Difference between back spacing & offset - Team Camaro Tech
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post #1 of 5 (permalink) Old Oct 16th, 11, 04:43 AM Thread Starter
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Craig
 
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Difference between back spacing & offset

I'm looking at getting bigger rims for the back & want to go to a 17"x 9.5" rim & on the sticky it says that a BS of 5.5 is the go but what is the difference between back spacing & offset.
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post #2 of 5 (permalink) Old Oct 16th, 11, 06:17 AM
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Re: Difference between back spacing & offset

Backspacing is the measures distance from the mounting face of the wheel to the rearmost surface of the inside bead. This is good for knowing distances to the suspension etc. It is essentially half of the wheel width, plus approx 1/2" (depending on the thickness of the wheel lip itself).

Offset is the difference between the wheel mounting flange & the center of the tread. Offset is great for comparing 2 different wheels, as you will know where the tire is in reference to the wheel mounting surface.

For example an 8" wheel with zero offset has 4" in either direction from the wheel mounting face. It could have 4-3/8" to 4-5/8" backspacing bepending on wheel thickness.

Years ago backspace was measured at the inner bead, leading to a lot of confusion. I think the main reason for change was the newer cars with positive offset wheels. Now the wheel is closer to the suspension, making this dimension more critical.
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post #3 of 5 (permalink) Old Oct 16th, 11, 07:39 AM
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Re: Difference between back spacing & offset

This site has great graphics for those of us that need a visual to help understand the difference:
https://www.rsracing.com/tech-wheel.html#backspace


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post #4 of 5 (permalink) Old Oct 16th, 11, 10:30 AM
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Re: Difference between back spacing & offset

Offset is where the wheels mounting pad is in relation to the centerline of the wheel (+ or - __ mm).

Backspacing is where the wheels mounting pad is in relation to the inner edge of the wheel.

Offset is metric and backspacing is standard measurments... The chart on the link Brian provided is a great cross reference.

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post #5 of 5 (permalink) Old Oct 16th, 11, 12:27 PM Thread Starter
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Craig
 
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Re: Difference between back spacing & offset

Thanks Guys
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