Quote:
Originally Posted by DRivero
Okay, I have a silly question. I need tires. I've narrowed my choices down, but I'm stumped by something. My bike, as it came to me, has 100/80 16 front tire, and a 130/90 16 rear tire. I am quite short (slightly less than 5'2"). I'm not tippy-toeing on the bike, and I don't want to be, but some of the tires I'm looking at come in 100/90, not 80. So here is my question: since I already have a 90 on the rear, if I put a 90 on the front, will I notice, height-wise?
See, I told you it was a silly question.....
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My profs used to say, the only silly (stupid, etc) questions are those that go unasked...
Anyhow, to tire sizes. The stock rear tire was a 130/80-16 which works out to being 24.19" (nominal) diameter. Going to a 130/90-16 increases the diameter to 25.21" (nominal), which raises the axle by half the difference, 0.51", since half that extra diameter is above the axle. The seat is about 1/3 of the way from the rear to the front axle, so the seat would have risen about 3/8" more or less.
The stock front at 100/80-16 is 22.3" (nominal); going to a 100/90-16 increases the diameter to 23.09" (nominal), thereby raising the axle 0.4". The seat would go up about 1/3 of that, a little less than 1/8".
The net result is that it would be a little taller, but not that much and likely not enough to affect how your feet plant at a stop. Your speedo will read slower, so depending on how accurate it was before you'll need to be aware of its inaccuracies. The odometer will be more accurate.
Tire sizes broken down: 100/90-16. 100 is the tire width across the sidewalls in millimeters. /90 is a percentage of the width used to describe how tall the tire is from the bead to the tread. A /100 tire would be as tall as it is wide. A /50 would be half as tall as it is wide. -16 is the tire bead diameter, not the overall rim diameter. The recessed part of the rim where the tire rubber bead actually seats is the bead diameter.
Oh, most people perceive the height increase as much more than that typically because they're replacing a worn out tire missing a lot of tread thickness with a new tire that's larger in size. The axle very well could move up almost an inch in that case, but much of that lift is just replacing the worn away old tread thickness.
FWIW...