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What are the specs
on the stock sway bars and springs?
What are the factory
front end alignment specs?
What are some suggested front
end alignment specs?
What's that hallow clunking noise
from the rear over bumps?
What are the dimensions of the 16
inch wheels?
What tire options are available?
How should I rotate my tires?
How come my GSC
tires are showing such excessive wear?
Is it normal for the
rear tires to be rubbing against the wheel well?
How much
backspacing is required for the wheels?
What is the widest
tire I can use?
How can I get another locking lug nut
key?
Why are 1993 brake pads different from the 1994 and
up models?
What are the best replacement brake pads to
use?
What's that metal squealing noise from the rear on
high speed turns?
Can I bleed ABS brakes without a
problem?
What types of higher performance brake fluid are
available?
What are the specs on the
stock sway bars and springs?
The V6 models have a 30mm front sway bar and a 17mm
rear sway bar. The spring rates are 223 pounds per inch in the front and 95.4
pounds per inch in the rear.
The regular V8s have a 30mm front sway bar (same as
V-6 model) and a 19mm rear sway bar. The springs are 292 pounds per inch up
front and 114 pounds per inch in the rear. The 1LE and WS6 suspension package
has a 32mm front sway bar and 19mm rear sway bar (note, 1993 and early 1994
1LEs got a 21 mm rear bar). The springs are 360 pounds per inch up front and
130-180 pounds per inch (progressive) in the rear (note, 1993 1LEs got the same
springs as regular V8s).
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What are the factory
front end alignment specs?
The settings are:
Caster +3 degrees +/- .5 degree
Camber +1 degree +/- .5 degree
Toe in .15 degree +/- .5 degree
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What are some
suggested front end alignment specs?
Based on some list member recommendations:
Caster Camber Toe Total
(deg) (deg) (in)
L R L R
Stock suspension +3.5 +3.5 -.5 -.5 0
Eibach springs +4 +4 -.8 -.8 0
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What's that hallow
clunking noise from the rear over bumps?
A clunk is most likely the rear springs which are
"popping" over bumps. If you have squeak, it's probably caused by the metal
springs rubbing against their metal perches. In either case, a Technical
Service Bulletin (#B005001) calls for the placement of rubber isolators at the
bottom of the springs to act as cushion. You can probably do this yourself by
wrapping some rubber hose around the bottom coil (down by the axle) of each
spring.
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What are the
dimensions of the 16 inch wheels?
Their size is 16" x 8 ". The offset is 55 mm. Stud
attachment circle diameter is 120.7 mm. Stud size is 5-M12 x 1.5 - 6H THD
metric.
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What tire options are
available?
All Z28s, Formulas, and Trans Ams come with Good Year
Eagle GA (235/55R16) touring tires as stock. Options for Good Year Eagle GS-C
(245/50ZR16) tires (option QLC) or Good Year Eagle RS-A (245/50ZR16) tires
(option QFZ) are also available. With either of these Z-rated tires, the car
gets a the 155 MPH speedometer and does NOT have a speed limiter. This is
because GS-Cs and RS-As are Z-rated for speeds over 165 MPH. In 1993 and 1994,
only the QLC option was available. In 1995, the QFZ option became available,
but it was required for all cars with traction control (ACS). In 1996, QFZ
became the "recommended" tire for traction controlled cars, but QLC could be
ordered.
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How should I rotate my
tires?
Wheels on the 4th gen f-bodies have the same off-sets
on the front as they do on the back. This is unlike some of the 3rd gen cars
which have different front and rear wheel offsets. In this case you have to
remove the tires from the wheels and move the tires to a different wheel (while
keeping the wheels in their respective place). This is not a problem on the 4th
gen since all the wheels are exactly the same. You can rotate from front to
back (usually every 5,000 miles), but if you have Good Year Eagle GS-Cs make
sure you keep the left side on left and the right on the right, since the tires
themselves are directional.
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How come my GSC tires
are showing such excessive wear?
That all depends on your driving habits. Obviously,
the harder you drive (take-offs, cornering, etc.), the more wear and tear
you're going to put on the tires. Be careful though not to gauge the "wear"
based on the outer edge of the tire.
Look at a set of new GSCs carefully. The tread depth
of the grooves is shallower on about the outer 1.5 inches of tread. There is a
very obvious step in the mold at the bottom of the grooves. This is done to
make the tread stiffer at the outer edge to improve performance. But a side
effect is that the outer edge is going to look worn out before the tires are
used up. In fact, they probably have their best performance when that outer 1.5
inches goes bald. This is how Yokahama 008s autocross tires look when they are
new.
You should
definitely replace your GSC tires once you
hit the tread wear indicators on the inner two-thirds of the tire. You might
also want to get an alignment with a negative camber (around -0.5 to -1.0) to
reduce the amount of uneven wearing.
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Is it normal for the
rear tires to be rubbing against the wheel well?
The rear tires on 4th gen f-bodies will rub at the
front of the wheelwell under hard cornering. This is caused primarily by the
body moving laterally, due to the soft rubber in the panhard bar bushings, with
possibly some panhard bar flex as well. It can be lessened by installing poly
bushings or an aftermarket bar (which usually comes with harder bushings).
It is conceivable that there might also be some
deflection in the rear control arms/bushings which contributes to this. But in
any case, the rubbing is cosmetic only, and it shouldn't be damaging the
tires.
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How much backspacing
is required for the wheels?
5 and 3/4 inches.
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What is the widest
tire I can use?
Assuming you've gone to a 17" wheel, 275s should fit
without any problems. You should even be able to get away with 285s. As for
315s, they will stick out from under the wheel well, but not excessively. If
you have a stock panhard rod, it's likely they will rub in inner wheel well
under hard and uneven cornering, possibly resulting in loss of control of the
vehicle. But a stiffer panhard rod and jounce bumper spacers (available from
SLP), you'll be much safer. The spacers ensure the tire won't hit the
outer lip of the fender. If you go to 315, it's suggested to go with at least a
1/4" offset spacer on each rear wheel (available through SLP). Mr. Gasket also
makes wider spacers. Summit carries them in 7/32" and 7/16" sizes (part number
2370 and 2372, respectively) for $20 a pair. You shouldn't need spacers for the
front wheels and it's probably not suggested because of the additional stress
the new angle would put on suspension components.
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How can I get another
locking lug nut key?
When you bought your car, you should have received a
small, double-business- card-sized piece of paper that had the serial number of
the locking lug nut key for your car. Different cars have different keys. Extra
keys can be ordered from Amcor (12955 Inkster, Livonia, MI 48150,
800-831-9604). Their hours are 9AM - 11AM and 1PM - 4PM CST. Keys are $10 each
and can be shipped overnight.
If you lost the serial number, Amcor will not give you
a key. If you're fortunate enough to still have the original key (but no serial
number), then you can send your key to Amcor and they might be able to match it
up. But make sure you take off the locking lug nuts first just in case you have
to remove a tire while Amcor has your key. And, GM does NOT keep a database of
keys to cars. If you loose the key and the serial number, the you're out of
luck. You'll have to have the locking lug nuts cut off with a power hammer.
This will occasionally ruin the lug stud (requiring its replacement), and it
could also damage the wheel. But you really don't have a choice considering you
lost both the key and the serial number.
It's highly suggested that you write down your serial
number in your owners manual or someplace where it won't be lost. It's also
suggested to order an extra key just in case you lose the original.
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Why are 1993 front
brake pads different from the 1994 and up models?
According to the "Parts & Illustrations Manual",
the 1994 front caliper housing for the pads was modified thereby requiring
thinner pads. Aside from the housing, all other parts (the piston, seal, pins,
etc.) are the same. The 1993 housing assembly has part numbers 18018730
(right) and 18018731 (left) with the front brake pads as #12510027. The part
numbers for the 1994 (and up) housings are 18021251 (right) and 18021252 (left)
with the front pads as #12370006. Visually, the 1993 housing is rectangular
(looking perpendicular to the hub axis) while the 1994 (and up) housing is more
trapezoidal. Also note that these part numbers hold true for both the V6 and V8
models, and that there is nothing different about the rear brake assemblies or
pads between these years.
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What are the best
replacement brake pads to use?
GM probably make the best stock replacement pads which
will last the longest and provide adequate stopping power. However, if you're
looking for improved braking ability from pads, your best bet is go with a set
of carbon metallic brake pads. Performance Friction (available through Auto
Zone) makes some of the best sets of these pads:
Pad Type Front part#/cost Rear part#/cost
-------- ---------------- ---------------
Street 6234 / $39.92 4134 / $49.98
Z-rated 623Z / $95.62 413Z / $90.62
90-compound 14.4 / $197.65 13.4 / $128.70
Winston Cup 702F / $300 702R / $300
The Street pads are the basic replacements and provide
marginally better stopping power over the GM pads. The Z-rated pads are
street/strip combo and work excellent with minimal fading and dusting. The
90-compound pads are meant for hard race track driving. They dust a lot, but
provide the best stopping power.
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What's that metal
squealing noise from the rear on high speed turns?
Assuming that you haven't completely run a brake pad
down the metal plate, this noise can come from C-clip axle end play. This moves
the rotor closer and father away from the caliper mount. When the edge of the
rotor touches the caliper mount, you will hear the noise - usually only when
turning in one direction (i.e. rotor moves out enough to hit in only one
direction). The Caliper mount can be relieved in the area that it touches or
the caliper mount can be shimmed. Keep in mind, if this was not a problem, GM
would not have shims. In the 1994 service manual, information on this can be
found under "Brake Caliper Alignment" in section 4B - page 27 (4B-27),
entitled: "Rear axle assembly with rear disc brakes" (figures 1 through 4 and
38). There is however a Technical Service Bulletin (#474201A) for this which
you should advise your GM service person about.
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Can I bleed ABS
brakes without a problem?
Yes, although the preferred method is pressure
bleeding and using the Tech1 service tool. But you can do a manual bleed if you
make sure the ABS system was not active during the last drive. Just start your
car and watch the ABS IN-OP light. If it stays on for 3-4 seconds and goes out,
all is fine for a manual bleed. If the light stays lit for 10 seconds or more,
an error is logged and the Tech 1 tool must scan and clear the code before you
bleed. For manual bleeding, make sure you bleed the system in the proper order.
There are 2 bleeder points on the ABS unit itself that must be bled first. Then
the bleed each brake in order of furthest from the master cylinder. Rear
passenger first, then rear driver, then front passenger, and finally front
driver.
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What types of higher
performance brake fluid are available?
Various ones are available and can be safely used:
Brand Dry boil Wet boil DOT Price/pint
----- -------- -------- --- ----------
Prestone HD ? 284 F 3 $3.00
Ford 550 F 284 F 3 $3.50
PFC Z-rated 550 F 284 F 3 $7.00
Castrol LMA 446 F 311 F 4 $3.00
ATE Super Blue 536 F 382 F 4 $12.00 (1 liter)
Wildwood Hitemp 570 F ? $7.00 (3/4 pint)
AP550 >550 F ? $13.00
AP600 >572 F ? $21.79
Castrol SRF 590 F 518 F $35.50
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