okay i just need to know if im thinking clearly the stock rims that i have are the 15x7 5 spoke rims the backspacing is 3.25" so on a 7" rim the outside lip of the rim would be 3.75" from the mounting surface correct? so if you had a rim that was 8" wide with a 4.38" backspace the outside lip would be 3.62" from the mounting surface right??

a 7"rim will measure about 8" total width, not seven, so you measurement would be 4.75 from the mounting surface to the outside.

What are you getting at? if you have a 15x8" wheel, it would actually measure about 9" wide. If it has 4.5" of backspacing it will fit fine. a little less is will sit a hair more inboard, a hair more it will sit a bit outboard.

explain to me why a 7 inch rim measures 8 inches total width, and also why if the total width is an inch bigger then why the distance between the mounting surface and the outside is 1 inch more and not half an inch?

why does a 7" rim measure 8"? it just does, all wheels measure about 1" wider, and a bit taller, than the given size. I think the width is the distance between the sidewall beads that set into the wheel

Backspacing is the measurement from the back of the hub on the wheel to the inside bead. It doesnt care how you measure the width.

gotcha. so the if theres 2 beads outside and in, the overall width increases 1" so theres a .5" increase on both sides, so a 3.75" distance from mounting surface to outside lip would only increase .5" so it would be 4.25"


thanks for trying

i think you are getting confused.

forget this extra 1/2" thing for a bit

if you want to know what the backspacing of the wheel is, just measure from the mounting surface, back of the hub on the wheel, to the outermost part of the rim. You dont need to add, subtract, divide anything. Just put a flat-edge across the inside edge of the wheel and measure back to the hub.

Then if you want to determine how much of the wheel fill extend from the hub towards the outside of the car, just do this

ex. you have a 15x7" wheel. you backspacing is 3.5". so you have 3.5" form the mounting surface of the wheels hub to the innermost part of the wheel.

then you have about 4.5" from the mounting surface to the outside of the wheel, this is where you would consider that extra inch.

are we still a little lost or are we getting somewhere?

ok, maybe it would help if i explained what im trying to do

i have a 4th gen rear end (lt1 length) and i want to run ZQ8 16x8 rims but i dont want them to stick out too far. the stock rims should be about perfect but im trying to figure out if the ZQ8 rims will stick out farther than the stock rims that have a 4.38" backspace. i just dont want them sticking out past the fender

anyone know if the zq8 rims stick out farther than the stock 15" wheels?

they are going to stick out of the wells a bit, im almost positive