With no spare tire, jack or rear seat my car is very light in the rear. Last week during that one day of rain we got I got sick and tired of slipping and sliding like my back tires were greased. Moderate amounts of throttle at 2000 rpm in 3rd gear would produce wheelspin, and it's serious work to avoid spin from a stop in 1st. (rear is not posi obviously, it's coming soon!)

Since at my work we build heavy equipment trailers, we have plenty of steel lying around, so I decided to make some ballast for the back of my car. I took 4 2 foot pieces of 1" x 5" steel flat bar, had them welded together in pairs, and covered them in black carpeting to match my interior. I dropped those into my rear well after work, adding 150 pound to the very back.

Well, not only has that made a huge difference in driving on wet roads, but on dry roads it has confirmed a suspicion I've had for a while: My weight balance is way too far forward. After ADDING 150 pounds, I have far better balance. In hard enough turns the rear end still steps out first, but it's far more predictable, not nearly as abrupt, and it takes more to get it to come out at all.

I'm definitely going to relocate my battery to the rear, and I already have a fiberglass hood. Anybody know of any other way to lighten the front or shift weight towards the rear? If not, what do I need to do to increase grip on the rear end. So far I'm planning on boxing the trailing arms and replacing the panhard rod with a good tubular one. I already replaced the stock sway bars with a pair of Suspension Techniques bars. How do I need to tune the suspension though? Reduce roll stiffness with a slightly lighter sway bar? Is there any way to get aftermarket springs "mix-and-matched" so I get a slightly softer spring rate for the rear than a standard set?

Any suggestions would be appreciated.


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"Racing is life. Everything else is just waiting." - Steve McQueen - LeMans

305 TBI, T-5. 15.4@92 mph
Member Southern California Third Gen F-Bodies

AOL IM: Andy89RS

 

The real problem is not the weight, it is the suspension in your car. In my Camaro, I have taken out the spare and jack; and have a fiberglass hatch, making about 100lbs taken off the *** -end. With the suspension parts I have, the rear stays put no matter what I do it to, the front end slides out first.

You will need the parts you mentioned, plus an aftermarket torque arm and a good set of adjustable rear shocks and springs. You won't need a larger sway bar, it makes the rear more twitchy-I use an 18mm bar off a base Camaro. For the springs, too stiff is defintely no good, try about 175lb-in on Ground Control adjustable rear spring perches, works like a charm. For shocks, either go Koni or HAL adjustables.
www.groundcontrol.com

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Paul Huryk, billionare in training.
Monkey Guy Racing
Almost part of the moderately infamous NJ in-your-face all goomba crew

Do it right the first time.

Paul's home page

1985 IROC LG4 POS Best: 15.20s at 92.1mph
1984 Camaro 350 LG4 Best: 12.21s at 121.7mph

The smart person pays for something today so that more is received tomorrow.
The ignorant person gets something today and hopes to have enough money to pay for it tomorrow.

 

Paul, I'd also like some help tuning my chassis. I've used your tech articles to guide me in my choices below.

My mods: Kenny Brown SFCs and tranny brace, GW rear control arms, panhard bar (spherical bearings on both ends), steering brace and front and rear springs (640 f, 160 r) and Del-A-lum bushings for front lower control arms, Spohn race version torque arm (front spherical bearing), polygraphite bushings and endlinks

Even with all these mods, my rear end breaks loose before the front. I have 16x8 245/50/ZR16 Firestones Firehawks, and stock WS6 sway bars. I'm wondering what I need to do to get a neutral handling car. I was considering Herb Adams sway bars. Could you further explain why that won't help. Besides that, I'm considering 17x9.5" front wheels and 18x9.5 rear.

Thanks, Dave '91 T/A

 

dnovotny,

In order to get the rear from being so easy to slide out (quicker than the front), you have a couple of choices

First, the bigger the rear sway bar, the more of a tendency the rear has to slide out. The WS6 bar is 24mm (or 23mm), going to a 21mm or 18mm will help a lot (I use an 18mm bar). This is an easy fix-get the bar from a base Camaro/Firebird, $20 for poly bushings.

Second, even though the springs you have in the car are in the ballpark of rate, they can't raise or lower the rear, they are only one height. That is why I recommend the Ground Control adjustable rear spring kit, it allows you to raise or lower the rear without using a stiffer spring, also makes the car ride a lot better.

Third, don't get 18" rubber for your car, it won't help, but will hurt: the tires will be so stiff that the car will skip over the road hitting bumps. The absolute best choice is either ZR1 rubber (275-40-17/315-35-17) or 275-40-17 tires all round, but use a wheel at least 9" wide for a 275 tire. It may be expensive, but the grip increase is considerable.

I know that a properly set-up third gen suspension will pull 1g average on 16" wheels, 17" wheels will put it around 1.05g. FYI: no production "normal" car made pulls 1.05g average. The bigger tires will also allow your car to stop faster too.

If you don't have an STB, get one of theose too.

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Paul Huryk, billionare in training.
Monkey Guy Racing
Almost part of the moderately infamous NJ in-your-face all goomba crew

Do it right the first time.

Paul's home page

1985 IROC LG4 POS Best: 15.20s at 92.1mph
1984 Camaro 350 LG4 Best: 12.21s at 121.7mph

The smart person pays for something today so that more is received tomorrow.
The ignorant person gets something today and hopes to have enough money to pay for it tomorrow.

 

I agree. It's all in the suspension. I have an '81 Elcamino that can out handle anything on the road. Don't belive me? I didn't think so. No one does, well, until they ride in it.

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'82 Firebird, dead stock, 9 bolt disc rear, over 200,000 miles and still going strong, more to come...

 

I'll definitely try out the smaller rear sway bar.

I forgot to mention that I have a Hotchkis STB, and Bilstein shocks and struts. I'll also be putting in a roll-cage soon.

I'm definitely not complaining about the handling. The car is amazing in corners, and all the mods (particularly in the rear), make the car much more consistent, and when I break loose, its gradual vs. stock which was very sudden.

I have two follow-up questions.

One, GW also has a kit to alter rear spring height up to 4 ". I'm not clear how this helps handling and balance besides altering the rears center of gravitly?

Two, I've been told conflicting opinions on 17 vs. 18" tires/wheels. Are you saying that there is too little sidewall with an 18" rim? Is the reason that Corvettes get away with this is because they're IRS vs. solid rear axle?

Thanks, Dave '91 T/A

 

P.S. Paul, thanks for all the feedback.

 

I'll have to experiment with the rear sway bar since both front and rear are Suspension Techniques. A trip to the boneyards to get a few different rear bars and a day of experimentation appears to be in order. :-) About the adjustable rear spring perches: How much are they and do where do I find them, www.groundcontrol.com didn't take me anywhere.

 

I definately recommend a posi, it will tighten the car up coming out of corners. The lighter way bar will help too, especially if you are running stiffer springs. If you know anyone with a set of race scales (or 4 grain scales) i strongly suggest that you cornerweight the car.

 

The link is www.ground-control.com

The perches and springs are about $200, but you can buy extra pairs of srings for $110 a pair. I went for the 150lb-in, but a stock weight third gen would probably need 175lb-in not to bottom out on big bumps.

The GW kit has been in the testing stages for the last 18 months, so I bought the ground control ones. I think GW only offers one or two spring rates, ground control offers many more.

The reasons why the Vette uses 18" wheels:
One, it uses a tire 1" taller, so the sidewall is the same as the old 17" from the 1989-1996 Vette, but 1" taller (26.5" vs 25.5")
Second, the IRS helps a bit, but they don't ride like Cadillacs either. The IRS actually gives the car more control over bumpy roads. On smooth roads, it offers no real advantage.

------------------
Paul Huryk, billionare in training.
Monkey Guy Racing
Almost part of the moderately infamous NJ in-your-face all goomba crew

Do it right the first time.

Paul's home page

1985 IROC LG4 POS Best: 15.20s at 92.1mph
1984 Camaro 350 LG4 Best: 12.21s at 121.7mph

The smart person pays for something today so that more is received tomorrow.
The ignorant person gets something today and hopes to have enough money to pay for it tomorrow.

 

a couple of years in the TransAm series has taught me a little.
1. Softer equals More bite
This is true front or rear, the term softer applying to springs AND swaybars.
2. Factory cars are severely nose heavy
The more percentage you have in the rear the better. To a point (a point we'll never achieve on one of these cars driven on the street)
3. Your tire is a spring too. The higher rate it has, the less grip it will have.

I knew a guy who purchased the national solo II champion car. It had stock berlinetta springs in the rear that were cut for ride height. The theory was that he needed the extra grip.

probably doesn't help much but it's something to think about
Clem