Before the next auto-x I think I'm gonna go ahead and replace the sway bars and rear shocks. Gonna go ahead and get the KYB GR2s from summit for the shocks but I need some advice on the sway bars.

Input is appreciated.

 

Hi,
Seems that previous forum members with '81's have had good results with a 1 1/8" up front and a 3/4" at the rear. This seemed to be a common setup regardless of the spring rates used (wouldn't different spring rates possibly need different sway bar sizes? ie. with really stiff springs then a smaller bar would be better?).
When I eventually get round to fitting a rear sway bar I was thinking of going for something a bit smaller than 3/4" (maybe 5/8"?). My logic (probably flawed!) is that the balanced sway bars (1 1/8" with 3/4") give flat cornering, but if you push it too hard then any/all tires could let go with very little warning. Allowing a little bit of roll at the rear should (could?) allow a bit more loading on one rear wheel than on the other. Hence pushing it too far will result in one rear tire starting to slip, giving you some warning that things are getting a bit out of control. The smaller rear bar won't allow quite as high cornering speeds, but if you've ever dropped your bike from pushing it further than the tires can cope with then you'll know where I'm coming from (the land of expensive repairs & bruises!).
Gator81 spent a lot of time improving the handling of his '81 using the basic stock design. Balanced sway bars, 460lb front spring, 330lb(??) rear composite, poly all round, etc, etc, & each modification/improvement allowed him to take his favorite "test bend" slightly faster. What he wasn't prepared for was the huge difference in cornering ability that fitting decent, modern tires gave. He threw on a set of Pirelli Scorpion Zero's which dramatically improved both the cornering and the ride quality (cornering improved so much that he was still accelerating when his favorite bend ended). When I (eventually) get onto handling improvements the 1st thing I'll do is change tires

 

1-1/8 front, 5/8 rear. A bigger rear bar may lead to oversteer.

 

don't waste your money on the GR-2's. They suck I had them and have upgraded to Blisteins..

carbster

 

What size is the front bar on the FE7 package? I think it was like 1.12, which is about 1 1/8". If that's so, then I just need to get a bigger rear sway bar.

As for shocks, I'll probably get bilsteins when I get a composite spring.

 

I just upgraded my front sway bar to 1 1/8 in the performance plus package, i would run a 3/4 in the rear if i hadn't purchased the dual mount rear spring. Also got blisteins sport shocks in the kit. I'm happy.
Tires are very important too.
You can go to www.tirerack.com and check out whats available, ratings, and user thoughts along with having the best prices and great shipping.
Good luck.

 

Why can't you run the rear sway bar with the dual mount? I thought the sway bar brackets bolted to the trailing arms.

 

The factory JimKunna (Gymkhana), FE7 has 1 1/8" up front and 7/16" in the rear. Also had 550 lb spring in the front and 7 leaft in the rear. No idea as to what the spring rate was. It also had different shocks to go along with it. The rear bar is very tiny to say the least. However, GM thought that was a pretty good combo. In my opinion the rear bar is weak. It twist easily by hand, unlike the front bar.

 

Being that mine is an '81, the FE7 actually had a 9 leaf rear spring, instead of the 7. But basically, I can leave the front one alone and just replace the rear with a 5/8"? Which composite spring would do the best in the back with it? I'm assuming the 330lb. composite would probably work well, but I'm still learning a bit.

Like I've stated, eventually I'm going to do the front monospring conversion and bilstein shocks all the way around. That's quite a bit further down the road, though. Probably not until christmas, even.

 

From what I've heard from people, the '81 works well with a 330lb composite spring at the rear (with applicable shoks) & a matched pair of sway bars (1 1/8" front, 3/4" rear). I don't know if that includes the stock front bar as I've heard that some sway bars behave differently to others of the same size from a different manufacturer eg a 1 1/8" stock GM one may have more/less flex than a 1 1/8" from somebody like VB&P? I've got no personal experience of this, but there was plenty of talk about it when I 1st joined this forum. I do know that a couple of people are very happy with a 330lb composite rear spring when matched up with 460lb front springs on L81's. Again I've got no personal experience & those people may well be happy to put up with a hard ride in the interests of flatter/faster cornering? It was from talking to a couple of those people that I decided that a smaller rear bar than 3/4" is probably the way to go for me (my reactions aren't what they used to be!). The comment that matched bars give excellent flat cornering, at faster speeds than stock, sounded good to me. The following comment "But if you push it too far then you don't get any warning & "BAM!", you'll go **** first into a ditch". Well, the ditches here are deep & contain old mature Oak trees, I don't want to take a closer look at them, hence the idea of a smaller rear bar

 

Big G has it right - 1 1/8 up front, 5/8 rear.

This combo is very good for general driving without inducing oversteer with OE sized street tires. I realize that many run a 3/4" rear bar but most of these folks also run oversized 15s or have upgraded to 17" wheels and tires.

Believe me, I've been there, hard cornering on OE size street tires with a 3/4" rear bar WILL oversteer and probably result in a spin. At best, you will be embarrassed on the Auto-X course. At worst...........

You cannot compare bars from different manufacturers since several use different length lever arms. Look at illustrations of GM sway bars and compare to VBP or Herb Adams or Guldstrand sway bars. You will see that they have different length lever arms and different methods of atttachment. Consequently a smaller diameter GM sway bar with a longer lever arm is equal to a VB larger diameter sway bar with a shorter lever arm.

There has been a lot of discussion on this over the years so check the archives. Long ago I posted the formula needed properly compare antiroll resistance of different sized sway bars. It is in the archives somewhere.

Roll resistance is not linear. You will be amazed at the difference in roll resistance from a small increase in bar diameter. For instance, a 3/4 " bar has more than twice the roll resistance of a 5/8" bar.

One other point, an oversized rear bar will reduce the IRS to responding more like a fixed axle vehicle - not what Zora had in mind......

 

When you use our rear dual-mount spring system, you can eliminate the rear sway bar if you so choose. Those who wish to put larger wheels and tires on their Corvette or want additional weight savings, sometimes choose to eliminate the rear sway bar to get additional clearance area in the rear and loose about 12-15 lbs.. Our rear dual-mount spring system mounts to the crossmember with the dual brackets off from center. This mount and spring set-up acts like a rear sway bar eliminating body roll so you can use it as a replacement.

Pattie
VBP

 

Is it just as good as having a sway bar with the dual mount?

 

I'm sure VB has good reason for stating the above, but the logic is not apparent.
Clearly a dual mount eliminates cross talk from side to side but that would seem to require a bar, not eliminate it.
Maybe some CF contributors who are using the dual mount will weigh in on this.......

 

Good reading here...

http://en.wikipedia.org/wiki/Corvette_leaf_springs

 

Excellent post. Thanks.

 

Doesn't VBP have Hollow Sway bars on the market? Which ones would be good for a slightly upgraded car with 16" wheels? What about weight savings etc?

carbster

 

That answers my question. thanks

 

I think the hollow bars are for C4s,5s and 6s. Per the excellent article above, a dual mount composite spring will offer some anti roll resistance and require an antisway bar that has less resistance. The reduced cross section of a hollow bar will do that.