I think all of us can read the tire sizes on the side walls, but do you know what all those other numbers and letters mean? There is a lot of information there, but it’s all in code. Let’s start with the size. Do you have an older bike and your tire just has a dash (-) between the width and aspect ratio? That means something! It’s the construction code and here’s the brake down:
Now how old it is? Find the DOT number, then look at the last four digits. They represent the week and year of production. For example, a date code of “4510” means the tire was produced in the 45th week of 2010.
One of the more critical marks on a motorcycle tire is the rotation arrow(s). Always insure the tire is turning the proper direction for best traction and water dispersal.
Next is the max inflation allowable by the tire manufacture. This is for a cold tire carrying its max load, and may not be the recommended pressure by the motorcycle manufacture for your load. Check your owner’s manual for that.
Now let’s check the tire’s load rating and speed. Find a two digit number and letter not part of the DOT number. The number is the max load rating at max pressure, and the letter is its max speed rating. Note that tires with a “W” or “(W)” speed index are identified by a “Z” before the construction code in the tire size designation. Also if one intends to run at or near the max rated speed, then max load must be reduced.
Speed Index Chart:
|
Rating
|
Speed: miles per hour
|
Speed: kilometers per hour
|
|
Q
|
99 mph
|
160 km/h
|
|
S
|
112 mph
|
180 km/h
|
|
T
|
118 mph
|
190 km/h
|
|
U
|
124 mph
|
200 km/h
|
|
H
|
130 mph
|
210 km/h
|
|
V
|
149 mph
|
240 km/h
|
|
W
|
168 mph
|
270 km/h
|
|
(W)
|
Over 168 mph
|
Over 240 km/h
|
|
Y
|
186 mph
|
300 km/h
|
|
Z
|
Over 149 mph
|
Over 240 km/h
|
Just two more things; don’t forget to check for those ware bars as you use up the tread. But the most important thing you can do for your tires is, inflation, inflation, inflation! Get a good gage and use it often for best traction, and tread life.
Happy New Year – Ride Safe!
Steve Kesinger, your Safety Guy!
