Think I found my wheels

[4wVoy]

after a lot of searching trying to find a wheel that gave my eyes a hard on that had a decent offset and back spacing for a decent amount of money, I think i got one. Problem is they aren't stocked up quite yet but in the next week or so they will be. They are Ultra Wheels Bolt. I will be running 17X8 with +25mm offset. The other few wheels I saw were around the 0 offset or worse. Plan on wrapping them with some General Grabber AT 2's 265/70/17. She is gonna be a purdy little thing when I'm done Just thought I would share my new find in case someone else was looking for a nice black wheel.

Here they are

[djthumper]

Are you sure it is a +25 that you want? That gives you a deeper backspace IIRC

[Mudwheelin]

They look great man!

[4wVoy]

backspace will be 5.48", trying to keep most of the tire inside the fender wells, that should put me about 3" sticking out if my math is correct running markmc's spacer. I could be wrong since all this backspace, offset math is kinda new to me

[navigator]

I read through these backspace threads and am never really sure if I can figure it out....
Best I can tell
an 8 inch rim with ~5.5 backspace gives 2.5 sticking out or 1.5 inch more than stock.
If you add 25MM (~1 inch) for offset and 1.5 inch for a spacer that would be about 4 inches more than stock.
Some of the guys smarter than me can let me know if my math is right.

[4wVoy]

i read somewhere, might have been roadie that said something along the lines of stock offset is 50mm ~2", new offset is 25mm ~1", difference is 1", stock rim is 7" wide, new rim is 8" wide, .5" inside and .5 inches outside wider, that gives us ~1.5" and then add in the 1.5" spacer and that gives you 3". That is how I came up with 3"

I could have jacked that all up lol but it seems like most are running 15-25mm offset

[Trail X]

I think backspacing is easier to understand so I'll work from there.

Stock backspacing is 6". It's a 7" rim, so the equivalent is approximately +60mm offset (for reference).

Your proposed +25mm rim is essentially 5" backspacing. It's also an inch wider. So with no wheel spacer, your outside rim would stick out 2" further, with a 1.5" spacer, you'd have your outside rim edge 3.5" further out from a stock rim.

[navigator]

I'm 1/2 inch off in my calculations. Is that because I didn't consider the thickness of the rim to be about 1/2 inch?

[Trail X]

Not sure, I had trouble following your post.

+25mm = +1in off centerline. Centerline is 4" from the back lip on a 8" rim, so the backspacing of the proposed rim is 5" (4"+1").

Stock rims have 6" backspacing. So that right there means the inside rim will be 1" out further than stock.

Add in the rim width, 7" vs 8"... so that's an extra inch for the outside rim (with no wheel spacer).

Then add in the wheel spacer thickness. 1" (due to BS) + 1" (due to rim width) + 1.5" (wheel spacer) = 3.5"

[navigator]

I was thinking he said backspace was 5.48 or 5.5 for easy math.
5.5 from the back of the rim leaves 2.5 to the front of the rim. (5.5+2.5 = 8).
5.5 backspacing would mean (in my simple mind) 2.5 front spacing(sticking out).
2.5 + 1 (offset) + 1.5(spacer) gave me 5 inches front spacing total.

the stock rim being 7 inches wide with 6inches of backspace give me 1 inch of front spacing.
5(new rim)-1(stock rim) = 4

[4wVoy]

wouldnt it only be .5" due to the 1" wider wheel, split the difference from center point, i know the wheels are 5.48" back spacing rounding up to 5.5 according to http://www.rimsntires.com/specs.jsp
Center line isnt always at the 4" mark on a 8" wheel from what I am told, they made it confusing doing all this.

My head is starting to hurt haha, it will be a waiting game to see how they look once they are mounted. what i do know is going with a +25 from 0 offset, i will be an extra inch inside the fender wells

[navigator]

James knows this stuff, I'm sure he has it pegged. I was trying to back into it logically but that isn't always possible for me to do

[4wVoy]

this is the post i was referencing earlier and how i came up with the numbers i did. This is from the roadie on GMTN

I usually do the math myself like this:

OEM offset 50mm, new offset 18mm. Change is 32 mm outward = 1.25"
OEM rim width 7", new rim width 9". Change is 1" outward (half of the rim pushes outwards, half pushes inwards.
Spacers = 1.5"

Total = 3.75" outward

It'll work, but because of the arc that the edge of the tire will sweep out, you'll be cutting the back of your bumper and possibly rubbing at the back edge of the wheel well where the rocker panel mounting bracket is, when you go to the 265s.

And as I mentioned, I don't think the 245mm wide tires will be rated to fit on a 9" rim.

[Trail X]

Looks like there are a few ways to do it. I honestly hate offset because I think it's a fairly useless metric unless you're the engineer doing the rotational moment calcs on the wheel hub bearing. Backspacing seems to make much more sense to me, because it doesn't use a theoretical centerline. Yeah, the rim edge does play into things too, but it's normally only a 1/4" or so I thought.

Chris, I think you were right assuming the 5.48 backspacing that was posted before, I didn't see it!

[navigator]

thanks JD, glad to know my math is right even though it seems more complicated than the article Josh posted. I don't think Josh's article takes into consideration backspacing unless Roadie just converted backspacing to offset.

[Trail X]

You can do it either by offset or backspacing. I just personally trust backspacing measurements more.

When you're converting between backspacing and offset, you can potentially run into complications (such as rim thickness and "offset centerlines").

[navigator]

DANG! I mis-understood the term offset and I have read dozens of posts on it.
So offset is the distance from the center line to the mounting surface.
If you have an 8 inch wide rim with 4 inches backspace you have essentiall 0 offset.
If you have an 8 inch rim with 6 inches of backspace you have essentially 2 inches (50.8mm) offset.

I was thinking offset was the little space you see highlighted by "B" in this image.
It is hard to explain but I thought it was the difference between the backspacing and the mounting surface due to the mounting surface tapering in or out. I was thinking you needed to know the offset in addition to backspacing.

man this really clears it up for me.

if I have it right now we could plug this formula into a web page to make it easy to figure the amount the new rim will stick out. Iknow this brings up high school algebra that we haven't used in like 20 years but stay with me.

sw= spacer width
nw = new rim width
nb = new rim bs
ow = old rim
ob = old rim bs
x= amount new rim sticks out vs old rim
x = sw+ ((nw-nb)-(ow-ob))
lets pretend we are looking at a new rim 8 inches wide and 4 inches of BS
x = 1.5 + ((8-4)-(7-6))
x = 1.5 + (4-1)
x = 1.5 + 3
x = 4.5

did I do it right?

[Trail X]

Looks right. Another way to think about it is this:

x = sw+ (ob-nb) + (nw-ow)

Oh - and we are working on a calculator... it's just been a while in development.

[onelow1ton]

Here are some good calculators both with visual aids I like the first one best becuse you can set one as what you have now to what you want to go to

http://www.rimsntires.com/specs.jsp

http://www.1010tires.com/WheelOffsetCalculator.asp

[4wVoy]

rimsntires one schooled me up decent, used that for a few different options for wheels