I'm stock piling parts for the suspension rebuild and am looking for advice on the sway bars. I'm building a cruiser, but of course want it to handle like a vette should, I'm also adding about 200hp over stock and want it to perform safely if I ever decide to push it. I'm considering the tubular bars from VB&P, is there a noticable harshness with the larger bar vs the smaller?

Also, I've heard it said here several times that no rear bar is best, can anyone elaborate on this specifically for my intended use mentioned above?

 

too stiff a rear bar will produce oversteer, hence the recommendation of not having a rear bar. with your additional power, if you power out of a corner, you could swap ends really fast. the gm engineers used a 9/16" rear bar on the bb vettes with a 7/8" (i think) at the front. i'd probably stick to their choice.

 

I'll do my best to help you out here.
A little theory first. The sway bar is a mechanical link between the left and right spring. It transmits cornering loads from the outside (doing 95% of your turning) to the inside (doing a whole of nothing).
With a thick bar vs. thin, there is no difference in a straight line. If both left and right sides are compressed, then the sway bar does nothing. It just goes with the flow. However, once you throw it into a corner, the bar will transfer the load. A twisting bar is a sping in itself (just like a torsion bar suspension), so the thicker it is, the more of the load is transmited. Have you ever seen a VW GTI doing a three-legged stand in a corner? the inside wheel can sometimes lift on the rear since the springs are soft (better ride) and the sway bar is thick (better cornering).
There tend to be two schools of thought: thick bars, soft springs or thin bars strong springs, both with their pros and cons. That's a whole other discussion.
When it comes to balance, however, too much sway bar can hurt. If you go too thick or the ratio between front and back is biased too much, that end of the car will tend to slide. If the front is too thick, understeer; if the back is too thick, oversteer. I feel a lot of guys go no bar in the rear so they are in a safer set up (understeer). I could be wrong about that.
I would call a reputable vendor and ask them what they think. I like VBP as I bought a full suspension kit from them and are pleased with the results so far. Some people don't like them anymore, so ask around. I hope this cleared up some issues and didn't make it worse for you. Good luck with the build!

 

Great advice and explanation! The BB cars had rear sway bars to offset the nose heaviness of the car. I know the late 70's vettes with the performance/sport suspension had rear sway bars. My 78 had a 1 1/8in front bar with a 9/16in rear bar from the factory and setup from GM for predominately understeer characteristics as you said since it is safer for the average driver. All GM cars at that time were designed for understeer after the corvair fiasco. With that said I definitely do not subscribe for the street the idea of no rear sway bar. All kinds of theories have been put forth for the no rear sway bar crowd such as "it hurts the functioning of the IRS" (Not true) to the "car will swap ends easier" (true if you go too far on rear bar size versus the front) and don't understand handling dynamics. Part of the issue with the vettes is that the cars from the late 70's have almost a 50:50 weight distribution ( a great feature) versus most the cars at the time being nose heavy. In fact, my 78's weight distribution from the factory is 48% front and 52% rear which means if you over cook it in a turn it is more likely to swap ends than a traditional vehicle if you do not know what your doing (big throttle inputs at the limit or pedal "snapping" (lifting off abrubtly) in a high limit turn. With that said, if you want to balance the handling to a more neutral attitude than stock versus the predominate feature of understeer, you need to go slightly bigger on the rear bar which is why many of the vendors offer suspension kits with bigger rear bars. On my 78, I kept the front 1 1/8 in bar using poly mounting and end link bushings and went to a 3/4in rear poly mounted bar, instead of the 9/16 in bar. The car's handling is very neutral but could bite if pushed too hard (beyond 10/10th's driving). These issues though are no different than pushing a Porsche or Ferrari beyond its limits. If you make sure that the bars are "balanced" you will be pleased, in my opinion.

 

My 79 had an original suspension configuration with no rear sway bar and a 1'' sway bar in the front. I installed an Addco small rear sway bar and increased my front sway bar size to 1 1/8''. Handles fine. Was it needed? I don't really think so because most of my driving is cruising.

 

All this talk about "swaping ends"... You guys need to drive a modern racing kart. You will get a totally new perspective on what "easy" to swap ends is.

Anyone in the DFW area that want's to try one out should PM me.

 

I agree with your comments about swapping ends. I have owned my 78 since 1983 and have talked with countless vette owners over the years and it was not until I joined the forum did I ever hear so much talk about "swapping ends" and "no rear sway bar on vettes" talk. Most front engine cars with or without independent rears will benefit from a balanced front AND rear sway bar package on the street. I am amazed that there is so much chatter on the subject especially since vettes and countless other sports cars and sedans have come from the factory with front and rear sway bars FOREVER! THERE IS A REASON FOR THAT!

 

A couple of things that should be understood about bars before messing with them...

The addition of bar, while reducing roll, increases lateral weight transfer, which tends to reduce grip at the end of the car in question except in the case where excessive roll is itself causing detrimental alignment issues during suspension travel. Thus, a stiffer front bar will tend to increase understeer, and a stiffer rear bar will tend to increase oversteer. This is often misconstrued to mean that one should simply add rear bar to solve for too much "push", when the better approach would be to take measures to improve grip on the front where it is lacking, adding bar only as required to fine tune balance.

A more stiffly sprung chassis requires less bar to check roll, and an adequately sprung C3 (even a BB) does not necessarily require rear bar. However, as GM apparently surmised, many would have complained about the ride quality of a more heavily sprung BB/C3. Thus, IMHO rear bar was added as a crutch against the extra engine weight in lieu of yet stiffer springs. Myself, I've followed Guldstrand's advice for 860# front coils (on the street, no less), std front bar and no rear bar, which has proven to be a successful setup without complaint.

It's prudent to sneak up on balance at the limits from understeer than from oversteer. On the street, a car that snaps into oversteer should you be forced to give up the throttle while cornering hard (it's called "trailing throttle oversteer' or "TTO") can result in a lot of expensive noises and may get you hurt, so I wouldn't go slapping rear bar on a cruiser just because someone else has installed one, with success or otherwise.

 

I installed mine as more of an experiment then anything. Are you saying that my approach has accomplished more negative then positive? I honestly have not had a chance to toy with the installed sway bars yet but plan to later this year. What would I be trying to accomplish with proper adjustment and installation? Any suggestions on proper adjustment and testing?

 

1 1/4" solid up front with a 3/4" rear out back. Perfect balance of steer for me. Depends on the spring rate too. I have 630s up front and a 360 out back. Now I'm going to get out of here before Skunk yells at me again.

 

I'm not going to yell at you, enkeivette. As I believe we've established before, this isn't a one-size-fits-all situation, since not everyone agrees as to what is an acceptable compromise between ride quality on the one hand and handling on the other, or to what proper balance is. I realize that spring rates such as those I run are out of the question for many who consider it an intolerable proposition to trade off comfort for maximum cornering capacity (IMHO it's not really that harsh). I'll even go so far as to say that standard bar(s) aren't enough with standard springs, but must maintain that beyond the point at which sufficient roll control has been achieved it is just as easy to put on too much bar and end up with less than optimal handling. (Now, was that so bad? )


That said, what I wish to point out more than anything else is that going about this stuff haphazardly could have you chasing your tail, both figuratively and literally. No, the best way to optimize handling and driveability to suit one's needs is to first establish (carefully) what traits the car has and then to address it's shortcomings. For most, I'd suggest that there's likely no better environment in which to do this than at an autocross or HPDE event. Take small steps towards the limits, especially if you're a novice and/or don't quite know where they are, and just pay attention to what the car is trying to tell you. In any event, don't even bother if you have alignment issues or worn out suspension components, as the info you'll get may not be accurate. Further, bear in mind that the best setup against the clock may not be advisable on the street, and be ever so aware that a car's personality at the limits may well not be that which one has come to expect thru less spirited driving. Lastly, don't let preconceptions blind you.

 

In my prior comments on this subject, I was careful to include the key words "on the street". Racing is a totally different animal if one has been on the track. Many of the above comments relating to swaybars and spring rates are fairly accurate. Since most people don't run really high spring rates on the street due to the deterioration of the ride quality, balanced sway bars are an absolute necessity if you are looking for optimal handling. With street spring rates, it is almost impossible to achieve optimal handling without a rear sway bar on a corvette or even most sedan including front drivers that are very nose heavy. I really doubt GM added rear sway bars because customers would complain if they had not. You really have to be VERY careful about drawing analogies and comparison to race setups for street driving. They really are two different animals!

 

Due to variations in weight due to options and springs, TESTING at the track or during an autocross is the only way to really know...

With my '78, I thought I was pretty well balanced, but at Hallet during NCCC Convention, I found that I had to ease the throttle in the faster turns due to oversteer limiting the rear tires' adhesion. When I disconnected one of the rear sway bar links, the car tightened up a bit and was considerably faster.

The car is configured with 1 1/8 front bar and slightly shortened front springs (~450 lb/inch); the rear has a 9/16 rear bar (now disconnected) and a 360 lb/inch fiberglass rear spring. Mass items include A/C, 4-point roll bar, and spare tire.

Going back a few years (decades!), I put a 3/4 inch rear sway bar in a '65 small block Vette with a stock 7/8 inch front bar - it was scary on the very first off-ramp turn-off as it wanted to swap ends at the slightest provocation - I really learned from that.

Borrow a rear bar and TEST it first - I'm sure there are a lot of larger bars cluttering the garages of those who have been through this. Once you try it and have seen what the other side feels like, you will know what to avoid - unless you want "style points" for drifting or spinning!

Hope this helps

 

I gotta tell you guys, without adding SIGNIFICANT power to the motor, it's kinda hard to swap ends anyway.



Let's face it, stock motors on 75 and up don't even chirp a decent pair of tires when going from 1st to 2nd, without power shifting, and most folks tend to not power shift in a turn.

To put it into perspective, I have also driven a 300 hp camaro, and again, while she did have a tendency to fish tale if you go into the turn too hard, I would shudder to think how stupid you would have to be in order to actually flip her around.



Not saying this to take the issue lightly, but I think some of you guys are coming from the perspective of auto crossing, or some other form of track racing, and from the perspective of driving with a LOT more power than this dude is going for.

 

A long subject, and EVERYONE has a opinion. There are alot of veribles involved. So here's my experience.
69 BB 390 hp. I went with the VB&P suspension upgrade. 550 lb fr springs and 360 lb composit rear spring. 1 1/8" or 1 1/4" ( can't remember exactly) front bar and I think a
3/4" rear bar. The car had ALOT of oversteer. After 8k-10k miles, and reading about this on this fourm, I removed my rear bar. I now have neutral steering. Much, much better.
Like I said, it appears that there are alot of veribles, hp, tq, weight, tires, driving styles, etc., so my suggestion is to get a large front bar, then get a rear bar if needed. I think the rear bar is pretty much a try it and see situation. Too big and you get oversteer.

 

KevinK, please don't take this as flames, but apparently you don't recognize that excess power application is NOT requisite to oversteer, and that the type of power oversteer to which you refer in your post does NOT necessarily indicate an inherent oversteer imbalance. Further, I can personally vouch that you don't have to be pounding around a track to find yourself watching the big panorama go by if you lean on a car with an unforgiving setup, and I would hazard a guess that TTO rather than too much loud pedal has been responsible for a good number of spin-outs among other C3 owners such as myself who have BTDT.

 

I think another problem with a sway bar/suspension discussion is a lot of people don't really have a handle on what neutral steer really feels like. I've been in a few cars where people have claimed that the car was neutral, but in reality plowed like a tractor. Most people are comfortable with understeer and mislabel it as neutral. Neutral steer is pretty hard to nail down. I find it analogous to balancing a marble basketball.

 

Nah, I new I would catch some heat when I made that comment. I don't know, after driving mine around for a bit, it just seems like it would be pretty hard to lose control of it...

 

Bare in mind this is coming from a guy who went from driving a 300ZX to a 76 corvette.....



The 300 being FAIRLY easy to spin, the corvette being a challenge just to fish tale a little.

 

Geesh the Sway bar discussion again. I only use my car for Auto X and do not use a rear bar. If I did I would have to go slower. What those of us who race our cars are trying to tell you who don't, is someday you might get in an emergency situation where a rear bar is going to get you in trouble. A car with a small amount of understeer is much more controllable...you drive with the front wheels, than a car that is trying to steer with the rear.