Tire size changes

[KnightofNi]

so I know that the numbers are the ratio of sidewall height to width, but I'm not sure how it works.

my fav tire for the XR has been discontinued and I need to find new ones. one of the ones i'm looking at (because it has such good reviews) comes in sizes just off from what I need

I need a 90/90 front and a 110/90 rear. the tire in question comes in 80/100 front and 110/100 or 120/90 rear.

my question is "assuming i have enough clearance to run a wider tire, would the 120 work better than the 110, and exactly how much wider/taller will the tire be?
also, wshould i even bother trying the 80/100 front?

[Desmo Demon]

I need a 90/90 front and a 110/90 rear. the tire in question comes in 80/100 front and 110/100 or 120/90 rear.

my question is "assuming i have enough clearance to run a wider tire, would the 120 work better than the 110, and exactly how much wider/taller will the tire be?

I don't know about handling for that bike, but IIRC, a 90/90 is 90mm wide and 90 x 0.90 = 81mm tall. A 110/90 would be 110mm wide and 110 x 0.9 = 99mm tall, so.....

An 80/100 would be 80mm wide and 80mm tall (10mm narrower - 5mm less on each side, and 1mm shorter than stock)
A 110/100 would be 110mm wide and 110mm tall (20mm wider - 10mm on each side, and 19mm taller than stock)
A 120/90 would be 120mm wide and 108mm tall (10mm wider - 5mm on each side, and 9mm taller than stock)

I believe my math to be correct.

[KnightofNi]

Thanks! 
i figured out the formula...the first number is the width, the second number is the height of the tire represented as a percentage of the first number.
i.e. - a 90/90 would be 90mm wide and the sidewall is 90% of 90mm which is 81mm.




i don't think i want to go to a narrower tire up front. i'll keep that one the same and measure the rear to make sure I have clearance.