Wheel Backspace and Offset

[JCStewart]

I did a search and found some info but I need to know a couple of things

1. ) what is the differance between offset and backspace?

2. ) what is the factory alloy 17X8 wheel offset and backspace?



I am converting my dually to a SRW. I know I know... . not worth the time and everthing else... . I have seen those threads too. But I am putting a flatbed on and it will never show. The front tires will be the same as a factory SRW and the rear tires center to center will be 4" wider (just 2" on each side) than a factory SRW. I used a factory dodge wheel to get all these measurements and now I have to find out what offset/backspace the factory wheel is so I can try to get close to the same or narrower. I plan on running the factory 235/80R17 Goodyear tires so clearance wont be a problem. I have found a couple of wheels I like one is a 17X9 with a 4. 5 backspace and a -12 offset the other is a 17X8 with a 4. 5 backspace and +2 offset. Any suggestions

 

[cummins_crewcab]

I'm interested in this as well. I'm converting the front of my dually to SRW (removing dually hubs) but keeping the duals in the rear. Reason being that personally I think most aftermarket dually style front wheels are ugly so I want to run a regular style rim in the front and a matching series dually wheel in the back. I'll have to carry two spares but oh well I'll get over it, or maybe one spare and the dually hub...

 

[nickleinonen]

I used a factory dodge wheel to get all these measurements and now I have to find out what offset/backspace the factory wheel is so I can try to get close to the same or narrower. I plan on running the factory 235/80R17 Goodyear tires so clearance wont be a problem. I have found a couple of wheels I like one is a 17X9 with a 4. 5 backspace and a -12 offset the other is a 17X8 with a 4. 5 backspace and +2 offset. Any suggestions

the factory 8" wide wheels have 6" backspacing and offset you can calculate based off that [i don't ever use offset as it is easier to calculate wheel fitment with backspacing i think] - it would end up being something along +38mm [that is with adding the width of the wheel bead area, which ends up making an 8" wheel nearly 9" wide from outer edge to outer edge]



a 235/80 tire i would never mount on something wider than a 7" wheel. i don't think you even suscessfully mount one on an 8" or 9" wheel

 

[JCStewart]

My dually has 235/80R17 on it from the factory. It has the off road tire option they are Goodyear. Although they are on a dually rim... . and it may not be 17X8. I had not thought of that. I will have to go measure the dually rim.



I dont want to get any wider since the rear will be 2" wider anyway. But if my febal mind understands this correctly the factory is a 6 inch backspace and the wheels I am considering are a 4. 5 backspace, then it would get me 1. 5" of the 2" back. So I would be within 1/2" of the factory SRW on the rear. If the above is correct then I could go with a 285/70R17 or 285/75R17, if there is such a tire. But that backspace would move my front tires in closer too. So will they rub? Will I get the "Death Wobble"? Just so I am clear... . I dont like anything with the word "death" in front of it!



Help me soon, they are supposed to start building my super cool flat bed Monday. I have to let them know some demisions.

PS you can see my super cool flat bed here

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[JVolpe]

I am getting confused with this thread, but I think you are thinking backwards.



A wheel with less backspace than stock will stick out farther. Of course now I might be too confused to answer.

 

[Spooled-up]

A picture is worth a thousand words

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[bpenrod]

I am getting confused with this thread, but I think you are thinking backwards.



A wheel with less backspace than stock will stick out farther. Of course now I might be too confused to answer.

I don't think you are confused! Less backspace means a wheel of equal width will stick out more than one with more backspace.

 

[JVolpe]

Thanks, glad I was on the right track. I have my 315s on stock 17x8 wheels so that the tires don't stick out too much. I will look at the new CenterLine CrossFire 17x8. 5 with supposedly Dodge Ram 2500/3500 backspacing close to stock.

 

[JCStewart]

Ok Thanks for the info... your right a picture is worth a 1000 words. . maybe more. And I was going the wrong way with my calculations. The 4. 5 backspace would move me out to 3. 5" wider on the rear axle.



I am just going to purchase a set of factory alumium wheels and be done with it. If someone has a set they want to sell that are in REALLY good condition let me know. I dont want the factory steel/chrome. I want the alum or mag or whatever it is.

 

[JeepinDoug]

Thanks, glad I was on the right track. I have my 315s on stock 17x8 wheels so that the tires don't stick out too much. I will look at the new CenterLine CrossFire 17x8. 5 with supposedly Dodge Ram 2500/3500 backspacing close to stock.

Those are nice wheels but I don't see 8 lug listed on their site.

They are 17/8. 5/6"BS.

 

[JVolpe]

CenterLine Cross Fire 8 Lug 17x8.5

Another member, maybe another forum, was sent an email from CenterLine on the availability and this picture. He had emailed them for info on comparable 17" wheels with backspacing close to stock. He said the email quoted $199 each, I have not called Center Line to confirm yet.



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[WoodChuck]

The factory wheels (17 x 8) have a +45 offset, 6 5/16" B. S. and are 9 1/8" wide on the outside of the beads.