 Backspacing, what am I missing? |
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| McMark |
 Jun 25 2006, 06:30 PM
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#1
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914 Freak!  Group: Retired Admin Posts: 20,179 Joined: 13-March 03 From: Grand Rapids, MI Member No.: 419 Region Association: None  |
Somehow all of the "guides" for finding back spacing and offset don't seem to make sense between their examples and their formula.
This site for example. In their chart they list a 5.5 wheel with 3.75 back spacing as having a 12 mm offset. They say to find the offset that you subtract centerline (5.5 / 2 = 2.75) from back spacing (3.75). Which gives us (3.75 - 2.75) 1 inch. Which converts to 25.4 mm, NOT 12 mm. What I'm I missing? |
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| Demick |
Jun 25 2006, 08:58 PM
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#2
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Ernie made me do it! Group: Benefactors Posts: 2,312 Joined: 6-February 03 From: Pleasanton, CA Member No.: 257  |
pupwag has it right. A 5.5" wheel is 5.5" from bead to bead (rim width in their diagram). You cannot accurately determine backspace from offset by just knowing the bead-to-bead width. You need the overall wheel width. Without it, you can just approximate what the backspace is (or offset is). Which is exactly what that table does.
For the most part, I have seen the wheel flanges to be around 3/8" wide for an alloy wheel. Looks like their table assumes about 1/2" wide wheel flanges, which is where your missing ~13mm comes from. Demick |
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Posts in this topic
McMark Backspacing Jun 25 2006, 06:30 PM
Jeroen you're missing nothing... their table is just ... Jun 25 2006, 06:47 PM McMark WTF, that's the SECOND site I've seen with... Jun 25 2006, 06:51 PM trekkor Welcome to the internet :)
Didn't someone say... Jun 25 2006, 07:07 PM pupwag Might be that the 5.5 is bead to bead and backspac... Jun 25 2006, 07:26 PM
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