the Tire (R=Radial)
16 - Rim diameter
91 - Load Index (e.g. 91 = 1356 lb)
An index code for the maximum load capacity of the tire.
W - Speed Index (e.g. W = 168 mph)
An index letter for the maximum speed of the tire.
Additional codes can be “C” (Commercial tires for vans, trucks, buses) and “XL” (for higher load index)