I keep reading that the stock 18x7.5" wheel has a BS of 5.5".
Yet I've also read that some people say the offset is 40mm.......a few others are claiming that it is 44mm?

When I plug these #'s into the calculator.... http://www.rimsntires.com/specs.jsp

to come up with a stock backspace of 5.5" I need to use an offset of 32mm.

40mm or 44mm equates to a backspace of 5.8" to 6.0".

My questions is does anybody know for sure?
If it's a backspace of 5.5", it sure as heck can't be a 40 or 44mm offset?

 

Are you asking this just for personal knowledge or are you applying it in some way?
If you're asking just to ask, just go with 5.5" of backspace and let it be. A few mm is not something to get all worked up about. As long as you know the backspacing, you'll be fine.

 

trying to figure out exactly how far my wheels will stick out......compared to stock!

 

If you post the rim size and backspacing/offset we can help you and tell you exactly how much farther the wheel will stick out compared to your stock wheel.

 

Assuming POSITIVE Offset!
A 7.5" wide wheel with zero offset means the hub face is 3.75" from either side of the flange where the bead seats (2 X 3.75 = 7.5). Figure the lip is near 1/4" thick, so call it 4" from back face of wheel.

Offset of 40 mm means the hub face is 40 mm from the zero point. 40 mm is about 1.57" (1 inch = 25.4 mm, so 40 devided by 25.4 is 1.57). 1.57 plus that 3.75 is very nearly 5.32" from the wheel flange where the tire bead seats.

Offset of 44 mm means the hub face is 44 mm from the zero point. 44 mm is about 1.73" (1 inch = 25.4 mm, so 44 devided by 25.4 is 1.73). 1.73 plus that 3.75 is very nearly 5.5" from the wheel flange where the tire bead seats.

4mm difference may be the difference between the measuring from rear outside lip versus calculating from inside the rim flange?

32mm devided by 25.4 is 1.25", added to that 3.75 is 5 inches back space.

If NEGATIVE offset, meaning the hub face is closer to the back of the wheel ..... subtract the offset from that 3.75".

Look here .... but understand that when a wheel is said to be 7.5" wide, that's INSIDE the rim flage to INSIDE the rim flange as the tire sees it. When measuring from outside rim flange you'll see 1/2" or more greater measurement. They often draw diagrams showing to outside cause "they do".

https://www.rsracing.com/tech-wheel.html

 

Hey GA4x4sxrew, I have a 2004 f150 supercrew and I just bought 33x12.50x18 and also fuel offroad hostage rims with +1mm offset with 5.5 backspace. Will these tires fit Good without rubbing?and how far will they stick out? Thanks!

 

I'm getting ready to swap out my factory 18" XLT rims with the factory 275/65-18 tires, for some **** Cepek Gunmetal 7 rims in 17x9. Backspace is 5.0" and offset is 0. Going to add BFG AT's in 305/65-17. This will all be with a Rancho Quicklift and replacement 3" blocks in the rear to maintain rake.

Thoughts?

 

I ran some 17x9 American Racing wheels with a 0 degree offst on my '04 Lariat...they will stick out 2 inches more then the stockers. Tires in the pic are 295x70x17's (33.5x12) no rubbing even doing some offroading.





Here's what the 295x70x17's looked like.








I had the 295x70x17 Toyo MT's on my '04 Lariat. They were on 17x9 with 0 degree offset American Racing Craters. 33.5x12 and fit perfect on these wheels.

I think your wheels and tires will look good Todd!

 

Thanks PawPaw! Your rig is looking pretty nice too!

 

I know this in an old thread, but I am looking for a little insight. I am looking at a set of wheels 17x8.5 with an offset of 18 mm and a backspace of 5.45". How much will they stick out beyond the stock wheels? Incase you need the tire size, im looking at 285 70 17. Thanks!