NastyZ28.com - Camaro High Performance Chassis Tuning
I believe there is a steering knuckle that's been tufftrided and allows for the use of the Corvette disc and caliper... I'm looking for the part number of it.
General spring guidelines. Now is a good time to look at my Z28 spring information. See what was available stock, and go from there. UNDER NO CIRCUMSTANCES should the spring and/or shock be allowed to bottom out. This can cause immediate loss of control.
As a general rule or GUIDELINE:
Springs: 500 to 600 #/inch front & 200 - 250 #/inch rear
Swaybar: 7/8" to 1" front & 7/8" rear swaybar.
works well as a starting point.
For high load cornering try:
Springs: 750 #/inch front & 300 #/inch rear
Swaybar: 7/8" front & 1" rear swaybar
Also see how to tune a suspension via swaybars and springs below.
2nd gen tires and wheels? I know some folx put 17" wheels on their 2nd gen. I've used the standard 15 x 7" wheels with 245 60x15 tires. I like the car to be balanced on all 4 corners. With an obscenely large tire on the front of the car you run the risk of interference with the steering.
Trimming or removing the bump stops can increase the amount of suspension travel above production limits. You can use bump stops on the shocks to prevent the suspension from bottoming out.
Replace your stock wheel studs with heavy duty wheel studs. I saw a guy lose a $45,000 race car due to wheel stud failure.
Alignment and suspension geometry
Initial front suspension geometry:
Camber: 2-3.5 degrees negative
Caster: 2-3 degrees positive
Toe: 1/16 - 1/8 toe out.
The chassis should be set up to allow for equal weight on both front wheels and both rear wheels while the driver (or a couple sacks of concrete) are in the drivers seat. Weight bias can be adjusted via different length spring shackles or by shimming or trimming the front springs. Measure and make any adjustments with the swaybars disconnected. Upon reconnecting the swaybars make sure they do not preload the chassis.
Chassis Setup & Tuning (Drag Racing)
Slicks and performance street tires operate at generally higher pressures. Start with 18 - 20 pounds, and adjust up or down by 2 - 3 pounds at a time.
By optimizing starting line technique, you can substantially alter 60 foot times which will cut ET
Work with available traction and establish a baseline before tuning.
Experiment with shift points and launch technique until you have two consecutive runs within .05 seconds.
Car needs to launch straight and steer straight during gear changes.
Manipulate Weight transfer, when car wheel stands or squats
ET, super street, super gas doesn't need to be light weight. this will cost in durability and consistency. The benefit of a light car is it allows you to add weight where you want it.
Moving ballast is a significant tuning device.
A 4 link allows for extra tunability, but is complex, a ladder bar setup is suitable for high nines. Ladder bars with a stick causes violent launches and produces more roll rotation during gear changes.
Shock absorbers are critical, they allow for chassis reaction no matter what type of suspension is in use.
Shock Tuning (adjustable styles)
Front: 90/10 setting provides maximum weight transfer and traction.
Rear: 50/50 is for slick conditions, allowing the body to separate from the chassis and plant the tires. When track conditions are ideal, 70/30 will take some bite out of car.
Shocks are the best tuning device. Results of a shock change can be confirmed by other tuning changes.
Example: if your car goes quicker when you lighten the rear shock, the tires can take a harder hit, you can confirm this by taking out air in quarter pound increments to reduce the amount of support to the sidewalls.
If you keep taking adjustment out of the rear shocks, and the car keeps picking up, you'll run out of adjustment. Keep playing with tire pressure, ballast and launch RPM. Either add a lower gear to multiply the torque or raise the ladder bar, this will hit the tires harder. Remember though, to return air to your tires, lower the launch RPM to your baseline and stiffen the shocks so that you've made one change.
Car stiffness is important. Car will react better to tuning changes with a stiff chassis due to flexing caused by the reaction of the suspension. All four corners of the car must be braced and the engine and transmission should be secure within the car. This will allow you to tune the car with the shock absorbers and find out what needs to be done with the rest of the car.
To control pitch rotation at the front of the car, adjust shocks, adjust the amount of suspension travel, or add/remove ballast. At the rear you can raise or lower the ladder bar, move the instant center of car, or add/remove ballast.
When you launch so hard, the rims hit the ground and throw the rear end back up, you need to remove hook from the car. To remove hook, you need to stiffen the rebound adjustment so that the rearend doesn't separate from the car so fast. With each stiffer setting the 60 foot times pick up and the car improves its reaction time. A bit more air in the tires, moving ballast forward, or lowering launch RPM would help also. Lower the ladder bar as a final adjustment. Rebound affects how the tires will get hit, bump relates to how the tires will react.
Next move to the front tires. If the car likes stiffer rebound, it will like less front travel to pull the tires out of the lights. If you limit travel to much, the car will dart when it hits bumps. You have to be the worlds best authority on how your car behaves. Use knowledgeable advise and experimentation with the laws of cause and effect.
Tires, Gear Ratios, Shocks & Traction
Suspension/Chassis tuning & Troubleshooting
Performance Handling (Road Racing)
SUSPENSION THEORY BASICS - by
When you get used to taking corners much, much faster than you ever thought possible in your car, with absolutely no perceivable body sway, tire squeal, or loss of control, you will find it difficult to drive a car with lower handling capabilities - it gets addictive! The right setup will give you this capability. Some weight & weight distribution, suspension, and handling basics before we get into details of modifications:
1.) Minimize overall vehicle weight as much as possible. With no other changes, the lower a car's weight, the less weight transfer there is in a corner, and the more cornering force a car will generate. A related issue is front/rear weight distribution - the closer to a 50%/50% distribution this is, the easier it will be to set up the car for maximum cornering. The handling will also be more balanced, predictable, and controllable. One easy way to help distribute weight more evenly is to relocate the battery to the trunk area. There are kits available to do this from a number of suppliers. Be sure you use the best quality, heaviest gauge battery cable possible to avoid increasing electrical resistance and be sure the battery is well-anchored.
2.) Minimize suspension unsprung weight for best handling. Unsprung weight is what is on the outboard end of the suspension - what is not being "sprung" by the suspension. This includes wheels, tires, brake components (rotors, calipers, drums) suspension arms, spindle, rear axle and associated brake components, and the leaf springs. By reducing unsprung weight you are reducing mass in motion in the suspension. Less weight moving up and down means the suspension can react more quickly to changing road surfaces and keep the tires planted on the ground better. This all equals higher acceleration traction, cornering traction, and overall better handling and road feel.
3.) Choosing spring rates, other suspension components. Generally, there are two "schools of thought" in setting up a car suspension for cornering / handling.
Both of the above have some (+) and (-) . The soft spring/stiff anti-sway bar setup, with matched shock absorbers, is, in my opinion, probably the best for an all-around (race and street) car as it gives you a very flat cornering car with a liveable ride on the street. Either approach will require a high performance shock absorber matched to the spring rates you are using. I ended up using the advice of some other SCCA members with 2nd generation camaros and generally went with the Guldstrand Engineering recommended spring rates, anti-sway bars, and shock absorbers on my car. The stiff spring/soft anti-sway bar approach also gives you a flat cornering car but I would recommend this more for a car that will see little if any street use as the ride is extremely harsh and best suited for the smooth surface of a race track. Cars I have seen set up this way have used 700 + lbs/in front springs, 190 to 200 + lbs/in rear springs, a 1" to 1 1/4" fr. anti-sway bar, and often a small or no rear anti-sway bar.
For those who have not heard of either Dick Guldstrand or Herb Adams, both of these have been involved with GM F bodies for many years. Dick Guldstrand has been involved with car racing (dirt track, oval track, road racing) and race car building since the late 50's. His area of specialty is GM car suspension, including the F body (camaro). He has an engineering degree and has also worked in the aerospace industry. His Guldstrand Engineering website is www.guldstrand.com - good source of parts/technical info for F body suspension and related hi-perf modifications. Also reachable at 11924 W. Jefferson Blvd., Culver City CA 90230 (310) 391-7108. Herb Adams is an engineer who also has many years of experience with GM cars, racing, and particularly the F body. He worked at GM early on with the Pontiac Trans-Am project (suspension in particular). I couldn't find a web site for his company, his high-performance auto parts business is: Herb Adams VSE, Monterey, CA 93940, (831) 649-8423.
Balancing handling by adjusting front vs. rear roll stiffness (This applies to the dynamics of really any front engine, rear wheel drive car. I have little experience with front wheel drive cars and hope to never see the day of a front wheel drive camaro!): Note: with the specs of the setup I describe further below (springs, anti-sway bars, shock absorbers, suspension alignment, etc) I ended up with very flat cornering and neutral handling car which needed little adjustment of front vs. rear roll stiffness. Varying tire pressure and changing front anti-sway bar bushing material is about the only change I have had to do to "dial-in" the suspension for different track conditions and for street use.
TIP: Before you do anything else, try adjusting front vs. rear tire pressure. This is easily done and you would be surprised at what a difference a 2 to 5 PSI change can make. Try adjusting in 2 PSI increments, and record the pressures that work (cold pressures, for repeatability) so you can duplicate them again in the future at different tracks, etc. - be aware that differing air temperature will have an effect on pressures.
The ideal end state is a neutral handling car which neither understeers or oversteers in a constant turn at a constant speed. A well set up car can be pushed into oversteer by more throttle, and back toward understeer by backing off the throttle - you can "steer" a well-balanced car by the throttle alone.
1.) If you car understeers too much (the front of the car wants to "push" out of the turn and it takes excess steering effort to keep it in the turn, you have too much front roll stiffness, and possibly the wrong tire pressure (too low). You need to reduce this front roll stiffness. What is happening is that the front tires are not able to maintain enough traction and are pushing (really sliding) out of the turn. The technical term for this lack of cornering traction is "slip angle". The more a tire loses cornering traction, the higher a "slip angle" it is said to have. In this case, the front tires have a higher slip angle than the rear tires. This causes the nose of the car to slide out of the turn and is commonly called "understeer". You are most likely not aware this is happening because there is not enough "slip" to feel, nor enough tire squeal to hear. If you have a good set of high-performance tires, and do not need to upgrade them, follow the advice below to balance handling (assuming all the other suspension parts are installed and chassis work is done). If not, I would recommend you invest in good tires before you do any further suspension tuning. Tires are the only point of contact where all the hard earned $ you invested in suspension and other hardware actually meet the road. Good high-performance will make the single biggest difference in overall car handling and especially cornering (see tire section for tire/wheel size/type recommendations). To adjust the suspension and reduce understeer:
a.) You can reduce front roll stiffness and adjust tire pressure by:
- increasing front tire pressure (for street use do not go above the maximum recommended safe pressure-usually posted on sidewall, ask tire manufacturer if you do not know what this is). By increasing tire pressure you are allowing the tire to work as intended, and the full tread width to stay firmly planted on the road for maximum cornering traction. Too low a tire pressure will cause the sidewall of the tire to deform, causing traction loss and understeer. At the extreme opposite end, excessively high tire pressure can distort (bow) the tire tread, causing only a small portion of the center of the tread to contact the road. This too can result in loss of traction and produce understeer.
- substituting softer anti-sway bar bushings (as discussed in the anti-sway bar part of the suspension section )
- reducing anti-sway bar stiffness - easier if you have an adjustable anti sway bar, but otherwise you will have to install a thinner bar.
- reducing front spring rate - install softer springs.
b.) If you feel the front setup is just about correct, or the above changes are not enough, or you want to experiment with changes and their effect on overall handling, you can also increase rear roll stiffness and adjust tire pressure by doing the opposite of the above to the rear suspension: - decreasing tire pressure (I wouldn't go below about 25 psi for a high-performance street radial or you will really speed up tire wear - ask the tire manufacturer for recommendations on min. safe tire pressure) - installing harder anti-sway bar bushing materials (see discussion under anti-sway bar section) - increasing anti-sway bar stiffness - increasing spring stiffness - can be done of course by swapping in stiffer springs, but you can also add an additional "helper" leaf. A number of auto parts suppliers carry these, to include J.C. Whitney, and they usually give specific info on how much these increase spring rate. This is a relatively easy modification and could provide you that extra measure of rear spring stiffness you need without spending a whole lot more time or money on your "project car".
Other suspension considerations in balancing handling and cornering:
- another consideration is the tire size, the tread width particularly. If you have smaller tires up front, your front tire/wheel combination may be too narrow, and you are losing traction in a turn, causing understeer. Consider going to a wider (and even a lower profile) tire. You may have to change to a wider wheel too, matched to the tire tread width. A good rule of is to select a wheel that is as close as possible to the tire's tread width-the width of the contact patch that touches the ground (don't confuse this with section width). The tire manufacturer can get you all these specs. This will allow the tire sidewall to remain vertical to allow the full width of the tread's contact patch to touch the road.
2.) If you car oversteers too much (the front of the car wants to steer into the turn too much, you have too much rear roll stiffness.and may also need to adjust tire pressure What is happening here is that the rear tires have a higher "slip angle" than the front tires, causing the tail of the car to slide out of the turn and aim the nose too much into the turn. Try increasing rear tire press / reducing front tire pressure, or some combination, and adjust roll stiffness as detailed below:
a.) To decrease rear roll stiffness: - installing softer anti-sway bar bushing materials (see discussion under anti-sway bar part of suspension section) - decrease anti-sway bar stiffness - decrease spring stiffness
b.) You can also increase front roll stiffness to further correct oversteer by: - substituting harder anti-sway bar bushings (as discussed in the anti-sway bar section ) - increasing front anti-sway bar stiffness (install new anti-sway bar) - increasing front spring rate - install stiffer springs.
Handling - Objectives
Handling comes down to one thing: Traction, and not just traction during cornering.A good handling car will be predictable and easy to control under cornering, braking, acceleration, on all sorts of roads, and in all sorts of conditions. As with anything,
this means you need to compromise or balance the chassis for the majority of conditions the car will be operated under.....
Street vs. Racing - Ride vs. comfort.
Understeer vs. Oversteer
Most cars are designed to understeer, which is when the car approaches a corner it wants to keep going straight. If you enter a turn too fast the front end will slide and turning the steering wheel is useless, so you'll have to slow down and turn into the slide. This is also known as "push".
Oversteer is the opposite, where the rear end wants to slide out from under the car while the car continues to turn into the curve. This is known as "Loose".
Most cars are designed to understeer so a normal driver can instinctively control the car. In a race situation, oversteer is prefered because a good driver can control the car easier and corner faster.
To reduce understeer you add oversteer to the car by:
Summary: You want to set the car up to oversteer. I repeat this because if you run out and spend $$$$ on a larger front swaybar, you're actually adding more understeer to the car, which you are (supposed to be) trying to get rid of.
Wheels and Tires
The only thing attaching your car to the road surface is the tire. Therefore, the tires are the key to a good handling chassis. A poor driver with good tires can outrun a good driver with poor tires anyday.
Again, compromise is necessary due to the conditions the car will be driven under.
Shocks dampen the actions of the springs.
For the ultimate in tunability, you want adjustable shocks. These are expensive and if you don't know what you're doing, a waste of money. Since you're reading this they may be beneficial. Street shocks are designed to provide most of the dampening force on the rebound, i.e. when the tire is going back down towards the road after it hits a bump. This makes for a smooth ride. Performance shocks usually dampen at a 50/50 rate, rebound vs. compression. This improves handling at the cost of a firmer ride. Nitrogen gas shocks are the prefered way to go. Adjustable shocks allow you to tune for compression or rebound, depending on the road conditions.
Swaybars and Springs
Swaybars or stabilizer bars twist when a car leans during a turn.
If your car doesn't have a rear swaybar, PUT ONE ON. This will be the most significant handling improvement you can make for little money.
By switching to polyurethane, you effectively make your bar think it's 20-25% larger in diameter due to reduced deflection which rubber mounts. This will also speed up the bars reaction time.
Springs hold the car up. They'll also rattle your teeth if they're too stiff. Use swaybars to TUNE your ride while maintaining softer springs if you need to drive on the road. Shortening springs lowers the car, which lowers the center of gravity. If you go too far, your car will bottom out either on the road or on the suspension, so pay attention.
Weight distribution - balance. Less weight = less effort to accelerate/decellerate.
Alignment & steering (deflection, scrubbing off speed).
Chassis reaction time/bushings/bracing
You want your car to be fast as hell, but the brakes are an important part of any cars overall handling package. If I can drive deeper into a corner, get on the brakes for a shorter period of time and get back onto the gas quicker than the other guy, I will be faster in the long run. The biggest problem with brakes is HEAT. When brakes overheat they will "fade", where you need to press the brake longer and/or harder to get the car to slow down.
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