Ok guys..I've searched and searched and I am more confused now than ever. I figured if we could get a real clear and concise explenation in one thread of how the offset, backspacing and wheel width all effect each other and how a certain size will look on our trucks, it would really help out a lot of us. I know the stock 18's are 7.5" wide and have a 5.5" backspacing. The wheels I'm looking at are 20x9 with +35 offset and 86.9 center bore. I want to put Nitto TG 305/55-20's on these rims. Will this work without my truck looking like a big roller skate? I don't want my wheels to stick out from the wheel well at all, if possible.

So if anyone out there has a way to explain all this to me and others, i'm sure it would be greatly appreciated by all. Or maybe its just me..I am a little slow at times

Thanks guys


BREW

 

OK brew- the deal:

20x9 with 35mm offset.

to get the backspacing:
9/2=4.5" add between .5 to 1.0" to account for the front and back rim lip. so
4.5" + .75" = 5.25"

+35mm = 1.377 inches

5.25" + 1.377" = Roughly 6.5 inches of backspacing.

The Higher the backspacing, the more tuck you will have. The lower the backspacing, the wider you'll get... so you will stick in roughly one inch more than your stock wheels


Justin

 

Here's a link that shows the info your looking for

http://www.wheelsforless.com/offset_diagram.asp

Basically, Backspacing is measured from the outside rear lip of the wheel to the inside mounting surface(part of wheel that contacts your brake rotor).
Offset is measured from the center of the wheel to the mounting surface.Where the confusion comes in is that wheel width is measured from the inside of the beads NOT the overall width of the wheel so your 9 inch wheel probably has an overall width of 10 inches with 9 inches between the beads.

The less backspacing the more the wheel sticks out of the wheelwell.

I have 2006 factory 20's and they are 20x8.5 with a +44 offset,backspace is about 6.5 inches.

So using the wheels that you are looking at compared to factory,your width between the beads is an extra half inch overall(1/4inch from centerline) but you offset is less(+35 compared to +44).

The math for factory:+44=1.73 so 1.73+4.25(half width between beads)=5.982 +.5 for distance from outside lip to inside bead=6.482 backspace(6.5).

Your wheels:+35=1.377 so 1.377+4.5(half width between beads)=5.877 + .5 for distance from outside lip to inside bead=6.377 backspace(6 3/8).

Assuming the same distance from ouside lip to inside bead(about 1/2 inch),your backspacing should be about 6 3/8 whereas factory 20's are 6.5.

Your wheels will only stick out about 1/8 inch more than factory 20's.

Hope this helps



balogUK,
I agree with you.
you answered while I was typing my long winded explanation.

To avoid confusing this anymore, I compared what he wanted to my factory 20's.

Using my calculations(assuming 1/2 lip)I get 6 3/8 backspace compared to 5.5 for the 18's.
So yes ,about 1 inch more inboard but also about 1/2 inch more outward because wheel width increased by 1.5 inches(7.5 compared to 9).

 

NOW THATS WHAT I'M TALKING ABOUT!


you guys rock



So one more question...with the wheels I want with the Nittos and a 2" level kit, do you think I will have any rubbing issues?


BREW


RP....make this a sticky..please

 

brew- you should be good- the 305/55R20 TG's are 12.6" wide when all is said and done, 1" in, .5" out because of overall width increase and an overall height of 33" you're golden.

 

SWEET

Now I just gotta see if my bank account will allow it this month


BREW