Bluewasp

HI, Since my front and rear suspension rebuild I've noticed a massive amounts of oversteer.. I noticed that if I have less then 1/8 tank of gas the oversteer is reduced but if I drive with a full tank the oversteer increases and is somewhat squirrelly... I have an 80 with new front springs and 9 leaf spring in back.

The Front sway bar required the largest bushing Zip Products sells. Can't remember the size, but the bar is HUGE, and I DON"T have rear sway bar. Car didn't come with one. I want to install a rear sway bar but not sure on what size... I assume, that by installing a rear sway bar I will reduce the amount of oversteer?? OR Do I need to reduce the size of the front sway bar? how can I balance to Neutral Steer ????


[Modified by Bluewasp, 1:07 AM 9/1/2002]

Colin

I'm a little foggy on swaybar setups because it's been awhile since I dealt with mine, and it's late but I believe you need to get a smaller front bar.

Colin

Shark Racer

Staggered size tires can induce oversteer. (Having smaller tires in front than in back.)

Countering this, make sure your front tires have more grip than your rear. If you're running the same size tires all around, keep the good tread up front. Bigger front springs will help promote more understeer, although the amount is sometimes considered negligible. Removing weight on the rear axle helps too. Get rid of the spare tire carrier, and you'll probably cut about the same amount of weight as if you'd dropped half a tank of gas.

-Steve


[Modified by Pacin'California, 12:26 AM 9/1/2002]

Colin

To clear up term meanings-
Oversteer is when the back of the car breaks traction. Fishtail is a minor form of oversteer. If you're in a turn, mash the gas pedal and the rear kicks out, that is oversteer. The car steers or turns too much. Letting off the gas and counter steering takes care of the problem.

Understeer is when the front breaks traction. It won't turn. You just keep going straight and lose your steering ability. Happens if you enter the turn too fast. Only way to get out of it is hang on and steer where you want to go. You just have to wait for the speed to come down enough for the front tires to hook up. Hitting the brakes isn't good because you'll lock up the front wheels and keep sliding straight ahead.

Colin

Turbo-Jet

Oversteer in a steady state corner is not a safe thing. To eliminate this, you have to reduce the rear roll stiffness and/or increase the front roll stiffness. This is odd as you have a large front sway bar, and no rear... What rear spring rate are you using? (stock?) Check the rear alignment? Maybe you have excessive toe-out?


[Modified by Turbo-Jet, 2:49 AM 9/1/2002]

mrvette

I have a suspicion our original poster, thread starter, has the terms confused...and in fact is under steering....he needs a rear sway bar...

GENE

flynhi

My experience has been that C3s are very sensitive to proper sprng and stabar balance. If any of the four (front and rear springs, front and rear stabar) is out of balance, the result is poor performance.
First, you need to determine what your goal is - street use, aggressive street with occasional auto cross, amatuer racing or full race. Each will have a different setup.
Next, check OE setup for this design goal.
Next, check with Guldstrand and VBP to see what they recommend. Guldstrand's catalog has an excellent section on vehicle dynamics that will help you decide.
In stabars, bigger is not always better. A small increase in stabar diameter will have a major increase in rate. For example, a 3/4" rear bar will have over twice the rate of a 5/8" bar. See the Addco website for a chart that compares several bar sizes. VB sells Addco bars.
IMHO, you are better off to go smaller and work your way up rather than V-V. There is some expense in doing this, but the result will be worth it.


[Modified by flynhi, 10:33 PM 9/1/2002]

Bluewasp

Everyone: Thanks for your comments...

let me try to describe...... With a full tank of gas going into the turn. The front end seems to turn at a sharper angle then the rear... I have to turn the wheel the other direction to correct...


Oversteer is when you turn the wheel and the turn angle is sharp??? Understeer is when you turn the wheel the car wants to go straight?



[Modified by Bluewasp, 12:09 PM 9/1/2002]

Bluewasp

My goal is Street/Street Performance. No road racing or auto-x, but not a caddy feel either.

As for the spring rates. I'm not sure which springs zip sent me in the kit. I told them what year and what I wanted, but I'm thinking they might be the heavier ones and some of my oversteer is caused by a heavy front spring and the soft 9 leaf in the rear... But with a softer spring in the rear wouldn't the car have lots of understeer??


The car was balanced perfect when I bought it other then it needed the whole front and rear rebuilt. I want the feeling I had when I bought the car minus all the noise and vibration. :D


[Modified by Bluewasp, 12:08 PM 9/1/2002]


[Modified by Bluewasp, 12:12 PM 9/1/2002]

73 LS-4

I'm guessing that you are running with a 1 1/4" front bar and no rear bar. 1 1/4 is probably too big for a small block car unless our really serious into cornering, especially without a rear bar. I run a 1 1/4 front and 3/4 rear bar on my car but mines probably a couple hundred pounds heavier as well with the 454 up front. I think there's one of two ways you can go about this, either drop your front bar down to a 1 1/8 and go with a 5/8 rear bar (probably optimum for an 80 street car and probably comparable to my setup which I really like). Or you can stick with the 1 1/4 bar and go with either the 3/4 (this would probably remove almost all bodyroll out of the car and make it more uncomfortable on the street), or try a 5/8 bar in the back as a sort of compromise, but I feel with this setup you'll still get some oversteer. I think your best setu is the first one I mentioned, you could possibly sell your 1 1/4 and then get your 1 1/8 and 5/8 bars. I could imagine it's a handfull right now, probably feels like the rear end wants to twist itself out of the corner as the rear wants to roll why the front wants to stay flat. I got a great deal on my rear bar first so I installed it with a stock front bar and had the opposite problem, bad understeer ( I didn't take nay corners fast for a while) which is even worse, the front bar fixed the problem.

:cheers:
Pat Kunz

mrvette

When I built this car's suspension some 7 years ago, the car was done with VBP products....480 ft springs, 1.25 inch bar, 330 lbs plastic in rear with 3/4 inch bar....urethane thoughout everything....
17 inch wheels....

rides stiff as hell....wife don't like it, schoolyard rumble strips on the roads make it hard....need to go 30+ mph in order to ride over them....

OK, too stiff.....I"m thinking of removing the bars, going 1.125 up front, maybe thinner, leaving nothing in rear....for starters....and IF I have to going looser at stock front springs....any suggestions anyone???
OH my shocks are KYB's all around...still good, don't leak anyway...

GENE

Colin

mrvette- You springs and/or shocks are too stiff. Swaybars don't have a big affect on ride harshness over bumps in a straight line. Springs have a decent affect, but shocks have the most affect.

Colin

Lohkay

Bluewasp...from your description, what you're experiencing is oversteer. The back tires are losing traction... So yes, adding a rear sway bar will help your situation a lot. I run the fatest sway bars front and rear and I feel I have the perfect balance for my car... I run the 1 1/4 front and 7/8 rear. If you don't want a rear sway bar, reduce the size of the front one.

flynhi

Mr vette,
Sounds like your wife wants the OE street ride and you want something a bit stiffer.
Generally speaking, for street performance use, you want softer springs and medium stiff stabars. This will permit a comfortable ride but control body roll in a turn.
You might try OE BB coil springs from Corvette Central at about 330 lbs and the OE rear 9 leaf steel spring. I'd match these with 1 1/8" front stabar and no rear. Your KYBs are probably OK even tho a bit stiff. If you want a soft but controlled ride, try Konis.
If $ are not a problem, try a TRW 315 rear spring with the VBP front fiberglass spring set on softest setting. 1 1/8" up front with 5/8" in rear with Bilstein Sport shocks. Try BFG T/As 245/60/15s up front and 255/60/15s in back with 28 lbs pressure.
Poly bushings all around.
Either of the set ups above should give you the ride you want.
Disclaimer: I'm just an experienced amatuer at this - you really should talk to Guldstrand for the best advice!


[Modified by flynhi, 10:42 PM 9/1/2002]

Bluewasp

Everyone: Thanks for your additional posts and comments.

As for the size of the front bar. I'm not sure but its just as large as a Z06 sway bar. I know zip sent me the stock 1980 front bar bushings and I laughed when I saw them.

Does anyone here know of someone selling a rear bar? The suggestion of trying out different bars would seem to cost major $$$$..

I had another thought....... The front end links that the sway bar attaches to... If I tighten or loosen the bolt would that increase or decrease the effectiveness of the front sway bar???? I'm think that if I back off the nut a little the bar would have more room between the bushings and the car would sway more in the turns... Thoughts.... ???????

Bluewasp

Its not to bad... but I can't take turns to fast! :( The back hasn't broken loose as in the tires are just sliding back there... It's more of a wet noodle rear end.. Like the rear end has to think for a few seconds if it wants to follow the car in the turn... Or if the rear is attached to the car on a rubber band...

What I don't understand is how the car is unbalanced now... If I just replaced the springs, stocks, etc... hmmm...why would the car be unbalanced… ???? I wonder if the other owner put the thicker bar up front because the springs were shot. When I applied the breaks before I did the rebuild the front spoiler would slam into the ground.

no_radio

I had KYBs on my '74 when I first rebuilt the suspension. With stiffer coils and fiberglass monoleaf on new rubber bushings the car felt every pebble and expansion joint, really busy ride.
I switched to Bilsteins last year, and with no other changes the ride became pleasant. The handling is as good if not better, but the ride is WAY better. They are about twice as much as the KYBs, but worth it to me.
Jeff

Colin

Do NOT do that! It may seem like a good idea, but a loose swaybar is NOT good. Basically what will happen is you will get a tiny bit of body roll, then BAM! The car will be just as hard, but with a jolt. That jolt will most likely upset the car causing even more problems.

To fix your problem- Get a smaller front bar, and put on a rear bar. You can sell the front bar to offset your costs.

I'm sorry but I had to lol when you said that hitting the brakes would cause the spoiler to slam into the ground. lol I do believe you are right in your thoughts that the other owner put it on to make up for more than lacking springs.

Colin

73 LS-4

What I don't understand is how the car is unbalanced now... [/QUOTE]

The reason it's unbalanced is that the swaybar tries to distribute the load in a turn to both sides of the suspension rather then just one side, the lighter the bar the more initial give you have therefore the more suspension travel you have on one side before it starts applying substantial pressure to the other. With a real thick bar it takes very little suspension movement before it starts applying substantial pressure to the other side. So in a way a thick swaybar can make up for weak front springs in a cornering situation, since it's applying pressure to both springs quickly, distributing the turning load better, rather then just one spring taking almost all of the load without a swaybar. Now look at this in how it applies to your car with new springs up front. As you go into a left hand corner the right side spring takes most of the brunt of the suspension load as the suspension gives the slack is taken out of the swaybar links if there is any and it starts applying pressure to the spring on the right front and at a certain point the spring load across both springs is equal to the amount they can support at the current height and bodyroll stops in the front. Now you go the rear, without a swaybar each end of the spring supports the weight of the roll pretty much independently, if you have equal rated springs front and rear , the rear without the swaybar will roll quite a bit more since it's not distributing the weight across both sides like the front. There are adjustable end links, that have springs instead of solid stell tubes which can be adjusted for some initial give before working against the swaybar, so at least initially it will act like a smaller swaybar.



:cheers:
Pat Kunz

redvetracr

Bluewasp,
If you or anyone else is interested I have a brand new NOS/GM factory 7/16 rear bar $100+UPS PLEASE e-mail direct!! redvetracr@msn.com