Wheels, Tires And Wheel Alignment; Wheels; Tires; Wheel Alignment - Fiat Project X1/9 Complete Manual

chassis box members to support the bottom of the hoops.
Refer to the pictures.
Cut a slot in the under side of the targa roof panel to
insert the main hoop. Cut through two layers of sheet
metal, being careful not to damage the top outer skin. An
abrasive disc in a pneumatic die grinder works well for
cutting sheet metal.
The main hoop can be welded in place as soon as it is
properly fitted. Note that the bottom of the hoop is po-
sitioned foward of the door posts to allow easy access
behind the hoop for welding to the base pads. The main
hoop can be welded to the door post structure at the top
of the doors and to the lower skin of the targa roof section
in several spots to increase the stiffness and strength of
the combined structure. Do not weld the front hoop in
place at this time.
Cut and fit the foward braces between the front strut
towers and the front hoop. These fit through the front
side air duct holes. After these are fitted, they, and the
front hoop, can be welded in place.
Cut and fit the diagonal for the main hoop. Note that
this passes through the cockpit rear panel and intersects
the left lower chassis box member inside the original fuel
tank bay. Sandwich a steel plate between the diagonal base
and the box member to spread out the loads.
Cut and fit the remaining roll cage braces. It is recom-
mended that the remaining braces in the cockpit section
not be welded in place until the cockpit interior has been
completed, because they make access to the cockpit more
difficult. Note that a transverse tube is installed between
the front strut towers. This is not part of the safety roll
cage and can be made of lighter material such as 1-112 inch
square tubing with a .06 inch wall. Its function is to stif-
fen the front strut towers and mount the fuel cell. The
roll cage parts are contained in PBS Kit Number 17.
WHEELS, TIRES AND WHEEL ALIGNMENT
Wheels
The F-production X1/9 is allowed to use 6-1 /2 inch wide,
13 inch diameter wheels. We recommend the Cromodora
Daytona-style magnesium wheels in this size. These wheels
have conical steel inserts to accept tapered lug nuts for
centering on a 4 inch bolt pattern. Most other brands of
aftermarket wheels are made to accept straight shouldered
lug nuts which typically don't provide very accurate cen-
tering, especially in a racing application where the wheels
are removed and replaced frequently and the mounting
holes become worn. The G car can use 6 inch x 13 inch
wheels. These are available from Cromodora with a 98mm
bolt pattern.
For racing, the wheel lug bolts should be replaced
with studs and nuts. This can be accomplished by drilling
the wheel mounting flanges, brake discs and spacers to
112 inch. Drill the new pattern to a 4 inch bolt circle
(not the stock 98mm) if Cromodora 6-112 x 13 wheels
are to be used. Then 112 inch bolts can be inserted from
the back side and the heads can be tack welded to the
back of the axle. Some grinding is required on the bolt
heads so the brake disc will clear the outer edge. It is
recommended that the flange be mounted to a wheel
when welding the studs into the flange. This will assure
correct alignment after welding. In order to drill the axle
flanges, they must be removed from the wheel bearings.
In general, it is suggested that the wheel bearings be re-
placed with new ones when the axle assemblies are reas-
sembled. Use matching tapered lug nuts with the 112 inch
bolts to retain the wheel securely. PBS Kit Number 15
can be used.
The Cromodora 6-112 x 13 wheels have a "0" offset.
A 112 inch positive offset would be about optimum on the
X1/9. Therefore, a 112 inch thick aluminum spacer should
be added behind each wheel. This is in addition to the
stock steel spacer on the rear of the X1/9. On the front
of the F-production car, a steel spacer is included under
the Lancia brake discs, so no additional spacers should be
added outside the discs except for the 112 inch aluminum
one.
Tires
Tire technology changes so rapidly that no firm recom-
mendations can be made, because in the next six months
they would be obsolete. The chassis modifications des-
cribed are intended for tires in the range of 20 to 21
inches in diameter. Clearance to the front springs is quite
limited so the front tires cannot be excessively wide or
they will interfere. More room is available at the rear so
the rear tires can be wider than the front tires if desired.
Wheel Alignment
The optimum wheel alignment will vary somewhat de-
pending on the tires, but a few general guidelines are
appropriate.
The front caster is not readily adjustable on the stock
X1/9. With rod ends on the leading end of the trailing rods
it could be adjusted somewhat by changing the wheelbase,
but this is not a legal modification. The trailing rods
should be adjusted to-be of equal length and to position
the wheels foward and aft in the stock location as closely
as practical. This should give equal caster on each side.
Lowering the car will effectively increase the positive cast-
er somewhat. The increased caster couples into slightly
increased negative camber on the outside wheel when
turning, which is okay. However, this whole effect is prob-
ably negligible for practical purposes.
The adjustable camber plates allow fine tuning of the
camber angles with relative ease. After lowering the car,
it may be found that the camber is so far off that the de-
sired setting is outside or nearly outside the adjustment
range of the camber plates. This problem can be corrected
by slotting one of the bolt holes in the suspension bracket