General Tyre / Tire Information

Wednesday, July 21st, 2010 Tech Articles 2 Comments

General Tyre / Tire Information

More information can be found on these wikipedia pages wiki/Motorcycle_tyres and wiki/Tire_code

Tyre / Tire size

Metric Sizing

I will only list the metric sizing as it is most applicable to sport bike wheels

190/50 17 means the tire is 190mm wide on a 17-inch rim with an aspect ratio of 50. This method is called “metric,” even though the rim size is in inches. The aspect ratio is the height of the side wall and it is a percentage of the width. i.e. 190/50 is 190mm wide and has a height of 95mm (190mm X 50%). A 190/55 tyre is 190mm wide with a height of 104.5mm (190mm X 55%).

Letters that show up elsewhere in the tyre sizing show speed rating and construction of the tyre; for example, R or B means the tire is radial or belted-bias construction, and Q, S, T, U, H, V, W, Y and Z indicate maximum speeds the tire can handle.

Speed Rating Chart

Letter	mph	km/h
H	130	210
V	149	240
W	168	270
Z	over 149	over 240

Date of Birth

When tyres are manufactured, they have their birth date molded into the side wall. It is a 4 digit number with the first two digits being the week number and the second two being the year, that is WWYY. Because rubber is organic, tyres deteriorate with age, for me it is important to buy the newest made tyres available. (My tyre man used to laugh at me as I went through them all on the rack to get the youngest set).

190/50 vs. 190/55 the 5% difference

Here is a scan of an article out of a magazine talking about the 5% difference between the 190/50 and 190/55 series tyres. I personally run a 190/55, once I tried one, I never went back. Some people run a 180/55 on a 6″ rim, saves some money, but the 190/55 is the best of both worlds. Sharper profile for easier turn in and maximum contact patch for grip.

Click the image for a larger readable copy