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Wheel Offset Advice

SLong

By SLong
in Tires, Wheels & TPMS

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SLong Enthusiast

SLong

Posted
Posted

Guys, I think I've decided to get a set of XD Monsters for my 2011 Z71. I have the 18" stock wheels on my truck now, and 265/70/18 tires. These tires are pretty tall but stock width, so I like the idea of pushing them a little further to the outside of the wheel well. I have zero knowledge about rims as I've never bought a set of aftermarket rims before.

 

Does anyone know the offset of the stock 18" rims that I currently have. I looked online and saw that the Monsters come in a -12 offset in the 18s. Does anyone have any idea how far this rim will push the tire out? I'd like to push them only 1/2" or so further out. Thanks in advance for any help.

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SLong Enthusiast

SLong

Posted
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Posted

Guys, I've done some research and found out the stock 18s on my truck have an offset of +31mm. The Monsters come in +33, +18 and -12. The +18mm, 18x9 sounds like it may be the way to go. Since there are 25.4mm in an inch, they should stick out a 1/2" past where the stocks one do with the same tires, if the stock rims are in fact 18x9. Does anyone know if the stock rims are 18x9? If they are 18x8.5, I guess that would mean that the tires would be pushed out another 1/2"????

cparks555 Senior Enthusiast

cparks555

Posted
Posted

I used to roll on 18x9 +18 Monsters, the following pic will show you how much they will stick out. I think the factory 18's are like 18x7.5, not completely sure though.

001.jpg

008.jpg

SLong Enthusiast

SLong

Posted
  • Author
Posted

Thanks, what tire and tire size was that in the pic? I'd like to look up the specs on that tire and see how wide they are and use the width of my tires to determine how much less mine will stick out. My tires aren't as wide as yours in the pic.

SLong Enthusiast

SLong

Posted
  • Author
Posted

Thanks, does that mean I can expect the tires to be pushed out a full 1.5" from where they currently sit? A 1/2" for the change from +31 offset to +18 and another 1" from the change from an 8" rim to a 9" rim? Do you see a true 1" in projection from the 8" to 9"? Keep in mind I'm keeping my current tires that are on the stock rims. They are new. Thanks for the feedback.

SILVERADOSC540 Senior Enthusiast

SILVERADOSC540

Posted
Posted

Should pick up 1.09 inches. .59 inches for the offset difference and 1/2 inch for the wheel size difference. The one inch wheel difference will be split inside and outside.

blackout07 Senior Enthusiast

blackout07

Posted
Posted

Should pick up 1.09 inches. .59 inches for the offset difference and 1/2 inch for the wheel size difference. The one inch wheel difference will be split inside and outside.

 

If you look at the two wheels in terms of backspacing, the 9" wide Monsters (+18 offset) will provide roughly 5.7" of backspacing. The 8" wide stockers (+31) also provide roughly 5.7" of backspacing. The difference is essentially half an inch both ways.

 

 

Backspacing is much easier to comprehend IMO than offset, and will allow for easier comparisons between wheels of different widths.

 

I use the following formula to convert:

 

TO CONVERT OFFSET TO BACKSPACING:

 

For positive offset wheels: (Wheel Width +1)/2 + (offset * .03937)

 

For negative offset wheels: (Wheel Width +1)/2 - (offset * .03937)

 

TO CONVERT BACKSPACING TO OFFSET:

 

Backspacing – (Wheel Width + 1)/2 * 25.4 = offset

 

Round this result to the nearest milimeter. If the answer is a negative number the wheel has negative offset, if positive then a positive offset.

 

And for your reference:

 

Factory backspacing:

17x7.5= +31mm offset(5.5" bs)

18x8= +31mm offset(5.7" bs)

20x8.5= +31mm offset(5.9" bs)

SILVERADOSC540 Senior Enthusiast

SILVERADOSC540

Posted
Posted

Well shiver me timbers. I guess that I was way off, but in the end the number is about right. If the backspacing is the same on both and the XD's are an inch wider, than the inch would be to the outside. So, while I completely pulled my original answer out of my a$$ and wasn't even close to correct on my calculations, as it turns out I was off by 9 100ths of an inch. I think. Maybe. I'm not sure. Now I have a headache. Damn it Matt.

MTPoleKat Enthusiast

MTPoleKat

Posted
Posted

Just a question? I've never understood the tires sticking out past the fenders. Is it just a look thing? Why would you want to throw mud and rocks all over you pick-up?

 

I would like a 17" x 7.5 aftermarket rim with 5.5" backspace (same as stock) but I can't seem to find anything. I can drive down a mud road and not get mud thrown all over the place with my factory rims. My old pickup I put a set of rims on and when I drove mud I had mud on the hood and everywhere because the tires stuck out. Not knocking anybody your pickup do what you like just have never understood it.

 

I like tall skinny tires 235 245 max width only way you can keep control on the muddy gumbo in my country.

SLong Enthusiast

SLong

Posted
  • Author
Posted

Thanks for all the feedback. So, what is the verdict as far as how far the 18x9 +18 monsters will stick out compared to the 18x8 +31 stock wheels? Was the 1.09" an accurate estimate?

 

One more question since you guys know a lot more than me. They also have the monsters in 18x9, in either a +33 or +35. Can't remember exactly. Pretty much factory offset, just the rim width is 1 inch wider than the stocks. How far will that will stick out from where the stocks currently sit? Just 1/2" further out or a full 1"? Thanks for all the help.

cparks555 Senior Enthusiast

cparks555

Posted
Posted

Just a question? I've never understood the tires sticking out past the fenders. Is it just a look thing? Why would you want to throw mud and rocks all over you pick-up?

 

I would like a 17" x 7.5 aftermarket rim with 5.5" backspace (same as stock) but I can't seem to find anything. I can drive down a mud road and not get mud thrown all over the place with my factory rims. My old pickup I put a set of rims on and when I drove mud I had mud on the hood and everywhere because the tires stuck out. Not knocking anybody your pickup do what you like just have never understood it.

 

I like tall skinny tires 235 245 max width only way you can keep control on the muddy gumbo in my country.

A lifted truck needs a wider stance or it looks like its going to tip over IMO.

 

Thanks for all the feedback. So, what is the verdict as far as how far the 18x9 +18 monsters will stick out compared to the 18x8 +31 stock wheels? Was the 1.09" an accurate estimate?

 

One more question since you guys know a lot more than me. They also have the monsters in 18x9, in either a +33 or +35. Can't remember exactly. Pretty much factory offset, just the rim width is 1 inch wider than the stocks. How far will that will stick out from where the stocks currently sit? Just 1/2" further out or a full 1"? Thanks for all the help.

The +18 will look the best and give you a wider stance without hanging any tire outside the wheel well.

SLong Enthusiast

SLong

Posted
  • Author
Posted

Raceline wheels offer their Rampages in a +25 offset. Falls right in between the stocks at +31 and the +18 monsters. I'm just leery of the +18 monsters pushing it out too far for my narrower tires and it not looking right. The Raceline rims look pretty much exactly like the monsters. Thoughts?

blackout07 Senior Enthusiast

blackout07

Posted
Posted

Well shiver me timbers. I guess that I was way off, but in the end the number is about right. If the backspacing is the same on both and the XD's are an inch wider, than the inch would be to the outside. So, while I completely pulled my original answer out of my a$$ and wasn't even close to correct on my calculations, as it turns out I was off by 9 100ths of an inch. I think. Maybe. I'm not sure. Now I have a headache. Damn it Matt.

 

I know right? Lol. It does get confusing and I'm not even sure at this point. I guess the extra inch would be all to the outside?

 

 

Just a question? I've never understood the tires sticking out past the fenders. Is it just a look thing? Why would you want to throw mud and rocks all over you pick-up?.

Because it looks so damn good, and what cparks said. Lifted trucks shouldn't look like they're on wagon wheels.

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