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Beer Geek
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Discussion Starter #1 (Edited)
Just drove it home today. It is an evolution of the high mileage/ stock drive train solution Groucho came up with over a year ago. The goal is to pick up as much handling agility as possible while giving up only a tiny little bit of ride comfort.

basic Groucho recipe:
stock GM springs
every bushing in the Pedder's catalog
Hotchkis bars
Koni yellows set to medium
18" wheels
good tires

There is a very thoughtful write up here:
http://www.ls1gto.com/forums/showthread.php?t=74410 . I have driven that car three times at least, at approximately 15k, 20k, and 30k miles after the upgrade. Not only does it handle better than stock, it lasts better than stock. The combination works very well with front cambers at -2.5°, and at 0.0°. Intermediate camber settings should be quite pleasing as well.

Not one to leave well enough alone, I started with a set of takeoff springs from a donor car with about 2,000 miles on it. With Herb Adam's Chassis Engineering (c. 1993, HP Books, NYC) open in one hand and an entry level 12 ton shop press I finished with ride heights of 597mm on three corners with 603mm on the left rear.

I had the major Pedder's bushings put in about 20k miles ago. AFAIK every bushing under the car today is either HKS or Pedder's, with the exception of the stuff on the rear toe rods Pedder's doesn't have in the catalog yet.

The Hotchkis bars I got, medium front, medium firm rear, I think seven coats of Zaino after two passes with the clay bar.

I was going to go with the Yellow Konis, really I was. One fact and three factors lead me to explore other avenues. The fact is the GTO is a 4000# car on 245mm tires. As a high mileage interstate guy, going to a staggered setup with 275mm rears and 245mm fronts costs me the ability to rotate, not good. The front Koni inserts actually fit inside what used to be the cylinder of the OE strut, I don't really need adjustable if the part is what I want out of the box, and Konis are a lot of money.

I am going to digress a minute here. Getting to know this subject matter has been quite interesting. Rather than try to turn my goat into a 4000# pound ballerina, I am looking to get it done so I can pick up a 2000# car...

So we had that whole thing with the '06 struts going on, and I read up on the Comfort Gas some. 'Near the top of the critical damping scale for OE springs' is about exactly what I am looking for out of Koni Yellows, for about half the price, and the bore/piston diameter on the CGs is about the same as OE instead of smaller, so to provide the same compression damping the CG doesn't have to work as hard as the Yellow Koni... So I drop a PM to Frank Beck out of the blue, with a cornering mode and a bump mode question, and he tells me what I want to hear. Then I called up Mike White and order up a set of four Pedder's CGs, without ever taking a test ride on them.

I am riding on 17" rims with General Exclaims, but I won't need to crack the rear cradle to change those. And my BMR sub frame connectors are finally welded in, I bought those things 106 weeks ago.

So to the basic recipe I added SFCs and subbed Pedder's CG for Koni Yellow. The rear CGs are currently back ordered in North America, so I am on 'good' OE rear shocks for now.

I called Dick Guldstrand's shop a couple times (http://www.corvettethunder.com ). They have done two Los Angeles area goats, same recipe, both are excellent. And I found the shop labor rate. Guldstrand's has done two goats that I know of.

Round trip airfare (southwest, open/unrestricted) LA to Oakland is $254. Mike White has serviced a couple hundred goats, and done probably 50 major suspension upgrades. I decided to bet on the guy with more experience who was also going to cost me less money.

So I dropped the car off at Dublin Motor Sports, and got 'THE CALL' yesterday.

Some observations about which I am certain:

I have picked up an enormous amount of high speed stability. At drop off my front ride heights (average) were 3mm higher than the rear. Now the average rear ride height is 3mm higher than the front. 6mm of change in rake. I actually did not have to explain my new suspension to any uniformed officers today. It is a noticeable improvement starting even at 60mph. Ordinarily I cruise in the high 70s to low 80s, today the car felt like it reached cruising speed with low 90s showing in the DIC. It used to be the front end would get light around 95, I didn't find enough room on I-5 to find the new limit. The new limit is somewhere north of 105. The SFCs are probably helping a little teeny bit to help maintain whatever low pressure zone I am developing under the nose, I think the adjusted ride heights are the bigger factor. If your car is low on the rear axle you may want to consider some spring shims...


On thoughtful spring placement alone my car is obviously wedged empty, and demonstrably de-wedged once I take the driver's seat. The car still prefers to enter left hand curves, and still prefers to exit right hand curves. However, the difference, the 'magnitude', of the preference is demonstrably dramatically reduced. Lesse, book $18.95, shop press 138.50, open minded installer free, better cornering, priceless. I shall commence interviewing 'navigators' in the 95-125# range more or less immediately.

On a curving, hilly two lane back road (near a buffalo ranch) between I-5 and US101 I went looking for the granny limit. Imagine your grandma in the front seat ready to tell you to slow down; and a carton of rotten eggs, but no unbroken shells, open on the back seat. At what speed will grandma speak up or an egg break? Its a 55mph zone, rural. Populated semi-rural it would be a 45mph road, suburban it would be 35 with heavily patrolled stretches of 20mph.

I got up to 5k in third gear (M6), shifted on up to fourth. A little faster, two more curves, a little faster, two more curves. I am up in the meat of the power band in 4th now, a little faster, two more curves. A little faster. I finally get a telegram from the rear suspension, 'Dear sir, we are beginning to function now instead of just enjoying the ride...', 88mph showing in the DIC.

Easing up to the limit and gently looking around for it, I suspect it is a little loose on the rear axle. But I expected that, I got stronger rear shocks on back order already, and those will stiffen the rear some. And while I did correctly ascertain which of my two rear springs was going to be taller, my guess on ride height was so far off I shouldn't have bothered guessing.

So while I am waiting on rear shocks I got go find a big empty parking lot, and then I can think about tuning the rear axle to the front axle one change at a time. I think I would be willing to back off the rear bar one notch if I could get enough other stiffness elsewhere.

NB: This setup works best on stock drive train goats, and we still get tire wear from camber squat. Less than stock, but we still get it. If you got enough hardware mods that you 'need' a tune to take advantage of your hard parts, the stock springs really need to get out from under your car, IMO.

Thanks to Mike and Pete at Dublin, Frank Beck at Rossi, and Justice Pete.

Scott
 

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I Hate Spunk
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swmn said:
I shall commence interviewing 'navigators' in the 95-125# range more or less immediately.
Scott
I've been watching your suspension saga fairly intently - there were a few spots I couldn't make myself try to understand, so I skimmed over them and hoped they weren't important - and wondered "what the hell is this guy up to?"

A few weeks, and tens of thousands of words later, I finally get it.

You're trying to pick up chicks.

If you'd just said so, I could have skipped all this. I want my four hours back. :soapbox:
 

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We enjoyed working on your GTO. It was a totally different approach than the normal make it handle like a slot car job. But I think we had great success in meeting your criteria. Your GTO was the first I have roadtested with the CG struts. They are not as performance oriented as our GSRs, but they really feel good and solid. I like the look of your GTO better now, than before. Raising the back end up a little makes it look normal to me. Again, I am pretty old school and rake. I did take your GTO home and went the back way thru some low speed light twisties, and it felt very responsive with great comfort. The only thing annoying was the darn radar detector going off.

You have a very sweet ride, especially for a GTO with 60K miles. It definately is far superior than any stock one out there.

Mike
dms
 

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Ignoring the Speed Limit
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BTW I've had my setup on the car for ~35,000 miles now (86,000 total on the car)...and still no squeaks or complaints.

Tear up some apexes, dude. :gears:
 

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Now that is useful data!

I'm curious as to what your current front and rear ride heights are versus stock.

Also, those sub-frame connectors... I'm eyeing those myself. How much do you feel they contributed to the overall improvement? Vital? Recommended? somewhat?
 

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Beer Geek
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Discussion Starter #9
Douggo said:
You're trying to pick up chicks.
You have the cart before the horse sir. I am going to pick up chicks to try and quantify the amount my car is de-wedged, without spending the $1,000 on corner scales. :judge:
 

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Discussion Starter #11
dms said:
You have a very sweet ride, especially for a GTO with 60K miles. It definately is far superior than any stock one out there.

Mike
dms
Well sir, you and I are the two that know exactly how far I still have to go to get my ride quality back. It isn't bad, but I want it better. There is no question the handling potential of the chassis is now unlocked.

When my rear CG shocks come in I going to ask you to back the rear bar off one notch towards softer at the same time.

I am fairly confident backing off one notch on the rear bar will put the car back in my comfort zone for ride stiffness. But it is going to cost me 'a lot' of roll stiffness.

I am going to get 'some' roll stiffness back with no ride stiffness penalty when new CGs replace 60k mile OE rear shocks, on balance the car probably won't handle quite as well as it does now, but the ride should be dramatically improved.

I am just waiting on those two things before I go tweaking anything else. Probably won't help to PM JusticePete everyday, will it?

PS: Feel free to turn the radar detector off if you want too. I have no idea how fast you really test drive customer's cars, the polite thing to do was leave it powered up. If it is my car you are test driving, I would appreciate you keeping your top speed below the redline in sixth.
 

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Discussion Starter #12
danrieke said:
I'm curious as to what your current front and rear ride heights are versus stock.
A factory new GTO still "down under" has a ride height around 605mm front and 610mm rear. Fresh off the boat in Cali they run about 605 and 605. At 60k miles with a 168# dummy in the car I was seeing about 577mm front and 572mm rear. Empty at 60k miles I was seeing 584mm front and 581mm rear.

Clearly the rear springs settle further and faster than the fronts.

danrieke said:
Also, those sub-frame connectors... I'm eyeing those myself. How much do you feel they contributed to the overall improvement? Vital? Recommended? somewhat?
I have no idea. This is my 8th vehicle with a GM smallblock around 350cid in it, but the first new car I ever bought and the first new car to get me on a GM lot since the turbo Buicks of yore. There are a bunch of reasons I took the depreciation hit, but I am keeping this car. Everyone 'knew' when the 04s came out that you put SFCs on V8 GM unibodies ASAP, before anything bends. We learned pretty quick the new goats aren't regular GM unibodies.

When my grandkids are ready to put me in a nursing home they can either straighten up, or I am going to sell the goat and take a trip to Vegas. And I am going to blow all that cash baby. Hookers, viagra, cocaine, $1000 black jack tables, you name it. With any luck at all I'll come home in a pine box with a permanent grin.

60k miles from now I would like to drop in a 383 stroker. With AFR 205s and and an AFR6016 cam I will probably make the top ten list for F.A.S.T class 2004 GTOs. Then, 180k miles from now, when the 383 is getting tired...

Someday I am going to be glad I got the SFCs on there before anything got bent. I bought them the first week I had the car. At 60k miles both my doors were sagging. Dublin Motor Sports fixed the door sag, replaced every bushing under the car, aligned the rear cradle, aligned the front cradle, aligned the transmission, all perfectly, called me up to assure me my floor pan was still in spec and I said, "Cool, weld those puppies in before anybody breathes on it!"

How long are you keeping yours? I am maintaining my car this year with an eye on resale value in 2056.

The second reason I put the SFCs in has to do with crash worthiness. I am going to have a full cage in the car before the 383 goes in. There are two kinds of cages. You got the inexpensive ones that weld to foot plates welded to the floorpan, and the really top quality roll cages that weld through the floor pan to welded in SFCs. I am getting the better quality rollcage, and my SFCs were welded in by Dublin Motor Sports at a moment when the car was in perfect alignment.

Third, I like a stealth street rod. I wanna drive my 383 GTO to church Sunday mornings and not have little old ladies kneel and cross themselves when I drive by in my black beast. So I need chambered mufflers, and some space, and I am going to have to do some more math. But I bought an inch of vertical space with the SFCs. It is actually 3/4" at the front and 1 5/16" at the rear, I am thinking of it as one inch.

If I do get any suspension stiffness from the SFCs it wasn't one of the top three reasons I did it.
 

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Ignoring the Speed Limit
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Don't forget the Pedder's sway bar endlinks. They're a gotta-have if you flog the twisties at all.

Did an undercar inspection a couple of w/e ago when I changed my oil and they are still nice and straight, even after some hard driving through the aforementioned Little Tujunga, the Angeles Crest, and a stint on the Castaic stretch of The Ridge Road.
 

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Discussion Starter #14 (Edited)
Groucho said:
Don't forget the Pedder's sway bar endlinks.
I got those. The only factory suspension components left under the car are four lower control arms, two radius rods, two toe rods, two ball joints and the rear shocks I have back ordered.

The ball joints were on the list of items to possibly replace, but they passed muster for another 60k miles. I picked up a pair at Midwest's moving sale cheap, I am just keeping them until I do need them.

EDIT: And I had to re-use some of the dinky stuff, rear sway bar saddle brackets, rear sway bar endlinks (got fresh bushes on those) and the factory rubber bits on the rear toe rods are still installed.
 

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Missing my little one.
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:thumbs: Awesome swmn, very awesome.

Great write-up!
 
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