Height difference in rear tires sizes?
What is the height difference between rear knobby tires and advantage/disadvantage between these tires?
Our stock tire was 120/100/18 but we were thinking about replacing
with a 120/90/18 (lower profile) tire to lower the bike a little? We were told the original tire holds more air because it's a little taller and therefor rides better. We are now confused on what to do, can you shed light on this dilemma? Height difference?
MotoSport Staff 1 month 13 days ago Location: Portland, OR, USA
The second number is actually an aspect ratio measurement. This number references the overall height of the tire from the bead to the tallest point in the center of the tread. This number does not actually represent the height of the tire in millimeters, but rather a percentage of the width. On the tires you are looking at here the 120/100-18 the sidewall height is 100% of the tire width so it would have a 120mm sidewall height. On the 120/90-18 the sidewall height would be 90% of the tire width, approximately 108mm. So there really is only a difference of around 12mm in the sidewall height. Both tires would have the same width obviously but with the taller sidewall on the 120/100-18 the tire would have a flatter profile and have a bit more of a contact area with the ground. The 120/90-18 would have a rounder profile which may make the bike have a bit more maneuverability in the rear but with less contact area with the ground the handling of the bike may be less stable. Honestly it is such a small difference between these 2 tires that it would more than likely be hard to tell the difference when riding. I'd say it would be best to stick with the stock sized 120/100-18 as that KTM 500 XCW would benifit from the wider "footprint" of the tire.