Picking out tires is a pain, trying to figure out which size may or may not work compared to stock.

This calculator helped me compare different sizes in diameter, width, sidewall, circumference, Revs per mile and speed difference.

Tire Size Comparison

 

IMHO the only way to know for sure is to measure a tire mounted on a rim of the width you'll be using it on, inflated at the pressure you intend to run.

 

They don't list any tires for Kawa, BMW, or Ducati..... guess pretty much useless.

 

I made my own calculator, but need to revise the formulas that disappeared when I transferred it from excel to google sheets to share it.

Many tire manufacturers give the inflated diameter on one of the recommended sizes of rims so you can learn how it will affect performance.

I can email a functional version that has the 09 KLX numbers for the gears/primary, but still need to fix the google version before making it available,

Edit: Fixed the Google Tire Size Comparison calculator. You can change the sprockets, to see what happens, you can change rpm, change tire diameter (mfr usually publishes this) but be careful if you change the circumference, you will be deleting the calculator, to see what it does to the speeds in gears, both mile and KM. I may do an if statement for the circumference to allow using it, but not right now.

I used it to compare tires for my KLX650 and Zephyr making it for 6 speeds and having two calculators in the page to compare tires and gearing. Works well with any bike you can get the primary/gear box tooth count, final drive and tire diameter. Then play with the rpm to see what speeds are.