ive got a bone stock 89 that ive learned pretty well at autocross. im running vet brakes advanced street alignment and 275/35/18s all around (bridgestone potenzas). what are my current sway bar sizes? the car handles pretty neutral but could be crisper into turns. what kit should I go for? there seems to be more front than rear sway bar kits. or maybe poly bushings will do the trick? Ive thought about getting a set of slicks but its expensive and will change my class. pretty sure a front sway bar wont change the class. scca considers my car b street prepared. I think they pick these classes out of a hat.

 

Is your car a z51?

 

There's a really simple adjustment you can make at the track that's easily returnable and you'll be amazed at the difference it will make even on a stock suspension. On the front upper control arms, pull two 1/8'' shims from each control arm attachment point (4 total attachment points, 8 total shims). This gives you more negative camber and at the same time gives you toe-out which is what their autocross specs call for. On the rear, screw each toe control rod out of the rod end 4-6 flats (or two thirds to one full turn) to give you the toe-in to counter the increased bite from the front toe-out. Adjust the amount of shims/rear toe control rod flats to achieve your desired turn-in/balance, you may find 8 shims from the front is too much if the course has cornering speeds above 60-70 MPH...just keep track of what you do so you can return it to the original adjustment at the end of the day.

I would prefer to see your rear alignment at 1° negative camber and 0'' toe for the starting point...the camber is more desired for the track and the 0'' toe will minimize tire wear on the street. Then all you have to play with is the toe adjustment although you may find you have to go more than 6 flats to achieve the desired balance. As you increase front toe-out, the front ''bite'' increases to a point where the rear can't keep up which is where increasing the rear toe-in comes into play...that's what I mean by balance. The rear toe-in increases the slip angle of the outside rear tire in a corner which allows the rear to contribute more to the total cornering power and keeps the rear planted instead of sliding. You'll find you can roll into the power sooner coming off a turn and the rear is significantly more ''planted'' which increases your confidence level in the car's resistance to ''spinning'' which means you can explore the car's handling limits safely and come closer to approaching the ultimate limit.

It goes without saying that all of your suspension bushings, ball joints, tie rod ends, and wheel bearings are in good to excellent shape. Any attempt to change springs/bars/alignments will just aggravate/amplify any bad components in the ''system''.

For mods, my opinion (and everyone has one) is to use the biggest stabilizer bars at each end you can find and adjust spring rate to balance the bars. Use poly or not, I have a mix on my car depending on where they are...stabilizer bars get poly and control arms don't. Using the factory rubber control arm bushings retains the original design compliance understeer on the front and rear suspensions which I like...it's a personal choice so don't think one way or the other is right/wrong. The poly bushings will produce the same type of compliance understeer just to a much lesser extent...one day, I might make the change.

 

I dont think so

 

I really dont want to start messing with the alignment myself because this is my daily and the car actually tracks nicely going down the road. I mean i guess i can just put the shims back and turn the tie tod back to where everything was. Now when you say adjust spring rate,
You mean changing to stiffer springs?

 

I have a nice 24mm rear bar with new VBP poly bushings on it for sale in the C4 section. This was for my 92 but went another route.

 

What is the stock size? If i only do the rear wont i oversteer more? I like the way the car handles now, its pretty neutral. So shouldnt i increase the sway bar sizes consistently? For example, if i go up 2 mm in the back i feel like i should go up 2 mm in the front as well. I dont want to change the characteristics of he handling, i just want to improve the limit

 

Open the panel behind your driver seat and read the codes too see what suspension you have.

http://www.corvetteactioncenter.com/...usp_chart.html

 

Just read my attachment. It will answer many questions you have.

 

I cannot find any suspension codes on this thing. will my vin number be of any help? 1G1YY2185K5125280

 

I have a base 89 coupe too. Your option codes are on a sticker under the center console armrest. You'll find a code that's says either FE1 or Z51. They're in alphabetical order. The base FE1 suspension has a 26mm tubular (hollow) front sway bar and a solid 22mm rear and softer springs and shocks vs the Z51 suspension. Z51's have 30mm solid front sway bar and 24mm solid rear sway bar. I upgraded my front bar to a VB&P 32mm solid with poly bushings and bought a 24mm rear bar off Ebay that I still haven't put on yet (I always have something going on!). My base springs are lowered with wedges and I have crappy KYB shocks that a previous owner put on. I went to an autox in March and the 32/22 sway bar combo was actually a very neutral balance. The shocks were horrible. Needing some Bilstein Sports soon. Long story short, if you want less body roll and crisper turn in, I recommend the 32mm front bar. Some will tell you it's going to make it push but mine doesn't push at all. I'll give you another opinion about push after my first track day at NCM Motorsports Park in September!

 

Look for the following codes:
FE1 (standard), FE7 (heavy duty suspension) FX3 (adjustable) Z07, Z51, Z52 (special suspension packages) and then look at the chart that was referred to previously. RPO's are here http://forums.corvetteforum.com/c4-g...4-rpo-faq.html and may help with this and other questions about your car.

 

Im assuming mine is a base. Somebody replaced this interior at some point and there are no codes anywhere. Anyway thanks for the swaybar feedback. Im definitely gonna go for a 32mm solid front bar.

 

Since there's no RPO code sheet for you, if you really want to know then you can pull the springs and see what code they have stamped in them, and someone can tell you what the code means... it's not an RPO code nor is it listed in the suspension chart, but there are others smarter than I who possess this information

You can also measure your current swaybars and compare that to the suspension chart. It may offer info as well. Of course both these options only work if no previous owner changed any of it.

Happy Vettin

 

Yes, I mean change to stiffer/softer springs to get the roll stiffness balanced.

For the alignment, only you will be able to determine the level at which you want to autocross. If you do it for fun and aren't worried about how you place, then leave the alignment alone.

 

How much pressure are you running in those tyres?
Please don't tell me 28-30psi.
I'd be running 40-42psi in them.

 

*crawls under car and looks for shims*

 

I was running 36 front and 34 rear. I think i had too much. The arrow on the tires to show where its supposed to be scrubbing was about a quarter inch away from the scrub marks

 

While im buying the sway bars from vette brakes, should i go for the lowering kit? I just dont want my car to ride like a vw jetta.

 

Not a chance.