First Gen Camaros and even Second Gen are sprung very soft. The spring is 327 lbs per inch, it is pushing roughly in the middle of the lower A frame so the wheel has leverage over it. So at the wheel you get only about 116 lbs per inch spring rate. If you want a cushy ride, you go soft like this. Also, the stock Camaro didn't have very sticky or large tires and traction was not high for acceleration or braking.
The E70 series "wide oval" tire was just beginning to be offered on new cars in 1967, by 1969 the 60 series was offered on the Mach I Mustang only. These tires were capable of maybe .7 traction coefficient. So, with a good suspension setup you could corner at .7 G's. The 1967 tires would have a lower traction coefficient. Under full acceleration, braking , and cornering, the tires limit the amount of front to rear weight transfer that can be generated. And the amount of front end roll, lift or dive is created by those forces, and resisted or limited by the springs. In a nutshell, more grip= more spring rate needed, or else more front roll, lift/dive will be generated.
So, when you add more traction, brakes, and power, you will cause more suspension travel when driving at the limit. With stock springs, you will be closer to bottoming out the suspension under braking, and under acceleration, topping out the suspension. You will experience more travel and spend more time at the limits of travel. To keep the car within the design limits, you would need stiffer springs. If you want to improve the handling, you need to control the motion of the chassis closer to normal ride height and stay away from the extremes. When you limit roll, the tires stay in better contact with the pavement and traction is increased, improving conering grip and control.
If the car is lowered you are biasing the suspension toward bottoming out or scraping the headers more easily. You are reducing available travel in bump, and the only way to prevent it is is to use a stiffer spring. For high performance handling, I see front spring rates of 600 to 700 used in the street suspension kits. For crusing around with less sticky or narrower tires, and about 300 to 400 hp, a rate of 500 to 550 is very nice since those cars cannot generate the acceleration, braking, or cornering forces that require a stiffer spring.
The stock Z/28 spring is 380 lbs and the minimum rate to consider. Moog does not list this spring in their catalog for the Camaro but I have crossed it over to a #6308. This would be nice in a restored Camaro with mild mods. Or if you have a bit more power but just cruse, and are not interested in carving corners all the time. Oddly enough, this spring is listed in the MOOG catalog as a replacement spring for a 6 cyl and some V8 Camaros with air conditioning.
Springs don't loose rate with age, they loose height, they will bend or sag with age.
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721LB 6082 *** |
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stock/resto |
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SB street cruse stock tires- good ride |
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SB HD street with wide tires heavy cornering more horsepower, good ride |
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SB HD street and autocross, track use. firm ride. |
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SB road course, or autocross stiff ride |
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Rear spring rate |
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BB - use same chart but could easily go up one step in rate. Guldstrand sells two BB front springs, one for street, one for race. |
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*** 6082 spring: 721lb / inch rate without cutting, free ht 13.330" loaded ht 10", load lbs 2404.
This is my best guess at spring rates sutable for a Camaro for best handling. These figures are just off the top of my head, not really calculated by a computer model or anything like that. What I'm thinking of when doing this chart is all around ride, handling, and acceleration performance on the street, Autocross, and Road course. I don't have a clue as to how this would work on a drag strip.
I'm not in favor of any bolt-on traction devices on the rear springs. With the proper rear spring, you should not need anything else, and SHOULD have better off the line performance than with them.
In general, more tire traction equals more available "G" forces. More G forces requires a stiffer spring.
A stiffer front spring should be matched to a stiffer rear spring.
I've heard reports back that the #6308 will lower a SB Camaro
about 1" The ride is very good, just slightly stiffer than stock. It's
one of my favorite springs for a street Camaro you want as a
cruse-around car and with good sized sway bars, the car can corner
well. These springs work well on a car with less than supercar tires.
If you have 8" wide rims and BFG Radial TA's then the tires can't
generate enough G force to cause problems.
I plan on adding more rear spring info at a later time, but in
short, - A proper leaf spring for handling would be de-arched (flatter)
and
higher rate than stock from #175 to #300+ in rate. It would be
stiffer in the front half of the spring, to control wheel hop. Stock
type multi leaf springs are not bad in this respect, but not as good
as the aftermarket rear springs. I like the Hotchkis rear leaf spring,
it has a thick lower leaf that acts like a built-in traction bar with
no binding.
The Hotchkis hollow front bar is 1 1/8" in diameter by .200" wall.
&endash; 900 lbs/in
&endash; 310 lbs/in
&endash; 380 lbs/in
&endash; 490 lbs/in
Given that information, I've figured the bar rates and resulting wheel rates in lbs, and weight of each bar.
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Diameter |
#at bar |
#at wheel |
calculated weight of bar - lbs |
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11/16 stock |
144 |
109 |
5.6 |
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7/8 |
377 |
285 |
9.2 |
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1" solid, common aftermarket size |
643 |
487 |
12 |
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1.125 |
900 |
681 |
6.2 (hollow) |
1. The rear roll center of the Camaro leaf spring design is inherently much higher than the front suspension, which is below ground level. This transfers cornering forces at the rear at a much higher rate compared to the front. The closer the roll center height is to the center of mass (at that end of the car) the more the cornering forces are transfered directly. (not through the springs or swaybars) to the tire tread.
This is why the old sprint cars with cross spring suspension didn't need swaybars. The roll center is about 1 1/2" below the center of mass, or mass centroid axis on those cars.
The disadvantage of the sprint cars high roll center is, if the cornering weight transfers automatically thru the high roll center. There is nothing the springs or shocks can do to absorb bumps and keep the tires from breaking loose (cornering). The car will act like there is a HUGE sway bar on it but the springs and shocks will not see those loads.
2. When a Camaro leans, it is twisting the stock leaf bushings. This adds a small amount of resistance to roll. If the bushings are solid aluminum, the leaf is going to be loaded in twist much more severely.
You can see this all adds up to higher roll resistance at the rear than you might normally think.
Later 80's Camaros had bigger swaybars on the rear but they have coil spring rear suspensions.
I am NOT saying you don't need a rear sway bar. If you
stiffen the front much at all over stock, you will cause the car to understeer
and have to add a rear bar. Also adding wider rear tires will procuce understeer.
If the Guldstrand mod is done it raises the front roll center and adds both traction & geometric stiffness to the front suspension. This combination may require addition of a rear bar.
The raised front roll center transfers weight when cornering
similar to what the suspension does, but is independent of the
suspension.
Notice that on most rear bar kits, the arms are fairly long and the diamiter is usually small. The rear bar winds up making a small difference, if that difference balances an understeering car, fine. If not, it's not needed.
Guldstrand does not recommend adding inkage to the rear suspension, a rear swaybar or other stuff like panhard bars, or watts linkage. He feels it will wind up hurting rear traction on corner exit. I agree, except I have not been able to balance oversteer/understeer without using a rear anti-roll bar. I've seen cars with their suspension binding because of incompatable suspension "Add Ons" - usuualy traction bars. Make shure you aren't fixing a problem you didn't have in the first place. The best solution is a properly made leaf spring.
Wider and stickier tires on the rear of the car will increase the need for a rear sway bar.
More weight on the rear, or less weight on the front will increase the need for a rear sway bar.
Small block 325 lb. Big Block 327 lb!
Z/28 379 lbs
Rear is somewhere around 125-150
Spring rate is very closely tied to horsepower, traction, car weight, and center of gravity height.
Use springs that will keep the car under control under acceleration and braking.
Use sway bars to make the car corner nearly level, and balance handling - IE oversteer - understeer.
Depending on front end weight, tire size, desired ride quality. 500 -550 would be good for crusing on a lowered Camaro. 600 to 650 for serious autocross with wide tires or big block.
The stiffest small block front spring from the factory is the 69 Z/28 #3932771 OR 3955720, with EK code on the tag, at 379 lbs per inch. Moog part number 6308. Note - Moog does not list this spring in their replacement listings, the replacement spring is #6312 which is a 337 lb spring. I came up with the Z-28 number by crossing over a factory part number from a Z/28 spring to the moog replacement spring for that number.
#6308 has the ends a little shorter than a standard spring and will work fine, the ends will just be a little short of filling the spring pocket top and bottom. I'd try positioning it to fill the lower spring pocket and let the top sit where it may.
Looking down from the top of the spring, a stock spring would have the lower end of the coil at the 12 O'clock position in the lower A frame. The upper end would be at the 10 O'clock position. With #6308, the upper end would be closer to the 12 O'clock position. I have been told the ride height may be a half inch lower than before. I have no personal experience wtih these springs, just talked to people on the web about them.
The 6308 is shown in the Moog catalog for a 1969 Camaro with 6 cyl engnine - Heavy Duty, no air. Don't let this put you off, this spring is fifty lbs higher rate than stock. This rate is NOT for a heavy car, or for VERY wide or sticky tires. It will lower a small block camaro nicely, usually to where the old sagging springs sat.
#6320 would also be a good choice for a heavier SB Camaro, or for a little higher ride height. It has a half inch taller free height and 380 lbs rate. Or, cut it to lower ride height and get a little stiffer rate, maybe 400 lbs if you cut a little off it.
The springs above will give a slight improvement in handling with no or very slight increase in ride stiffness.
I strongly suggest using an aftermarket front spring for High Performance handling or use on a lowered Camaro. Rates in the 550 range for street use, 600 and up for autocross, super street, track, etc.
The Moog #6041 spring is between 600 and 700 lbs depending on how much you trim it to fit your car. It starts out at 501 lbs per inch with a height of 17.09".
It works for racing or a stiffly set up street Camaro with a lot of rubber and power.
Lowering your car will reduce available suspension travel and the car will either bottom out easier, or will scrape the headers easier than it did before. Also you may have trouble with the tires hitting the fenders. This is where a stiffer sprng is needed or you won't see any benefit in handling from lowering the car. Your Camaro cannot handle well if it is bottoming out on the bump stops. MANY PEOPLE LOWER THEIR CAMAROS TOO MUCH. The cars wind up hitting the bump stops in the corners, and that breaks the tire loose. The suspension can also bottom out under braking, causing the front wheels to lock.
If your stock multi leaf is OK use it. It would be better if it were around 175/250 lbs per inch. as power and traction goes up the need for a stiffer rear spring appears. Any custom spring should have the front half stiffer to control wheel hop. This is especially important on 67's, as they don't have staggered shocks.
I've heard enough bad reports to recomend against the fiberglass rear springs, I've heard of them breaking. The lower the power, the better those springs look.
I like the Hotchkis hollow 1 1/8" front bar, because it's lighter the spring rate is the same as a 1" solid bar. Second choice is the 1" solid bar. If you have heavy duty front springs this size bar is all you need.
Any bar, even the stock one can increase it's EFFECTIVE STIFFNESS by using solid frame mounts or at least the urethane mounts and end links. But using solid aluminum mounts on a 1" bar may be too stiff.
I have KONI shocks now. Take a look at the Bilstein shocks, I've heard good things about them.
Moog/Federal Mogul (have the same part numbers).
Ride Tech, Hotchkis, Guldstrand, Eibach, sell Camaro specific coil springs. Ride Tech also sells coil over coils made by Hyperco which is a very high quality spring, they are what I use.
Guldstrand is kinda racey in their rates and approach I
think they have rear leaf springs, but they might have bronze bushings for
race only use. They did in the 70's when I last used them.
Guldstrand likes stiffer spring rates, with less sway bar.
Hotchkis is similar to Guldstrand, and has good rubber/ polly bushed rear springs to match the front springs. They have a nice hollow front bar for less weight.
Hellwig sells high quality sway bars. Generally they are stiffer
than most for Camaro applications. I think they do that because they
tune for only adding sway bars, not springs.
Hyperco, sells great racing springs for "Street Stock" racing, with one end tapered like a Camaro, the other end flat for an adjuster of the "Hidden" type. They are only about 9" tall and must be used with a spacer.
Carrera and HAL have coil over front shock assemblies for sale.