Best way of Measuring / Verifying offset
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Joined: Oct 2004
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From: Pensacola
Best way of Measuring / Verifying offset
I will be going to look at some rims with unknown offsets.
I know what offsets and widths the manufacturer made for this particular rim so a close measurement may be good enough. Say +- 5mm
Is there a best way to measure the offset?
I'm guessing that you need to know the width.
Measure from the inside hub mounting surface out to the inside of the wheel.
And subtract half the width.
As the actual width of the rim is the inside to inside flange measurement, how much should be allowed for rim thickness? Is this even an issue?
Am I even in the ballpark or is this just fuzzy math?
Assumptions: Wheels are not marked with offset. Wheels were on an S2000. Best guess is 48 for the fronts and 55 for the rears.
I have plent of tools to work with,
(just not mental)
I know what offsets and widths the manufacturer made for this particular rim so a close measurement may be good enough. Say +- 5mm
Is there a best way to measure the offset?
I'm guessing that you need to know the width.
Measure from the inside hub mounting surface out to the inside of the wheel.
And subtract half the width.
As the actual width of the rim is the inside to inside flange measurement, how much should be allowed for rim thickness? Is this even an issue?
Am I even in the ballpark or is this just fuzzy math?
Assumptions: Wheels are not marked with offset. Wheels were on an S2000. Best guess is 48 for the fronts and 55 for the rears.
I have plent of tools to work with,
(just not mental)
Registered User
Joined: Feb 2003
Posts: 38
Likes: 0
From: north shore
Originally Posted by dead-bird,May 28 2005, 11:07 AM
I'm guessing that you need to know the width.
Measure from the inside hub mounting surface out to the inside of the wheel.
And subtract half the width.
Measure from the inside hub mounting surface out to the inside of the wheel.
And subtract half the width.
Registered User
Joined: Jul 2004
Posts: 42
Likes: 0
From: Long Island NY
Alot of wheels have the offset cast right on the wheel. If it is a multi-piece wheel, it may not. What kind of wheel is it?
Start off by measuring the wheel width. This is the distance between the flanges - not the actual width of the whole wheel.
Next measure the backspace - the distance from the back of the wheel to the mounting pad. Be sure you are measuring from the back of the wheels outer flange - not the tire.
The width does not include the outer flange - but the backspacing does include the flange.
On a 18 x 7" wheel, 4 " of BS = 0 offset.
On a 18 x 7.5" wheel, 4.25 " of BS = 0 offset.
On a 18 x 8 " wheel 4.5 " of backside = 0 offset.
On a 18 x 8.5" wheel, 4.75 " of BS = 0 offset.
On a 18 x 9" wheel, 5" of BS = 0 offset.
Every 1/4 " of additional BS is basically 6-7mm. So 18 x 8 w/ 6.5" of BS would be about 52mm offset.
This either helped you or confused you even more. Email me if you need this clarified =)
Start off by measuring the wheel width. This is the distance between the flanges - not the actual width of the whole wheel.
Next measure the backspace - the distance from the back of the wheel to the mounting pad. Be sure you are measuring from the back of the wheels outer flange - not the tire.
The width does not include the outer flange - but the backspacing does include the flange.
On a 18 x 7" wheel, 4 " of BS = 0 offset.
On a 18 x 7.5" wheel, 4.25 " of BS = 0 offset.
On a 18 x 8 " wheel 4.5 " of backside = 0 offset.
On a 18 x 8.5" wheel, 4.75 " of BS = 0 offset.
On a 18 x 9" wheel, 5" of BS = 0 offset.
Every 1/4 " of additional BS is basically 6-7mm. So 18 x 8 w/ 6.5" of BS would be about 52mm offset.
This either helped you or confused you even more. Email me if you need this clarified =)
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