Terrible Tom <SilverEightynine@aol.com> wrote:
: Kyle Kozubal wrote:
[...]
:> SO...................what size(s) can I fit with a mild tbar crank? The
:> Pro Comp Series 8089 17X8 rims have 4.5" of backspacing.
: 32 tall or 11 wide is about the limit on a stock suspension.
: taller/wider than that and you will see rubbing.
: Personally, and I'm not trying to tell ya what to do with your truck,
: but I think wheels that stick out way the hell past the fenders, look
: really bad. I have 31x10.5x15 Kumho mudders on Chrstine, the wheels are
: backspaced about 3 to 3.5 inches outwards. I've never really been
: thrilled with it, but even with a 3 inch body lift, it was what I had to
: do to keep from having tire rub.
: http://members.aol.com/silvereightynine/front.jpg
: Thats a fairly good photo that shows how far out the wheels sit from the
: fenders. I think if you went 4.5 inches outwards back space... its
: going to stick out too far and look.... different.
I don't mean to nitpick :-) but just wanted to throw in here
with a comment about backspacing. Backspacing is the distance
from the back (inner) side of the rim to the back (inner side)
of the mounting surface, which is what rests against the wheel hub.
As such, you won't have negative backspacing or outwards backspacing.
To determine wether a particular backspacing moves a wheel in or
out as compared to a wheel which has the mounting flange in the
very center of the rim, you need to know the width of the rim.
An 8" rim with 4" of back space has the flange in the middle of
the wheel. The wheels that Kyle is looking at which are 8" wide
with 4.5" of backspace would mean that the mounting flange is 1/2"
outboard of the middle of the rim. So, 4.5" of backspacing on an
8" rim is actually sucking the wheel "in" towards the truck 1/2",
not pushing it 4.5" out. (Note that 4.5" of backspacing on a 10"
wide rim *would* be pushing the wheel out by 1/2"). That's why
you can't determine wether the wheel is being pushed in or out
by the backspacing number alone; you need to know how wide the
rim is.
Another term that sort've gets thrown into the mix and
confused with backspacing is offset. Offset measures the
position of the mounting flange in relation to the center
of the wheel, and can be positive or negative. Basically,
a wheel with the mounting flange in the exact center has no
(or zero) offset. Move that flange outboard 1/2" like with
Kyle's rims, and that rim would be said to have 1/2" positive
offset. A mounting flange which is inboard of the center of
the rim is said to have negative offset. A "deep dish" wheel
has negative offset. Negative offset pushes the rims out, away
from the vehicle, and positive offset sucks them in, towards
the vehicle. So, when you say that Christine's wheels are
backspaced 3 to 3.5 inches outwards, they actually have 3 to
3.5 inches of negative offset, as opposed to backspacing. If
your rims were 8" wide, that would mean that your backspacing
would be 1" to 1/2". (Which seems extreme, I think maybe what
you meant is that the tires stick 3-3.5" out from the fenders?)
Offset and backspacing are just two different ways of
expressing where the mounting flange sits. Offset tells you
the distance from the center of the wheel to the flange and
backspacing tells you the distance from the inboard edge of
the rim to the flange. You need to know the rim width for the
backspacing figure to be useful, but by the same token, although
offset alone tells you wether the mounting flange is inboard or
outboard of center, you probably want to know the rim width there
too since the purpose is to determine wether or not these rims
are going to fit on a particular vehicle, and you need to know
the rim width in order to measure properly and calculate your
tire's section width.
Anyway, sorry for the nitpicking, it certainly isn't my
intent to slap anybody down, :-) its just that wheel terminology
can be pretty cryptic until you get a solid grasp of the concepts,
and I know it took me a while to wrap my brain around it,
especially when you hear all these terms bandied about with everybody
seeming to use them in slightly different ways; it gets messy
quick. :-) I just wanted to throw that info up there so as to
steer anybody who might happen to stumble across this in the right
direction. :-)
--
-Jon-
.- Jon Steiger -- jon@dakota-truck.net or jon@jonsteiger.com -.
| '96 Kolb Firefly, '96 Suzuki Intruder, Miscellaneous Mopars |
`-------------------------------- http://www.jonsteiger.com --'
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