Ok, what do the numbers on the tires stand for? On an ATV it is simple, a 22-11-8 tire is 22" tall, 11" wide, and is on a rim that has an 8" diameter. Is there an equivalent system for a motocycle tire?

For example if a tire has a size 3.50 S19-4PR I would assume it has a width of 3.50" and a rim diameter 19" but now how do I know the overall height of the tire?

EDIT
This should help
http://www.motorcycle-karttires.com/charts/sizedesign.asp
END OF EDIT

The numbers on a bike tire work the same as they do on a car.

My rear bike tire is 130-90-16 ( Width - Profile - Rim Size )

130 is the width of the tire in mm. It is therefore 13 cm wide or ~5"

The next number is the profile - Profile is the sidewall height as a percentage of the tires width. A 100 profile would have the same sidewall height as the width of the rubber. My bike has a 90 - which is pretty common for older bikes - the newer bikes have more horsepower and tend to need lower profile tires - less sidewall to flex. More sidewall means that you get a bit softer a ride (more sidewall flex) and for some reason lower chance of hydoplaning... I've still to come up with proof or evidence on that one so consider that last point iffy at best - secondhand news.

The last number is the rim size. My bike has a 16" rim on the rear. The front is a 19 inch rim - so the last digit of my rear tire is 16, and on the front tire it is 19.

hope that helps,
woot.

Ah yes - other measurement systems than we normally see for bikes. Older bikes <80 and Harley's like to use different imperial systems. I see that size is for the front o an xs650. The rear tire is listed as 130/9OS 16-4P R (or a S rated 130-90-16 tire... )

I searched and found nothing on how to decifer it. :-/ I tried and still am trying.

Ok thanks Woot that helps a lot. I have been searching too and found this site which has some good charts http://100megsfree4.com/honda/tire.htm .