62 Impala Street Challenge Question?

[Durg]

What is ride height (or reference height of the component) front and rear for the shockwaves and bags, also ballpark PSI for the front and rear? Thanks, Kevin.

[darren@ridetech.com]

It is difficult to actually measure the front Shockwaves, so I just measure front the fender lip to ground. First measure fully compressed and fully extended, to ensure you have at least 5" of wheel travel. Ride height should be just over mid travel, about 3/5 the way up. For example, on my Chevelle I have about 21.25" fully compressed and 26.25" fully extended. I drive it at around 24.25". I would start with about 6 clicks in the rebound (right knob) and about 2 in the compression. You could stiffen it up a little for better handling.

Same with the rear. The rear air spring is easy enough to measure if you want to do that instead. Needs to be about 5" tall at ride height. Give or take a 1/2". About 3 clicks in the rebound and 1 in compression.

[Durg]

Any idea at what psi. you get your ride heights at ? The Impala is probably 400 pounds heavier too I would imagine. When you measure the rear bags, do you include the upper and lower metal pieces or ONLY the rubber element. I can lay the crossmember on the cement floor with no headers on. With headers, they hit about 3/4" before the front crossmember. I have 2" dropped spindles on too. With the crossmember on the floor, the lower a-frame still has travel but I don't know yet if the shockwave is bottoming or not. These dimensions will help me determine that.If I need to stiffen the front too much to get my desired ride height, I guess the dropped spindles will have to go?

[darren@ridetech.com]

It's gonna be between 100-115 psi depending on engine weight. The rear bag measurements should include the 1/2" thick end plates.

[darren@ridetech.com]

We normally use a stock height spindle on this car. Drop spindle puts it too low. The tires will normally hit the inner fender wells before the crossmember hit the ground. Fully inflated, how high is the cm off the ground?

[darren@ridetech.com]

Drive up on a 2x4, then deflate it and see if the cm still hits the ground.

[Durg]

I pulled the headers off and tried again tonight. The front crossmember actually has 3/16" clearance from the floor when the a-arm contacts the frame. I guess the frame contacts the lower a-arms before the shockwave bottoms.I can only get about 90 psi in the shockwaves right now because my regulator is bound up. 90 psi raised the frame about 4-1/2" up. (This is without fenders radiator inner wells etc. installed)When you talk about the shockwaves " fully " inflated or fully raised, about how many psi is that? I am afraid that with the dropped spindles 2 negative things will occur and I am guessing these are at least a couple reasons why you don't use them. 1. Too much air pressure has to be put in the shockwave to attain a reasonable driving ride height. 2. At ride height, the upper a-arms are very flat which would hurt camber gain when the suspension goes through it's travel. Also I have not even begun to figure out where the height of the roll center is on these cars.

[britt@ridetech.com]

Durg,

I would not rely on "approximate pressure values" to set up the car. Air pressure is not directly relational to suspension travel.
Take this example: You have two cars that are identical except one has a small block and one has a big block. Both require the same ride height (air spring at 5" installed). But due to the heavier big block the air pressures will be significantly different between the two (possibly 85psi for the small block and 100psi for the big block). The important part, which is a key benefit to air springs, is that the spring rate increases with increased air pressure while remaining at the same installed height. So the small block car needs a lower pressure, and thereby a lower spring rate to hold the vehicle at ride height. The heavier big block car needs a higher spring rate, so it requires more air to achieve this rate.

The only way to properly set up any air sprung vehicle is to raise the car to achieve the air springs installed height, regardless of air pressure. If it's 65psi, GREAT; if it's 105psi, GREAT; so long as the air spring is 5".

[Durg]

I am somewhat confused because you could have a conventionally sprung vehicle at the same ride height with a 500 pound spring or a 1500 pound spring. The ride and handling characteristics will be extremely different. Why isn't this the same with air? An Impala going into a corner with 40 pounds of air in the rear bags at 5" height will be less likely to oversteer than one going into a corner with 80 pounds of air in the bags. A stiffer right rear spring whether air or coil will make the car loose on entry. I know this can be compensated for with front spring rate, sway bar diameter, and other things such as rear roll center height etc. etc. I just don't understand how it does not matter what psi you run. I figured these systems are sized according to vehicle weight and suspension geometry etc. so there would be a recomended psi to run and it would get the optimum ride height close.

[darren@ridetech.com]

The suspension should bottom out on the Shockwave. The control arm should not hit the frame. Can you take a picture of this?

It will take about 130-140psi to fully inflate the car.

[britt@ridetech.com]

Durg,

You are correct in the fact that you can have TWO steel springs with different spring rates and the same installed height. However, you need two springs to accomplish this.

Air springs are a bit different than steel springs. They have the ability to have a very soft spring rate at the installed height, but when compressed will progressively increase in a hurry. This gives us a plush ride while still maintaining performance.

With our system we have engineered which Shockwave to use to provide the optimum spring rate at the installed height for good ride quality. However, unlike a conventional steel spring we have a bit of "room" to work with; which is why we can use the same Shockwave in both a small block and big block application.
Though the air spring is the same, the increase in air pressure raises the spring rate to what is required for the big block vehicle. The increase is not so great as to upset the handling of the vehicle.
In addition, a double convoluted air spring is VERY progressive by design. So the more the car leans, the more the air spring compresses, and the more spring rate is supplied. This is different than a normal steel spring in the fact that as the car rolls to one side the spring rate quickly matches what is required by the vehicle to keep it flat. (take a look at any picture of our 66 Chevelle going through a corner, it is very flat.)

[Durg]

I'll try to post one tonight. The right front lower is contacting the frame and the left front is close but not touching. Thanks.

[Durg]

Makes sense to me now. I am used to using springs with a linear rate and these would be progressive. Thanks.

[Durg]

O.K. here is the photo of the lower control arm contacting the frame. Today the L.F. is contacting and the R.F. has about 1/8" clearance. Last night it was just the opposite. Front crossmember is at the floor now. I don't need the piece of frame that is hitting as I believe it was for the stock lower a-arm bumper to hit against. I don't really want to remove it in case it ever was put back to stock.

http://i224.photobucket.com/albums/dd252/kdurgin/Impala8-20-08004.jpg

http://i224.photobucket.com/albums/dd252/kdurgin/Impala8-20-08005.jpg

http://i224.photobucket.com/albums/dd252/kdurgin/Impala8-20-08006.jpg

What should I check next? Thanks, Durg.

[darren@ridetech.com]

I looked at a couple photos of our 62 chassis and our 61 display chassis. Looks to be handing down a bit farther on your chassis. Manufacturing tolerance were pretty large back then. Maybe a few smacks with a BFH???

[Durg]

As long as you guys don't think there is an issue, I can deal with the bumper tabs. I will proably grind the welds and remove them and store for possible reinstallation. Thanks.

[Durg]

I ground off the bump stop tabs, so they will no longer be an issue.

http://i224.photobucket.com/albums/dd252/kdurgin/Impala8-23-08004.jpg