Would like to get some opinions here before I make an adjustment. Here is the data; have @ 600lb rear spring, 26mm solid bar, VB&P heim jointed suspension components, and Koni Sport shocks.

I installed the Koni's last year but only got to run one time in an Low speed AUTOX. It seemed to handle very good. After that the engine went so didn't use for the rest of the year. At the original time of install of the Koni's, I left them on the soft setting.

Since I have the engine back in now, I have driven on the street a couple of time and it seems a little bouncy in the rear. Is this just because of the streets or do you think I need to adjust the Koni's to a firmer setting?

 

I would definitely adjust them to a firmer setting. I have the same shocks and with the BASE, '92 suspension, I feel that I get the best ride with them set about in the middle of the adjustment range. Any softer, it is smoother, but more "boundy"...just not enough rebound control, IMO.

Frankly, I don't think the shocks have enough compression damping, either.

 

Go two clicks higher.
I use the same setting front and rear.
You may find your needs are different

 

I was thinking the same thing. Just wanted to get some feedback before pulling them to adjust. It kind of s$@ks that the adjustment is on top and you have to pull them to adjust.

 

Thnx. Going to go to medium setting. I had the front on medium already and made the rear soft.

 

600 lb spring?

That's GOT to be a mistake....A 600 in/lb spring won't "bounce". In fact, it won't even bend.

The famed 84 Z51 rear spring was ONLY 499 lbs/in and that was just a hair from being solid. I have a 411 that has so far knocked out most of my fillings and damn near ruined both kidneys....
I am 250 lbs, and I can lay that 411 on the floor, and jump on the thing and NOT get ANY movement out of it. Like jumping on a 2x4. Edgewise.

The avg spring rate for stock street C4s in in the 200's. Firm begins @ 300, rock hard @ 400.

If someone is selling springs claiming they have a 600 in/lb rate ....they're stretching the facts a bit or they have a new method of testing spring return rate that nobody else has!

 

Clicks? Mine don't click. It's an "infinite" adjust.



I'm sure you know this, but the fronts you can adjust w/o removing. Rears, I just remove the tops, adjust and then stuff back in and bolt up. It is a PITA, but I wouldn't remove the shocks. I think I'm going to drill my frame and make a tool so I can adjust the rears from inside the car.

 

Speaking of "fabrication" - how's the CTS-V shifter doing?

 

When you say "bouncy", is it too soft and floating, or is it too hard and skipping over bumps? From your description I can't tell which condition you have.

If it is too soft, the shock adjustment may help.

If it is too hard, then the 600 in/lb rate may be just too stiff for bumps in street driving.

 

It's great now, but I did have to make some adjustments. Having the shift **** offset (toward the driver) from the rubber isolator put too much torque on the rubber when shifting and it kept tearing the rubber isolator free of the base shifter rod. I couldn't find an adhesive that could manage that much torque given the amount of surface area between the isolator and teh 1/2" diameter lower rod.

Also, my "gate" grooves were a little short in 2nd so it didn't want to go all the way into second.

I used a die grinder to lengthen the 2nd gear gate, and changed the geometry on the upper shift lever so that it didn't apply tq to the rubber isolator when you shift it, and it has been working beautifully since. It feels great, positive and well defined, with zero play when in any gear. Never miss gears now, it always goes right into reverse and 1st (previously you couldn't find either at all, sometimes!)...I'd say that is was successful. I still feel that the BEST way to manage the shifting on that trans would be to directly manipulate the internal rail from the shifter rod, and have a gate on the rod (like I did) to provide limit/gate feel and stops. But for the contraption that it was, it came out pretty good and it's a massive improvement over what it was. My benchmark was a Pro 5.0 on a T5 or T56 in an f-bod. I'd say I got 90% of the way there with what I did.

 

654 lb/in custom order

Thanks for the tip, I'll try that.

It is stiff and not really set up to drive on the street. Just trying to get dialed in as best possible before getting on track. And when autoxing it may seem fine, but may be giving up a few 10ths of a sec and that can be the difference between winning and losing.

 

sounds to me like its "skipping".....not bouncing.

 

I will post findings after I adjust the shocks. It may be a couple weeks.

 

Too stiff i think but i ran the rear 84 z51 for an entire season and did good. The trick i had to keep the jacking and bounce down was a full tank of gas and the entire spare and jack kit still in the rear. + a big *** wing. (she thinks she can fly)

Also check to see your not smacking your bumpstops. sometimes they need a little trim.

 

that's awesome! I was essentially troubleshooting my current setup as well. I have an 84' Z51 rear spring (88' z51 front spring), with the stock Bilstein's, and over dips with a sudden lip/bump, the darn thing wants to launch me through the targa top (I weigh 240)! I've come to the conclusion that I need to get a more aggressive shock valving to compensate for the heavier spring. At this point, it can be dangerous, since the spring is so stiff. Almost makes the car feel unpredictable over unexpected dips, humps, etc.

 

Please explain this. How does an 84 have "jacking". And after you explain that, please explain how that is any different than any other MY C4....

 

OMG!!! 911! I am trying to IMPROVE my '89 suspension.I am about to pull the trigger on a SPORT spring rated at 480-510 lbs. That suddenly sounds WAY too stiff.Checking the rate on my new front SPORT spring but what are reasonable rates for the street?

 

As a starting point check out the stock rates in the chart at: http://corvetteactioncenter.com/tech/c4/susp_chart.html
It will at least tell you where the factory started. Note that the suspension changed in '88 and the spring rates before and after don't match each other. How much you change from there for an upgrade or track use depends on your use.

Good luck.

Note
To compare the chart values in N/mm to the lb/in used in this discussion, multiply the chart values by 5.710147. (or 1 N/mm = 5.710147 lb/in)

 

I talked to Jeff Schwartz at Schwartz motorsports when he was at Scottsdale for the Good Guys show at the track they had there, and he said he is moving in the direction of softer springs and stiffer shocks and heavier sway bars because of the "bounce" factor.

 

My 96 has the Z51 springs and sway bars. It handles good and drives good on the street.

If I were just running on the street, and wanted a little better handling, I would add larger front and rear anti-roll bars and good shocks. One other thing I would do is get the ride height lower by lowering the front end and rear.

Of course the bouncy suspension can have it's place in certain situations. If you have the right passenger