T O P I C R E V I E W
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166 Merlot
Member # 1549
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posted
For example on this wheel right here:
(edit: well I guess you know both variables here, but lets just say you only knew the offset)
Chrome Saleen
if +28mm offset is about 1.1 inches, and half of 18x10 (wheel centerline) is 5" then why why isn't 5"+ 1.1"= 6.1" the backspacing listed on their website? BS listed: 6.6"
Does anyone follow? Am i making sense? Yarada-tadada?
i noticed this on a couple different sites, sometimes the math makes sense, but it usually doesn't. Please help thanks. [ July 14, 2010, 05:23 AM: Message edited by: 166 Merlot ]
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SteveL
Member # 1241
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posted
Because they are not measured from the same point.
Backspace is measured from the outermost lip of the rim in towards the hub mount. It includes the part of the rim that sits outside of the tire bead (which is typically 1/2" thick).
Offset is measured between where the tire bead sits which is inside the lips of the rim. A 0 offset 10" rim will have a backspace of 10/2= 5 inches + another 1/2" for the part of the rim that's outside the tire bead.
A 10" wide rim is actually about 11" wide. 10" is the distance between the tire beads and 11" is the overall width of the rim including the inner and outer lips. [ July 14, 2010, 08:52 AM: Message edited by: SteveL ]
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copcar
Member # 10113
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posted
You forgot the 1/2" for the lip.
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166 Merlot
Member # 1549
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posted
Ok I see what you guys are saying, but what about this one:
Chrome saleen 2
math makes sense on this one? I found a wheel I like but the dude won't email me back as to what the BS is... I don't want to be off by even a 1/2" cuz I'm already pushin it on the clearance.
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SteveL
Member # 1241
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posted
It's 9" wide between the tire beads. Half that is 4.5" to the centerline. The offset is +0.9" so the mounting plate is 4.5+0.9 = 5.4" in from the inside tire bead. Assuming 0.5" for the lip so the backspacing is 5.9". The math works.
Regardless, you have a different problem. You found a rim. You don't know what it's backspacing is and don't know if it will fit. No one can answer that.
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166 Merlot
Member # 1549
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posted
quote: Originally posted by SteveL: It's 9" wide between the tire beads. Half that is 4.5" to the centerline. The offset is +0.9" so the mounting plate is 4.5+0.9 = 5.4" in from the inside tire bead. Assuming 0.5" for the lip so the backspacing is 5.9". The math works.
Regardless, you have a different problem. You found a rim. You don't know what it's backspacing is and don't know if it will fit. No one can answer that.
I think you just did. Thanks for the help
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68dustin
Member # 5388
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posted
http://www.rimsntires.com/rt_specs.jsp
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166 Merlot
Member # 1549
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posted
quote: Originally posted by 68dustin: http://www.rimsntires.com/rt_specs.jsp
That's what's up right there. Got me a new bookmark.
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