Sorry guys, but as a road racer myself, and considering the way my car runs with the 1 1/8in front bar and 3/4 rear with 550 front springs and 360 monorear with Bilsteins HD's in the front and Bilstein Sports in the rear on the street, I still do not buy the no rear sway bar argument for the street. Oversteer at very high limits is not a bad thing. Much of it depends on your car's configuration, tires, spring rates, etc. At the risk of everyone's rath, most people on the street and racing feel that understeer is easier to control than oversteer. If oversteer is not your thing, naturally you will be faster with the car plowing. As for big block C3's handling BETTER with no rear bar, I am completely baffled since the car is VERY nose heavy to begin with and coupled with high torque and horsepower would make the car plow like a snowplow without a rear bar at the limit. Based on the comments I have read here, I should disconnect my Eibach rear bar on the IRS of my 300 since it will eliminate the oversteer at the limit and thus the car will be faster. I hear everyone's comments but the science just does not add up based on handling dynamics and my own real word experience. People who are interested in upgrading their rear bar or adding one would probably best off talking to any number of reputable vendors that have tons of experience with their suspension kits such as VBP, Mid America, Ecklers, Corvette America, etc. GM put rear bars on street vettes for a reason and it wasn't because it made them look good and it certainly wasn't to slow them down! Think about it!

 

It's much easier to press a car to the limit that isn't trying to bite you in the a$$ all the time, especially if you tend to do much spirited driving on the open road. Those limits can be surprisingly far out there in well setup C2/C3, too. But, as mentioned earlier by greg75vette, most drivers really don't have a clue as to what that means and even fewer understand Vehicle Dynamics.


I have done considerably more than simply thought about this...

I don't contend that it's right for every application, but the NO REAR BAR "argument" is fundamentally sound, both in theory and in fact. Optimum roll couple distribution (a.k.a. "balance") can most certainly be achieved without a rear bar. Both bars and springs contribute to roll stiffness, so you can't ignore one when discussing the other. That the factory and others have generally chosen more bar over higher spring rate (550# front coils are still relatively mild in this context) as their preferred method to increase roll stiffness is not proof that the same cannot be had by going with higher spring rate while keeping bar to a minimum. This latter approach pays the dividend of less lateral weight transfer (besides, bars do nothing to counter dive or squat).

Theory and my personal experiences (track and street) aside, Dick Guldstrand put the "big front spring/standard front bar/no rear bar" philosophy (for lack of a more succinct name) to the test when successfully campaigning his own SCCA A Prod BB/C3. His advice helped me in from the wilderness of my own misconceptions when chasing my SA's setup. Too Too bad most owners will never experience what C2/C3 properly sprung for high-performance handling is really capable of...

 

Besides all that, the factory never offered rear bars bigger than 7/16" and 9/16" as far as I know; not even approaching the big mother f'er 5/8, 3/4, and 7/8" bars offered by vendors. Who needs a bar that big?? The factory or Duntov rather must have known something about pushing these cars to the limit. And if you're not pushing the limit, then why add a rear bar? They can and will bite unexpectedly. I found out the hard way when I put a 3/4" bar on my dad's car because it was the "matched" rear to the 1-1/8 front. It lasted all of about 1 hour on the car before it was disconnected.

Also the aftermarket rear bar linkage can bind the suspension and preload it. The factory linkage is suprisingly neutral.

FWIW I use a stock 7/16" rear bar with 1-1/8" front. I wouldn't go larger than what the factory ever offered.

 

I would like to hear the thoughts of owners of street vettes with aftermarket rear bars. Any thoughts from all of you out there with 5/8, 3/4 or 7/8 inch rear bars? I have run the factory 1 1/8 in front bar with poly mounting bushings and end link bushings (which effectively mimics the action of a larger bar) and a 3/4 inch rear bar with poly mounting bushings with the factory linkage for many years with 550 in front springs and a 360 mono rear spring for many years with zero issues. I am VERY pleased with the balance and like many of you road race formula dodges (engine in the rear) which, by the way, has a rear sway bar. I think the point of not going larger than a factory 9/16 in rear bar is probably good advice for many but I still disagree with no rear bar for street vettes, as a general rule. Just my opinion, to each his own! I would like to hear some vendor opinions as well?

 

Years ago when I first purchased my 76 it came with I believe a 7/8" front and no rear bar. Coming from GM "G" body cars that had horrible understeer I made the mistake of getting the largest sway bars available for the vette 1 1/4" front and 7/8" rear. This combined with the transverse springs (on the softest settings) made the car a nightmare in my opinion. The swaybars were so stiff that the car had a harsh ride even with the soft spring rates. When I pushed the car hard on the street it cornered VERY flat until ....... HUGE oversteer with no warning resulting in two spins costing me a back bumper.

Now years later, and after a lot of research, several SAE siminars, and advice from guys like 69autoXr, Skunkworks, Jim_Harrison my car is finally balanced and is quite "neutral". Since my car is a multi-purpose vehicle (weekend cruising, vacations, drag racing, and HPDE's), I've had to make a lot of compromises. I won't go into my whole setup here, but I ended up using a 1" front bar and a 9/16" rear bar.

If my car was more of a true track car, I would go with stiffer springs which I'm sure would affect my chose of sway bars.

 

3/4" rear bars are for trucks, thats where mine went

Also I've never seen anything bigger than a factory bar on a race car, and I've seen quite a few.

 

There is no fundamental reason why a rear bar is REQUIRED. It is 100% dependent on the complete chassis setup.

fwiw, I have a 1 1/4 front and no rear bar on my '69. Removing the 3/4 rear bar I had on it dropped my autox time at Cruise In by something over 1/2 second. But me saying that is meaningless because you don't know what springs I'm running. Regardless, a rear bar is not required in all setups.

 

I bought my 79 vette new. Not allot was sold to make them better back then. You had no internet. My car was not a grand sport. this new company offered an handling package with 1 1/8th front and 550# front springs with 360 rear and 3/4 sway

I drove that combo for years with upgraded wider tires and hot rodded motors.

After 20 some years I took off my spring adjustable 3/4 rear sway and a punctured rear road racing slick stopped my test. I decided to just strap my 315X17 wheels back on and just do the day for SCCA year end points.

IMO- the 3/4 sway was much more beneficial than running without one.

If you are using 255X15 or less tires on your Vette lots of your problems are not sway bars, but old greasy tires. I run Z rated and they are only good for few heat cycles. I mean AA traction and A temp. Everything comes down to tires. Why do you think that a race cars changes them within 20 laps.

I really think that lack of body roll and the additional bracing of the sway bar on the trailing arm helps. so I'm pro sway bar in cars with quality tires

 

Gskull, you make a very good point about tires. I am less inclined to favor the rear sway bar on C3 street vettes than I did with the old former 255/60/15 Radial T/A's S-rated tires I was running with my suspension modifications than I am now. I recently switched to 17 inch SLP's with 255/45/17's Z-rated in the front and 255/50/17's in the rear, Kumho's. The main reason for the rim switch was to finally get some excellent tires on the suspension which could take more advantage of the suspension tweaks I had made over the years. The olders tires were not up to the task of the suspension. Tires are the single most important limiting factor in the suspension. Clearly, the road racer/autocrossing crowd does not favor running a rear bar along with those who tell of spinning their vettes on the street. I still believe that this phenomenon is more a result of the very different weight distribution of the vette than of the presence or lack therof of a rear bar. A friend with a 79 tells of a spinning exit ramp story of his vette with the base suspension and no rear bar, as an example. Porsche 911's with the engine in the back run a rear bar along with a front bar and are very quick on the track, despite their rear weight bias. You cannot drive a 911 like a front heavy front wheel driver, if you want to go fast. Can anyone explain why all performance cars both current and going back to the 70's almost universally have balanced front and rear bars, regardless of the car type? It is almost unheard of to see a car running just a front and/or rear bar alone on the street. With that said, this discussion has certainly been informative.

 

The Porsche 911 story, while possibly interesting, is completely irrelevant. Same with comparisons to other vehicles. Without knowing the suspension geometry and spring rates for those other cars, comparing stabilizer bar sizes isn't possible.

Saying that a factory-built C3 without a rear stabilizer bar isn't balanced is incorrect.

 

Maybe you misunderstood! And your explanation for just about every performance car for the past 30 years up until the present having BOTH front and rear sway bars in a balanced package is???? You clearly don't understand the 911 analogy either based on your comments.

 

IMHO, it really comes down to personal preference of how you want the car to behave and your intended use. Maybe a big rear bar does let you handle flat up to the edge, but the biggest thing that I didn't care for was the lack of feed back .... which for a novice is not such a good thing. I think that fits most people on here that do this as a hobby and are not pro's (there are several exceptions ... no offense intended to the actual racers on here).

Using smaller sway bars (at least for me .... a novice) allows the car to give me more feed back on the track. I can tell much easier when I'm nearing the limit, which allows me to run faster and safer because I am more confident in the car.

 

Your car is all over the place in the corners

 

Clearly you are using bubba science

 

I've been working this year on smooth driving and throttle control. I have not posted a video from the last three race weekends.

I also go out and have fun and try different things on each turn to see what works best

 

gkull, I really wish I could convince you to test out 700's up front with less overall bar (and perhaps a step less rear spring, what with the power you obviously have on tap) on your shark before you retire it from track days.

 

My two cents! After installing Steeroids R/P and lowed the front springs. In the mountains of Tenn. on my way to Bowling Green. I noticed that going down hill left turn the front right would dip, and the left rear would lift. I was running with C5/C6's we were hooked up. The opposite when turning right. A little dip going up hill and turning. No where near as bad as going down. So I installed a spreader bar from VBP. Drove to Carlisle last month. It handled the turns better. I talked to VBP and told them the same. They suggested I install the 1-1/4" front and 3/4" rear. I've done that. it handles fine on highway exits. That all the turns we have here in south Florida. The real test will be Bowling Green next spring. Did I mention. The only thing stock on my 78 L-82 is the interior.

 

Oh believe me, I understand the 911 analogy quite well. What's missing from the puzzle is the 911's suspension topology. Exactly how much roll stiffness do they get from the springs and how does that compare to the C3 suspension design? How much roll stiffness in addition to that from the springs do they need? As I said before, the simple fact that a 911 has a stabilizer bar is totally irrelevant. Same goes for "just about every performance car for the past 30 years". You simply can't look at a feature list and see that most have a rear sta-bar and declare that they all need a rear sta-bar. There is far more to it than that.

 

I beleive this is the last time I will add my experience to the sway bar issue. First my car is very balanced, one 4 corners scales with me in the car there is only a 22lb differene between the weight on the four tires, could probably be a little better is I spent more time adusting ride height. I have dual adjustable Penksi shocks on the rear of my car so I don't run a bar...not needed. When I ran Koni's I had the stock F41 bar on the car 5/16" ? and that worked OK.

 

If QA-1 would make a shorter 700 lbs coil over spring I would test it. But call QA-1 and ask them what springs they recommmend and they are stuck on this spring weight per front end pound chart. they claim that a lapping vette can't even use a 450#. I have the 550# and need to cut about an inch out of it.

I only have one two day regional SCCA event left this year and my main concern is getting my electrical 3 quart Accusump and remote oil filter all installed. My 8 quart road racing pan does not have the oil control to keep oil pressure in the turns. So I have corner "G's" that are way above most of your c-3 vettes