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Backspacing is the distance from the inside lip of the
wheel to the surface that bolts up to the axle. See
Backspacing Illustration
We offer custom backspacing on all of our
steel wheels. There is no extra charge.
"Standard" Backspacing is (in most cases) the
smallest backspacing that can be built without reversing
the shell. It is also the backspacing that has been
calculated as the best average of brake clearance and steering
geometry for factory straight axle applications.
High impact will build wheels with custom
backspacing for no extra charge, within the limitations of
what can physically be built, as well as remaining within good
engineering and load carrying parameters. This column gives
the range that can be built without "reversing
the wheels shell". In some cases it is
possible to achieve even lower backspacing by "reversing
the wheel shell" There are several issues which should be
considered when ordering any backspacing other than
"Standard" backspacing
Caution: Reduced backspacing
increases the load on bearings, ball joints and steering
components. It also causes the front tires to swing in a
larger arc, resulting clearance problems with the fenders at
full steering lock. Please be advised when ordering wheels
with reduced backspacing. Custom wheels are non-returnable
Caution: Deeper than Standard
Backspacing may cause clearance issues with brakes, tie
rods, knuckle and other components. Make sure you understand
the issues described below and have thought this through
before you order such wheels. Custom wheels are
non-returnable. We are of course happy to go over any of
these factors with you, however the final decision is always
yours.
Standard backspacing usually gives the
smallest backspacing that is possible to build without
reversing the wheel shell.
By reversing the wheel shell, we can achieve lower
backspacing, thereby spacing the tires farther away from the
vehicle.
If you look at a wheel, you will see that one side
has a deeper “bell” than the other (The bell is the large
diameter opening where the brakes fit in. The center of the
wheel welds into the “valley”, a reduced diameter portion
of the wheel). The “valley” is offset toward one side of
the shell. Normally, we build our wheels with the large bell
toward the inside. “Standard backspacing” places the
center as far inboard as is possible to weld into the wheel
with the large bell to the inside. It is possible to reverse
the wheel shell and put the small bell toward the inside. If
we reverse the wheel shell, it becomes practical to hit
backspacing between 2 and 2.5 inches. See
Reversed Shell Illustration
With the small bell on the inside, from going deeper than
2.5 inches begins to put the brakes inside the valley of the
wheel. The valley of the wheel necks down to about 12.6”
inside diameter. Thus, if the brakes have a larger diameter
than 12.5 inches (with 15 inch wheels. 17s have much more
room) they will not fit inside the valley.
See
Brake Clearance Illustration
Reduced backspacing increases the load on bearings,
ball joints and steering components. It also causes the front
tires to swing in a larger arc, resulting clearance problems
with the fenders at full steering lock. Please be advised when
ordering wheels with reduced backspacing. Custom wheels are
non-returnable items.
The best way to space tires out farther away is through the
use of longer axles. In some cases, since custom axles are
considerably more expensive than custom wheels, a compromise
solution is attempted by decreasing the backspacing of the
wheels. Since this will move the tire farther out from the
vehicle, some tire clearance can be gained. While this is 100%
true in a non steering axle, on any axle that steers, it
has a compromise effect. Since the pivot point (Kingpin or
ball joint axis) is not moved out, instead the wheel and tire
are moved farther out from this steering pivot point, when the
wheel is turned the wheel and tire describe a larger arc. If
we estimate full steering lock to have the wheel tire turned
45 degrees from straight, this will have swung the tire back
in toward the spring or radius arm. Suffice to say that if we
reduce the backspacing 1 inch, at full lock we will have
gained about 1/2" clearance from the radius arm or leaf
spring, but we will have had the tire swing forward into the
fender or back into the rocker panel an additional inch.
Because the wheel is getting wider, it begins to have too
much leverage at the outside. This added leverage has too much
risk of damaged steering components, ball joint, spindle and
even the wheel center to be safe. We do not build reverse
shell wheels in sizes larger than 10" wide.
This pulls the wheels in closer to the
vehicle, desirable with wider than standard width axles. It is
no problem to build wheels with a deeper backspacing, however
brake clearance must be considered when attempting this with
15" wheels. The inner “Bell” (The bell is the large
diameter opening where the brakes fit in. The center of the
wheel welds into the “valley”, a reduced diameter portion
of the wheel) of the wheel is just under 15” inside
diameter. This begins to narrow down 3.5” from the
rear lip of the wheel, and at 4.25” from the rear lip of the
wheel, is down to 12.6” inside dia. (With the wheel shell
reversed, the inside diameter is down to 12.6: at about
2.5" BS) Standard backspacing will keep the brakes in the
large clearance portion of the wheel. When going deeper, it is
necessary to determine how far in the wheel the brakes will
enter at the backspacing desired. Then it must be determined
if the brakes will fit inside the inside diameter of the wheel
at this depth.
See
Brake Clearance Illustration
Additional
Data: Fitting 15" Beadlocks on 8 lug (3/4 or 1Ton) axles
Backspacing can be made deeper than
standard until you run out of "valley" going the
other direction. These limits are specified on the
catalog pages. As the wheel gets wider, so does the valley,
and thus so does the possible backspacing.
Custom wheels are non-returnable items.
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