tire q

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tire q

Postby scheckaet » 03:19 pm Mar 09 2007

Can anybody explain to me what the tire specs mean?
80/100-21
100/100-18
I assume some of the bigger number are for diameter (but why 2 different #?), and the smaller sidewall height or tire width?.
help!
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Postby thebleakness » 04:42 pm Mar 09 2007

All right, lemme see if I get this right...

The first number (ie. 80/100...) is the tire width. Meaning that it is 80 mm wide. The second number (80/100) is the aspect ratio. The aspect ratio is the height of the tire divided by the width. In this case it would be 100%, meaning that the height and width are the same. The last number is the tired diameter, in the first example it would be a 21" diameter.

Thats the way I've thought it was, anyone correct me if I'm wrong.
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Postby xagentman » 05:00 pm Mar 09 2007

I always thought of it as: first number = tire width // second number = sidewall height // last number = rim size.

yes/no?

between the two of us we have the right of it. :)
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Postby scheckaet » 05:56 pm Mar 09 2007

:prayer:
it makes sense now.
thanks! Now I can buy new tires and KNOW what it means :partyman:
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jetting guide: viewtopic.php?f=105&t=1156
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Postby Indawoods » 06:39 pm Mar 09 2007

The bottom line is that the sizing of tires for certain motorcycles is determined by the factory motorcycle and tire engineers. They know their science well and know what works best on certain motorcycles. They have devised a numbering system which is used when replacing your tire. It is not a user-friendly numbering system but it makes sense to the tire manufacturers. For example a 100/80-18 tire means the 100 is the nominal width in millimeters. The 80 is the aspect ratio, and refers to the height of the tire as a percentage of the width (in this case 80 percent of 100mm). The 18 is the wheel’s diameter in inches for which the tire is designed to fit.
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