1972 Procharged 581 Camaro - Page 14 - Lateral-g Forums

speedjohnston · #**131** 08-12-2010, 03:51 PM

The shop foreman was in as allways today. Ever patient and keeping the riff raff out.

He keeps me company during my many hours of work.

coolwelder62 · #**132** 08-12-2010, 04:03 PM

Look's like he could use a hair cut.Plus tell he is blocking the view of my favorite 2nd.gen.Man I love your car.Awesome stance.Scott

srh3trinity · #**133** 08-12-2010, 08:07 PM

That stance is amazing. This will be one of the best 2nd gens around.

**tones2SS** · #**134** 08-13-2010, 09:30 AM

That's a cool shot!

My dog is the same way. has to be involved with whatever I am doing! lolllll..
That car is NASTY!

Alex396ss · #**135** 08-16-2010, 06:58 AM

Beautiful car!

Alex

Nick.V70 · #**136** 08-16-2010, 06:51 PM

I love the engine set up. Can't wait to see it all together

speedjohnston · #**137** 08-16-2010, 07:30 PM

Thanks guys!

byndbad914 · #**138** 08-17-2010, 06:59 PM

are you going to run the car at that ride height on the front? I ask because it from the shots from the front, it looks like your roll center is below ground. The plane drawn thru the ball joint back to the lower A arm bushings would be pointing upward as you look from center of the car toward the tire.

When I go back a couple pages and look at the front suspension shots with no tires, in nearly full droop, that plane looks roughly parallel to ground - this all may be vantage point issues with the pix, but if that is the case (parallel down around full droop) your roll center requires attention or this car will handle pretty poorly.

Not out to bad mouth, just opening up discussion in case this is something that was overlooked... and out of curiosity, what is the distance from the bottom of the spring pocket to the ground?

speedjohnston · #**139** 08-17-2010, 07:44 PM

Quote:

Originally Posted by byndbad914

are you going to run the car at that ride height on the front? I ask because it from the shots from the front, it looks like your roll center is below ground. The plane drawn thru the ball joint back to the lower A arm bushings would be pointing upward as you look from center of the car toward the tire.

When I go back a couple pages and look at the front suspension shots with no tires, in nearly full droop, that plane looks roughly parallel to ground - this all may be vantage point issues with the pix, but if that is the case (parallel down around full droop) your roll center requires attention or this car will handle pretty poorly.

Not out to bad mouth, just opening up discussion in case this is something that was overlooked... and out of curiosity, what is the distance from the bottom of the spring pocket to the ground?

Must be a vantage point thing. At full droop the outside hangs about 2" below center. The pics were taken when the car was dropped the first time from the jacks with the suspension in the way it is now. Good stance but lower then it will run at (except maybe maxton wich is a straight line). At ride height it is about level.
I haven't played with height a lot yet, just getting everything to clear and sort out all the issues.
The spring pocket is low, only about 2 1/2 inches from the ground the way it sits now.
The springs are 750lb, so it doesn't move around a lot when it is at its ride height.

byndbad914 · #**140** 08-18-2010, 02:01 PM

If you have the lower plane thru the ball joints and inner pivots parallel to ground (not talking anti-dive, etc that will tip the plane, only looking in 2 dimensions from the front of the car) you should be okay. Roughly (by eye) your uppers would be only say 10-15 degrees of angle, which would put the roll center (RC) above ground but maybe around 2", but it also shouldn't move up and down a lot thru motion. Also your upper is short enough v. the lower you should still have camber gain for the first couple of inches of compression, so again, should be fine.

You just really want to be sure that the RC doesn't go from above ground to below ground and back - that is bad for handling. For a straight line none of this matters, but I do assume at some point you may want to go left or right at more than 0.4G

Also, keep in mind that you have spring rate, then there is wheel rate, or what is referred to as motion rate (R). On a strut style car where the spring is directly attached to wheel (in essence), the R is almost at 1:1 which means that for every 1" of wheel motion upward, the spring is compressed 1". You should measure yours to know for sure (super easy, PM if you want details on how to do it), but by eye I would guesstimate your spring's centerline to be roughly half way between the center of the tire contact patch and the lower A arms inner pivot points. So your ratio is 1/2:1 or 0.5.

BUT

when you do the spring rate math, that R value gets squared, meaning that if your R = 0.5, your wheel rate or "effective" spring rate is 1/4th (0.25) of the rate marked on the spring. So your 750 lb/in springs would really roughly equate to 750/4 = 188 lbs/in. I suspect, again by eye, you are not quite 0.5 and maybe more like 200 lb/in effective rate.

For comparison, my 914 Porsche race car, with no engine in the front and pretty light corner weights on each wheel (~500 lbs on each wheel sitting in the garage) I had struts with 300 lb/in springs and now am converting to my own custom dual A design with an R ~ 0.55, so to get about the same effective spring rate I am going to 1000 lb/in springs on the front! The rear is nearly the same story with 1500 lb/in rear springs v. the old 550 lb/in setup I had (motion ratio was around 0.9 before).

Lots o info there but figured you might like to know that if you didn't already, otherwise, it's here for others edification