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Diameter difference:110-90 and 120-90?
- bountyhunter
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I was wondering how much it would increase going to 120-90-18?
If I understand the way they spec them, the diameter would increase about 0.4" more on each side or a total of maybe 0.8" diameter across the wheel.... which is about 3%.
Is there a table that shows the diameters on various tire sizes?
1979 KZ-750 Twin
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- trianglelaguna
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- New and improved - extra strength
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- kano
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so 5 more mm Tyre each side.
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- RonKZ650
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321,000 miles on KZ's that I can remember. Not going to see any more.
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- steell
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A 120/90/18 of one brand will not have the same dimensions as the same size tire of a different brand. Some of the tire manufacturers websites will give you the dimensions of the various size tires in different models (a 120/90/18 tire is not even consistent in size across the same manufactures model line).
It wouldn't surprise me if you found a 110/90/18 tire from one manufacturer that is larger than another manufacturer's 120/90/18.
When I was playing around racing sports cars, I went to the dealer and measured each tire until I found four that matched. And this was one model tire from a specific manufacturer.
Crazy, isn't it?
KD9JUR
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- bountyhunter
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A stock 4.00-18 is close to a 120/90 in diameter, but narrower.
I found that out the hard way. My bike came stock with 4.00-18 tire and 16/38 gears which is WAY too low. I bought a new chain and gears of 17/38, but the RPM are still same as original setup because the 110-90 tire I have to use is smaller diameter. I ran a 120 tire once but the center strip burned out faster because the rim is too narrow and that pinches the sidewalls in and pooches out the center of the tread so it isn't the correct profile. The 100 tire got considerably better tread life.
These metric tires really are not the right fit.
1979 KZ-750 Twin
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- bountyhunter
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I don't understand how that's possible because the reference at the top of this forum section says that the "110"mm is the tire width and the 90 is the percent aspect ratio (the percent of the width that the height of the tire is). If you specify the width and the aspect ratio, that should define the height of the tire. Add two heights to the rim diameter and you should get the wheel diameter.It wouldn't surprise me if you found a 110/90/18 tire from one manufacturer that is larger than another manufacturer's 120/90/18.
Based on my tire, it works: the rim diameter is 18", the tire is 110/90 which means the width is 110mm = 4.3". Multiply times 90% and you get a height of 3.9". Twice that is 7.8" and added to the 18" rim diameter you get 25.8" which is the diameter I measured on my tire.
1979 KZ-750 Twin
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- steell
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Think of the tire numbers as a "class" and the different diameters/etc as variations within that "class".
Dunlop D404:
100/90-19 - 2.15 - 25.82 - 3.90
Dunlop GT501:
100/90-19 - 2.15 - 26.12 - 4.05
Tire size- rim width- diameter- section width
And that's two tires of the same size from the same company.
www.dunlopmotorcycle.com/tirecatalog_category.asp?id=3
So lets take a look at the rear.
Dunlop 404
120/90-18 - 2.75 - 26.44 - 4.76
Dunlop GT501
120/90-18 - 2.75 - 26.50 - 4.75
Closer on the rear.
GT501 is not available in 110/90/18, but the 404 is.
110/90-18 - 2.50 - 25.51 - 4.41
Compare that to your measurements.
Differences can be even larger when comparing two different manufacturers.
I had nothing to do with it being this way, it's just something I ran across years ago
KD9JUR
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- Lorcan
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And yes, Steell, sometimes I pump them up...:laugh: :blush:
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- bountyhunter
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1979 KZ-750 Twin
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