Günther-C3

Hi all!

I know to change the shocks, springs and monospring is a good upgrade and to rebuild the steeringbox also, but I mean what else is a required upgrade?
Times ago I saw tubular a-arms which you can adjust more caster. Is this a reasonable upgrade? How much determines the caster how the car drives straight ahead?

Regards, Günther

7T1vette

Gunther-C3....

That depends on what you want to do with the car, Gunther. If you plan on doing some weekend road racing, you need to put some better "stuff" underneath. But, if you just want it to handle well on public roads, refurbishing it to original condition will suit your needs just fine. You can spend as much money as you want on 'whiz-bang' suspension equipment--but if you are not going to do any serious driving, it will just be for 'looks' and never get used. The stock suspension [when in like-new condition] handled just fine, IMO.

Shark Racer

I agree with this. A lot of money is dumped into make the car "handle like a dream", when you're really dumping tons of cash into slight incremental differences that wouldn't be appreciated without a clock involved.

gkull

I personally like adjustability. So I installed the front QA-1 dual adjust semi coil over shocks with Speed Directs 600 pound springs for the street and 700 pound for the track. Very easy to set any ride height.

As for caster settings. About 4.0 is the max you can get with the stock setup. You can unbolt upper A-Arm bar by removing the nuts where the shims are and machine out 1/4 inch elongating the hole. This gives you the ability to dial in about 6.5 degrees of caster. The additional caster and the downforce on my front end makes my car very stable while driving around at 260 Kph.

Caster is the tilting of the uppermost point of the steering axis either forward or backward (when viewed from the side of the vehicle). A backward tilt is positive (+) and a forward tilt is negative (-). Caster influences directional control of the steering but does not affect the tire wear and is adjustable on our vettes. Caster is affected by the vehicle height, therefore it is important to keep the body at its designed height. Overloading the vehicle or a weak or sagging rear spring will affect caster. When the rear of the vehicle is lower than its designated trim height, the front suspension moves to a more positive caster. If the rear of the vehicle is higher than its designated trim height, the front suspension moves to a less positive caster. With too little positive caster, steering may be touchy at high speed and wheel returnability may be diminished when coming out of a turn. If one wheel has more positive caster than the other, that wheel will pull toward the center of the vehicle. This condition will cause the vehicle to pull or lead to the side with the least amount of positive caster.

Günther-C3

Thanks guys for your replies!
My suspension is almost new, on the rear I have a new VBP monospring, on the front I have 550´s springs with edelbrock shocks on all 4 corners. And I converted to the borgeson box.
I don´t drive her on a racetrack, but sometimes pretty "sporty" on the highway.
The issue I have is when I drive aprox. above 60 mph, the steering becomes touchy
A few weeks ago I was at a shop which adjusted the suspension, but they didn´t adjust the caster.
Could this be the reason why it feels touchy?

Thanks, Günther

gkull

You want a 1/8 - 1/4 inch of front toe in .40 or so neg camber and caster should be set to as near 4.0 pos as you can get.

The toe and the big caster numbers make a car more stable.

7T1vette

You need a little "toe-in" with a light car on wide tires. Otherwise, it will 'walk around' at speed. About 3-4mm (1/8"-3/16") will do it on a street-driven car. Any more than that will start wearing the front tires excessively. Make the toe-in adjustment, then see if that improves things. If you still have some 'wandering' with the steering, check the condition of the following: flex coupling just before the steering box (ragjoint); looseness in any of the steering rods/knuckles; ball joint wear; uneven front tire wear.

pauldana

BIGGER front sway bar, add rear sway bar if you dont have one, if you do, change it one size up also....This made a BIG difference in the way the car handled in the curves and twistsies,,,,and a cheap but less obvious upgrade would be the spreader bar,

sounds like you got good shocks (although I like the Bilsten Sport's the best) and the right springs. But I would have gone to the Rack&Pinion, it is a much better system and very easy to install...

So... Sway bars!!!....... and R&P


ps.... my next step is getting away from the 15" rims which nobody makes a good high performance tire for.... and going 18", with some good V rated tires....

73ls1

I am going to install the Van Steel coilover kit. I think I can get the result that I want. In Nov. I will be selling my Vette Brakes competion plus kit and 4 QA1 double adjustable shocks. Charlie

TheSkunkWorks

Springs, shocks and bars are all relative one another, and the right comination depends as much on your ultimate purposes as on your vehicle's weight distribution, the type of roads you're aiming at and your driving style and ability. So it is that you'll eventually have to do some testing to get honed in on what's best for you, and likely end up with a few redundant bits left over. To that end...

Do as much anti-roll control as you can stand with springs, as they don't carry the same penalty in reducing cornering capacity as do massive bars, and bars don't do a thing for squat or dive. I'd think of bar(s) more for final balance tuning rather than as the primary device. Oh, and you might find you don't need a rear bar when you get right down to it.
If you're serious about fine tuning to optimize handling, go with adjustable shocks. QA's seem to have a good rep. I like KONI, especially their support. True double-adjustables would be a good call if you can swing them.
I'd also look at lowring as near to Chevy Power RR specs as you can, if you haven't already.
Up front I'd install bump steer blocks, and out back I'd drop your rear camber strut links at the diff bracket ~1/2" lower than OEM. (More than 1/2" might work, but I wouldn't suggest going further without methodical testing.)
As for caster, IMCO you really don't need more that ~2-3* with manual steering.
It should go without saying that the better your tires, the more you'll get out of anything else you do to improve your chassis. Get a pyrometer so you can read them accurately.
There's more, of course, but hope that's worth $.02


TSW

elle88

Hello Gunther
if i recall correctly your car is quite low riding. this means you should address first some geometry issues related to this : bump steer blocks in the front and raising the differential at rear or tune the rear toe in to 1/4" or so if you leave the diff as it is.
I have no experience with the borgeson box but my car has become really stable at speed only the day i went to manual steering and replaced all the critical parts in the steering-suspensions

Jim_Harrison

1/8 to a 1/4 FRONT toe in? I always ran a little toe out in front and about 1/4 toe in, in the rear. Seams to me a street car should be neutral for tire wear. I agree the caster will help.

gkull

He was talking about stability problems even at slower speed. I run "zero" in front and I used to have "zero" rear Then I changed the rear shimming to .100 per side for laping.

Solid LT1

I use a little toe-out when autocrossing my Vette but, for street, I go 1/8" toe-in for high speed stability while freeway driving or Drag racing. Given he lives near an Autobahn, I would use a little toe-in on my C3 Vette. For the rear DEFINATLEY go with atleast 3/16" toe-in if not 1/4" (6mm) as any high HP IRS car needs the stability that toe-in will give the suspension.

Günther-C3

What are "bump steer blocks"?

Thanks, Günther

gkull

You can read up on "bump steer" But you want your front tires to have no toe change while encountering vertical travel.

http://www.vbandp.com/C2-C3-Corvette...Steer-Kit.html

http://www.longacreracing.com/articl...sp?artid=13#Q1

carbster09

Gunther,

That is a nice looking ride. The next time I am passing through Salzburg I will be stopping by for a beer!

Of course the last time i was there was something like ..... 15 years ago after Octoberfest

carbster

OzzyTom

Like one of the original replies stated, getting the suspension back to near new condition is the first consideration.

No one made any mention of the suspension bushes.....
I replaced all the suspension bushes in the front and rear components as well as the ball joints, as they were showing their age.
As its street driven, I opted for rubber, not polyurethane.

Very noticeable difference in steering response and handling.
And a hell of a lot more comfortable over road irregularities too!

Get the basic suspension back in good order before considering suspension modifications. You might find it's all you need.

TheSkunkWorks

Guess I (we) more or less assumed his bushes were in good repair, but your point is certainly a valid one.

Solid LT1

If I lived in Austria like the poster, with the high speed Autobahns near, I would run at least 1/8" of toe-in maybe 3/16-1/4" for good measure while also adding the 4 degrees positive Caster recommended.

Now if I were Autocrossing going under 75MPH in a parking lot, I would have "zero toe" on a street car and toe-out on a trailered race Vette with around 2 degrees of positive caster along with a little yellow stripe on the top center of my steering wheel to show me where dead forward is

For street driving my camber setting are usually:1degree negative max front, 1/2 degree negative rear (3/16-1/4" toe-in a the rear suspension.)
Camber would be determined by my observed tire temps on my Autocross Vette (no I'm not taking temps for street driving) but my "ballpark settings" are: 2 1/4 degrees negative front (my rims are skinny 9" wide ones) and 1.5 degrees negative at the back unless I have problems with the tires smoking off of slow corners, then backing off to 1 1/4 negative.