4th
Generation (1993 - Present)
Q: What are the specs on the stock sway bars and springs?
A: 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).
Q: Should I buy weld-on or bolt-on subframe connectors (SFC's)?
A: It is the general consensus that weld-on subframes are the way to go. Bolt-on SFC's have the tendency to loosen with time. SFC's reinforce the unibody. This is especially important on F-Body's with T-Top's, or convertibles. The convertibles have SFC's installed from the factory.
Q: What are the factory front end alignment specs?
A: The settings are:
Caster |
+3 degrees |
+/- .5 degree |
Camber |
+1 degree |
+/- .5 degree |
Toe in |
.15 degree |
+/- .5 degree |
Q: What are some suggested front end alignment specs?
A: Based on some list member recommendations:
Recommendations: |
Caster |
Camber |
Toe |
||
(deg) |
(deg) |
(in) |
|||
L |
R |
L |
R |
|
|
Stock suspension |
+3.5 |
+3.5 |
-.5 |
-.5 |
0 |
Eibach springs |
+4 |
+4 |
-.8 |
-.8 |
0 |
Q: What's that hollow clunking noise from the rear over bumps?
A: 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.
Q: What are the dimensions of the 16 inch wheels?
A: 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.
Q: What tire options are available?
A: 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.
Q: How should I rotate my tires?
A: 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.
Q: How come my GSC tires are showing such excessive wear?
A: 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.
Q: Is it normal for the rear tires to be rubbing against the wheel well?
A: 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.
Q: What is the maximum backspacing I can use?
A: Front - 7" Rear - 7 3/8"
Q: What is the widest tire I can use?
A: 275x17s will 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 when using the 50mm offset ZR-1 wheel, but not excessively. If you are going to use 17x11 wheels, the 36mm offset Corvette GS wheel is a better choice. If you have a stock panhard rod, it's likely they will rub in inner wheel well under hard and uneven cornering. An adjustable panhard rod will precisely locate the rear end, centered from side to side, to minimize the risk of rubbing the inner fender.
Q: What are some common GM wheel part numbers?
A:
|
Wheel: |
Part # |
Offset: |
Backspace: |
Weight: |
|
17x9.5 ZR1 front wheels (silver finish) |
12512905 |
50mm |
7.07" |
19lbs |
|
Corvette GS ZR1 style 17x9.5 |
12361447 |
50mm |
7.07" |
17lbs |
|
Corvette GS ZR1 style 17x11 |
12361446 |
36mm |
7.25" |
21lbs |
|
Corvette GS Centercap |
9592388 |
|
|
|
|
Center Cap w/F-1 Logo |
12364006 |
|
|
|
|
Center Cap w/Pontiac V-Crest Logo |
12364007 |
|
|
|
|
Center Cap w/Chevy Bow Tie Logo |
12364008 |
|
|
|
|
Center Cap w/GM Performance Parts Logo |
12364009 |
|
|
|
|
Externally threaded lug nuts |
10194314 |
|
|
|
|
Lug nut covers (silver plastic) |
12337914 |
|
|
|
|
Externally threaded locking lug nut set |
999057 |
|
|
|
Q: How can I get another locking lug nut key?
A: 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 suggestible to order an extra key just in case you lose the original.
Q: Why are 1993 front brake pads different from the 1994 and up models?
A: 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.
Q: What are the best replacement brake pads to use?
A: GM probably makes 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 short of the Winston Cup pads. For those, you'll have to talk to Dale Earnhardt.
Q: Why does my steering wheel vibrate when braking the car at high speeds?
A: Chances are your front rotors are warped. This is a very common problem on the F-bodies, especially the 1998s. Many people have had their rotors replaced under warranty, and some people have been able to get this fixed, some have resorted to putting on aftermarket "slotted" rotors.
Some tips you can follow to avoid warping your rotors:
Q: What's that metal squealing noise from the rear on high speed turns?
A: 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.
Q: What can I do to make my rear brakes stop squealing?
A: Although the front brakes on the LS1s often have a problem with the rotors warping, the rear brakes have another problem with a painfully loud squeal. This doesn't appear to be a problem with the rotors, but the backing of the brake pads themselves. When your car is new, there is a thin padding between the back of the brake pads and the inside of the caliper. Due to the need of the brakes to move and flex a little, after a while, the caliper wears away this padding, and is now making direct contact with the brake pads, thus creating the annoying noise. There's really nothing anyone can do about the flex of the brakes, however you can put some sort of anti-squeak on the back of the brake pads and this will help, but only for a while. Apart from a complete new rear brake design, there doesn't appear to be a permanent solution for this.
Q: Can I bleed ABS brakes without a problem?
A: 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.
Q: What types of higher performance brake fluid are available?
A: 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 |
Q: Why does my parking brake handle come up all the way sometimes, is it broken?
A: This is actually by design. The handle will do this in order to get the center console off. If you push the button in on the handle when pulling it up, and if you pull really hard this can happen. Don't worry, you are not causing any damage to the car, just push the handle back all the way down, and pull it back up a little slower, and you should be fine.