Another Wheel Question

[Aaron Cohn]

I know this kind of question has been asked on a few occasions, Here we go any way. I found a set of wheels I like to put on my 2002 ST. When I spoke to the shop they said they would not fit due to the back spacing he said they were at 0 and mine were a 20-25.

WTF is he telling me and is there an adapter or spacer that I have seen discussed from time to time that work make it so this wheel would work? Oh by the way the wheels are 18x8's. [Broken External Image]:

 

[Dingo]

First of all... Backspacing is measured in inches. I assume he meant offset.

Offset is the distance from the very center of the wheel to the mounting surface. Find out the real specs on the wheel from the manufacturer and we can suggest options, but can't do so without all the info.

 

[Aaron Cohn]

You were absolutely correct. I checked with the manufacture and they gave me this info:



Wheel Size 18x8

Wheel PCD 6x139.7

Off Set +00

Back Side 4.50"



I wish my wifes back side was only a 4.50", but any help would be appreciated!!!:lol:

 

[Travis Munday]

Sadly, you're falling into an easy trap...you should almost always shop for TIRES before wheels. The wheel itself may physically fit within the wheel well, but it's the tires that are the extremities of a wheel/tire package, and typically, it will be the tire that will rub. There are of course a few exceptions, lifted vehicles with poor suspension compression or for stretched tires.



Wheel spacers will do nothing to help you, as that will force the outside of the wheel further away from the vehicle, essentially removing both backspacing and offset (in this case, you could drop to -12mm offset and 4.25" backspacing [with a 4.75 frontspacing] with a 1/4" spacer).



To see if they will fit, remove a wheel from your vehicle, then compress the suspension to about ride height and measure from the mounting surface of the wheel (where the lug studs "start") to the inside edge of the wheelhouse. Compress the suspension and take the same measurement, then turn the steering wheel to lock both directions and repeat the measurement. If at anytime this measurement is less then 5.25" or so inches (depending entirely on tire size here) then the tires will not fit; if at anytime the measurement falls below 4.5", the wheel itself won't work, even without tires.



For the record, figuring out backspacing and offset is pretty simple to do as long as you have wheel width and either backspacing or offset...backspacing and offset are directly related to each other and will always be the same on wheels with the same width.

 

[Dan Long]

If the wheel info you listed above is correct, the problem is the bolt pattern, not the offset or size. Our bolt pattern is 5x114.3 or 5x4.5" (same thing).



As for Tiger's post about shopping for tires first, that's subjective to the goals you have with your trucks appearance and any other modifications you plan on making. It depends on if you plan to keep the factory tire diameter, width, etc... I ran a 18x8 wheel, "0" offset with 265/60-18's (30.5" diameter) at stock height and they fit with plenty of room left. When I lowered it 2", they rubbed occasionally when turning.

 

[Yardsale]

I think what Tiger meant to state is that backspace and offset are related (different ways of measuring the same characteristic) and will be the same on a rim with the same width if either the backspace or offset is the same as another rim of the same width. Two rims of the same width can have different backspacing and offset, but the two are absolutely related.

 

[Travis Munday]

That's correct, Yardsale. For all wheels that are 8" wide with 0mm offset, the backspacing will always be 4.50". For all wheels that are 8" with a 4.50" backspacing, the offset will always be 0mm.



Dan-

The problem with buying wheels first is often you can set your eyes on a particular set, only to find out that when mounted on a chosen set of tires, they won't fit. Typically this isn't an issue when going with a maximum tire sizes (overall height and section with when mounted and pressurized) that are very similar to stock. But when upsizing tires, or going with larger wheels or when starting to mess with wheel widths and offsets, you will rub tires first, not wheels. A wheel/tire combo isn't much good if you can't turn while the suspension is compressed, or turn to full lock.



A good general idea is to shop for wheels AND tires as a package when you start messing with widths and offsets, not really one over the other. Measuring for proper sizing isn't that difficult and can make a huge difference.

 

[Dreman]

I like the rims, though.

 

[Dingo]

Whoa. Hold up.



Wouldn't the backspacing on an 8" wheel with a 0 offset be 4"?



8/2=4.

 

[Travis Munday]

No.



Widths are measured with the bead as the reference point, back and front spacing is measured with the flange as the reference point (outer flange for front, inner for back). A good general rule is an 8" wide wheel is actually 9" wide from very outside to very outside. Same works for diameters. Diameters are measured at the bead, so an 18" diameter wheel will show up as 19" on a tape measure when measured very outside flange to very outside flange.



A wheel with a 4" backspacing and 0mm offset would be listed as a 7" wide wheel.

 

[Dan Long]

I see it as somewhat of a "chicken or the egg" thing... with the knowledge I have of tire sizes, wheel offsets, etc., I can sort of shop for both at the same time in my head. Someone without the understanding that you or I have of them would probably have a more difficult time. It largely comes down to where you're willing to compromise... if I've got my mind set on a certain rim, then I find tires that will fit, and vice versa. I'm also willing to adjust my suspension one way or the other to accomodate the combination.



Like I said though, its will greatly depend on his overall intentions with the truck and if other mods are planned. But, an 18x8 "0" rim will fit with plenty of room for almost any tire reasonably close to stock diameter on a stock suspension ST.

 

[Dingo]

See, I didn't know that. I know wheel sizing, etc., but only in reference to other wheels. If I know what wheel came on a vehicle, I can say if another will work, but I never knew the whole inside of lip thing.

 

[Aaron Cohn]

That is a lot of good info. I appreciate it. One of the last posts from dan indicated that I should not have a problem if I have stock suspension. Stock being the key work here. Mine has a 3" drop front and back!!!!!!! I guess I need to do some measuring and a lot of homework to make sure I am making the right choice here.