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Old 11-27-2015, 02:59 PM
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Wheel Offset vs. Backspacing

I hope you can help. After researching, I am still somewhat confused as to how I can determine if a SRT rep or another wheel will fit properly on my Altitude. I know my stock 20" wheel has an offset of 56.4. I've seen wheels referencing backspacing instead of offset. Is there a formula out there that spells out how a given offset = a given backspacing?

I intend to install a set of RM Mids & Bilstein 4600s along with a set of 1.5" Bora spacers soon.

How can I be sure a wheel set I am interested in will indeed work with these upcoming suspension mods?

Thanks

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Old 11-27-2015, 06:03 PM
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Re: Wheel Offset vs. Backspacing

Back in the late 70s, through the mid 80s, I used to sell custom wheels and tires, in order to finance my automotive hobby. And I'll be the first to say, that MANY times, I wished the wheel manufacturers would use EITHER backspacing OR offset, BUT NOT BOTH!!!


I'll try to help......

Backspacing is the dimension that's measured from the back side of the wheel's mounting pad, to the outer edge of the back of the wheel.

Offset is the dimension between the backside of the wheel's mounting pad, and the centerline of the wheel. This gets tricky, but let me use an example, to try and illustrate this.

A rim might be called an 8" wide rim, for example, but that isn't the OVERALL width of the rim. The overall width of the rim is closer to 9", because the inner and outer beads add about another inch. The "centerline" of the rim, measured from the outermost edge, therefore, it would be 4.5". IF the backside of the mounting pad is 4.5" from the back edge, then the wheel has "zero" offset.

If the mounting pad was 5" from the back edge, the wheel would have 1/2" positive offset. If the backside measurement was 4", the wheel would have 1/2" negative offset. Problem is, because most of the wheels are now made in places other than the USA, the offset measurement is expressed in a metric number, which is confusing for many of us.....
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Old 11-27-2015, 06:18 PM
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Re: Wheel Offset vs. Backspacing

Thanks. I was able to piece that together from my research as well. The offset on my wheels are metric as well. I suppose, with some metric to imperial conversions, I could figure things out. Some cases the seller doesn't specify which units their number represents. Maybe someone here that has had a number of wheels over time can jump in and say, "any 9" wheel with X to X offset will work".
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Old 11-30-2015, 04:51 PM
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Re: Wheel Offset vs. Backspacing

uploadfromtaptalk1448920253684.jpg
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Old 11-30-2015, 05:07 PM
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Re: Wheel Offset vs. Backspacing

Quote:
Originally Posted by indydof View Post
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Old 11-30-2015, 05:34 PM
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Re: Wheel Offset vs. Backspacing

This web site (provided by one of the JeepGarage members) helped me a lot in trying to figure out what size & offset I could go with.


Once you know the style wheel you're looking for...the guys on this forum can verify the fit for you.....someone will have done it already & will chime in.


Online Wheel and Tyre Fitment Calculator. Offset, Tyre Stretch and Speedo Error | Will They Fit
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Old 11-30-2015, 05:46 PM
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Re: Wheel Offset vs. Backspacing

Thanks, I've actually used that site before when getting new wheels & tires for one of my other cars.
Don't no why I didn't go back to it...

Stock altitude wheel is 57.4 offset (I believe). The 2 styles I'm looking at are 34mm & 37mm. Both choices would push my tire away from the strut, which is what I wanted to be sure of.

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