cinco
XS400 Member
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What is the largest rear tire possible on an 18" mag wheel with disc?
Background: Looking at maybe swapping my wheel set-up from spokes to mags. I have on hand a 1979 18" rear disc mag and a 1979 disc swing-arm on the way.
- Current rear set-up: 2.15 x 16 front wheel & 120/90-16 tire & drum (1980 Special II)
- Possible mag rear set-up: 1979 rear disc swing-arm & 1979 2.15 x 18 mag
Resources: I've been using the following reference guides to try and get a better idea of fitment:
- "Rim to Tire Application" (Thanks Drewpy!): http://www.dropbears.com/u/utilities/tyrerim.htm
- "Motorcycle Size Conversion Chart": http://www.kgmotorcycletires.com/size_conversion_charts.htm
- "Motorcycle Tire Diameter Calculator": http://www.rbracing-rsr.com/tirediamcalc.html
- "Millimeters to Inch Conversion Calculator": http://www.metric-conversions.org/length/millimeters-to-inches.htm
Tire Comparision: From using the above resources here's what I've found...
- 120/90-16 Tire = 24.5" Diameter & 4.72" wide
- 110/90-18 Tire = 25.8" Diameter & 4.33" wide
- 120/90-18 Tire = 26.5" Diameter & 4.72" wide
What I've seen others talk about using:
Drewpy & Others - 4.00x18 = roughly 110/90
What I'm thinking:
- My existing 16" rim using the 120 wide clears my chain just fine - others have said a 130 wide on the 16" rim hits the chain - which looks correct.
- Theoretically a 120 wide tire on an 18" mag should also clear the chain - BUT - may hit on the inboard side of the swing-arm due to the increased diameter and the way the shape of the swing-arm is "stepped".
- Drewpy reports the 4.00x18 (110/90x18) fits. A 120/90x18 would mean a diameter increase of .7 inches and a width increase of .39 inches.
Whew - Just trying to provide some resources while explaining my thought process. Thus, to make a long quesstion short... Anyone actually using a 120/90-18 on a disc mag/swingarm?
And thanks for your time and advice Oh yeah - cold beer on me when we meet!
Background: Looking at maybe swapping my wheel set-up from spokes to mags. I have on hand a 1979 18" rear disc mag and a 1979 disc swing-arm on the way.
- Current rear set-up: 2.15 x 16 front wheel & 120/90-16 tire & drum (1980 Special II)
- Possible mag rear set-up: 1979 rear disc swing-arm & 1979 2.15 x 18 mag
Resources: I've been using the following reference guides to try and get a better idea of fitment:
- "Rim to Tire Application" (Thanks Drewpy!): http://www.dropbears.com/u/utilities/tyrerim.htm
- "Motorcycle Size Conversion Chart": http://www.kgmotorcycletires.com/size_conversion_charts.htm
- "Motorcycle Tire Diameter Calculator": http://www.rbracing-rsr.com/tirediamcalc.html
- "Millimeters to Inch Conversion Calculator": http://www.metric-conversions.org/length/millimeters-to-inches.htm
Tire Comparision: From using the above resources here's what I've found...
- 120/90-16 Tire = 24.5" Diameter & 4.72" wide
- 110/90-18 Tire = 25.8" Diameter & 4.33" wide
- 120/90-18 Tire = 26.5" Diameter & 4.72" wide
What I've seen others talk about using:
Drewpy & Others - 4.00x18 = roughly 110/90
What I'm thinking:
- My existing 16" rim using the 120 wide clears my chain just fine - others have said a 130 wide on the 16" rim hits the chain - which looks correct.
- Theoretically a 120 wide tire on an 18" mag should also clear the chain - BUT - may hit on the inboard side of the swing-arm due to the increased diameter and the way the shape of the swing-arm is "stepped".
- Drewpy reports the 4.00x18 (110/90x18) fits. A 120/90x18 would mean a diameter increase of .7 inches and a width increase of .39 inches.
Whew - Just trying to provide some resources while explaining my thought process. Thus, to make a long quesstion short... Anyone actually using a 120/90-18 on a disc mag/swingarm?
And thanks for your time and advice Oh yeah - cold beer on me when we meet!