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Discussion Starter #1
Many of the photos we've seen of the GT racing or otherwise demonstrating its handling abilities also show an awful lot of body roll. Also, for what I have read this car pushes a lot!

Sportier suspension components are available, but a LeMons car has a budget that makes buying any of that really nice stuff impossible. So we are considering our options.

For the front, we'll fabricate shackles to lower the car, but for spring rate, the only thing we can think of is shoving a wedge of rubber up over the leaf springs. That will in effect shorten them, making them stiffer.

In the rear, cutting the springs come to mind and that should lower and stiffen them. (I need to check my formulas on this.) I've read here that the stock springs have 150 ppi spring rates and that the sportier variety are in the 180 - 2000 ppi range. If we need additional stiffness back there I'm thinking of inserting spring rubbers, ala NASCAR.

Obviously this is going to take a little testing to see if any of this actually works, that is, doesn't make things worse. Seat of pants suspension tuning.

These may sound like ridiculous ideas, and if so, say so. I'd really appreciate any input people might have.

Some specific questions. With a rear spring rate of 150 ppi and a near 55/45 weight distribution, is it safe to assume that the spring rates in front are just slightly greater than 150?

Another. How difficult do you think it would be to fab our own sway bar? Seems it would only require bending a steel rod, end links, and mounts. Hopefully we can find off-the-self mounts. Also, please recommend a bar diameter. (I think I'll google to learn a little more about sway bar design.)

Thanks.
 

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Rear sway bars from Kadetts can be used. You'll either need to cut the brackets from the Kadett rear diff. hsg. or be really lucky and your GT already has them on it. Does shipping count in the purchase price?

Harold
 

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Another way of getter stiffer springs for the rear of a GT, especially on the cheap, throw a set of Manta or Sportwagon springs in the back.
 

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Discussion Starter #4 (Edited)
Thanks, all.

I spent a lot of time last night reading the older posts here on suspension work and I can see I can easily make things worse doing only what the tuner kids think is essential, just lowering and stiffening. We haven't even driven the car yet so we don't even have seat-of-pants data yet to even know if we've made things better or worse, but we're pretty sure we are going to want to do something, again, based on the photos we have seen. Then again, the Opel GT racing history book I have doesn't talk much about suspension at all, so does this mean they raced and rallied on stock suspensions?

Our budget will not list shipping, taxes, the cost of 20 trips to Harbor Freight or driving to Vallejo and Stockton and Richmond for parts.

Edit - I'll check the car to see what the rear sway bar mounting options are.
 

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'72 Opel GT (Sara)
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...Then again, the Opel GT racing history book I have doesn't talk much about suspension at all, so does this mean they raced and rallied on stock suspensions?
Go to this link for the OGTS catalog version 8 and see page 42. I think anti-sway bars and wider tires were the primary methods used to get better handling (in combination I'm sure with lowering the stance).

HTH,

Matt
 

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Sportier suspension components are available, but a LeMons car has a budget that makes buying any of that really nice stuff impossible. So we are considering our options.
If you show up with a GT, I can almost guarantee they will weld something ridiculous on top of it.

Bill
 

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Track width

On the stock GT you will find that the front track width is narrower than the rear, by 0.6" IIRC. So you need to add spacers and probably change the offset of the front wheels. The narrow front track contributes to understeer. Also, nothing helps handling like a good Autocross alignment!!!
 

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Then again, the Opel GT racing history book I have doesn't talk much about suspension at all, so does this mean they raced and rallied on stock suspensions?

Hardly. But by today's standards they were pretty tame mods. They usually used the factory sway bars (in Europe they were standard, but not in North America), and often fitted monoball for suspension bushings (i.e., spherical bearings), usually Koni racing shocks (sometimes Bilsteins), sometimes 'zugstrebe' bars up front to reinforce the weak lower a-arms, often a rear watts linkage in lieu of a panhard bar, and sometimes they played with the roll center heights.

IIRC, Conrero used the standard front transverse leaf spring, but simply welded tabs onto the bottom of the lower control arms with additional holes in them. This was done to lower the front of the car.

Some of the simplest gains in a GT are by employing weight distribution techniques and correcting the geometry. Of course good bushings don't hurt either!

BTW, what type of course will the car run on? An oval track or a road racing course? I ask because there are different philosophies regarding suspension for each venue. If it's an oval track, then you don't want a rear sway bar, and the alignment will be completely different too.
 

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Discussion Starter #9 (Edited)
The courses will be road course, Thunderhill, Infineon, Buttonwillow, and probably Reno-Fernley. It will also probably autox locally.

We're definitely going to lower the front the way you suggested, then we'll add an air damn and splitter.

Our budget won't allow for a sway bar, unless we made it ourselves, or unless it looked like it had been out in a field for 30 years and made of cheatonium.

0.6" track difference make that's much difference in handling?
 

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Our budget won't allow for a sway bar, unless we made it ourselves, or unless it looked like it had been out in a field for 30 years and made of cheatonium.
Easy enough to adapt a Manta rear sway bar. They're 14 mm (9/16" basically), and very common. I have 20 of them in my storage probably. I just installed one on my friend's '69 Camaro in fact.

0.6" track difference make that's much difference in handling?
Well, for starters a GT has a narrower track up front than out back. A Manta by comparison has a wider front track than out back. In order to make up for that difference, you'd have to make the front track 1.2" wider in your GT!
 
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